diff --git a/en_US.ISO8859-1/articles/releng/article.sgml b/en_US.ISO8859-1/articles/releng/article.sgml index 75183f532f..ce4010c119 100644 --- a/en_US.ISO8859-1/articles/releng/article.sgml +++ b/en_US.ISO8859-1/articles/releng/article.sgml @@ -1,1046 +1,1046 @@ %articles.ent; The Release Engineering of Third Party Packages'> ]>
FreeBSD Release Engineering November 2001 BSDCon Europe Murray Stokely I've been involved in the development of FreeBSD based products since 1997 at Walnut Creek CDROM, BSDi, and now Wind River Systems. FreeBSD 4.4 was the first official release of FreeBSD that I played a significant part in.
murray@FreeBSD.org
$FreeBSD$ &tm-attrib.freebsd; &tm-attrib.cvsup; &tm-attrib.intel; &tm-attrib.xfree86; &tm-attrib.general; This paper describes the approach used by the FreeBSD release engineering team to make production quality releases of the FreeBSD Operating System. It details the methodology used for the official FreeBSD releases and describes the tools available for those interested in producing customized FreeBSD releases for corporate rollouts or commercial productization. Introduction The development of FreeBSD is a very open process. FreeBSD is comprised of contributions from thousands of people around the world. The FreeBSD Project provides anonymous CVS[1] access to the general public so that others can have access to log messages, diffs (patches) between development branches, and other productivity enhancements that formal source code management provides. This has been a huge help in attracting more talented developers to FreeBSD. However, I think everyone would agree that chaos would soon manifest if write access was opened up to everyone on the Internet. Therefore only a select group of nearly 300 people are given write access to the CVS repository. These committers[6] are responsible for the bulk of FreeBSD development. An elected core-team[7] of very senior developers provides some level of direction over the project. The rapid pace of FreeBSD development leaves little time for polishing the development system into a production quality release. To solve this dilemma, development continues on two parallel tracks. The main development branch is the HEAD or trunk of our CVS tree, known as FreeBSD-CURRENT or -CURRENT for short. A more stable branch is maintained, known as FreeBSD-STABLE or -STABLE for short. Both branches live in a master CVS repository in California and are replicated via CVSup[2] to mirrors all over the world. FreeBSD-CURRENT[8] is the bleeding-edge of FreeBSD development where all new changes first enter the system. FreeBSD-STABLE is the development branch from which major releases are made. Changes go into this branch at a different pace, and with general assumption that they have first gone into FreeBSD-CURRENT and have been thoroughly tested by our user community. In the interim period between releases, nightly snapshots are built automatically by the FreeBSD Project build machines and made available for download from ftp://stable.FreeBSD.org/. The widespread availability of binary release snapshots, and the tendency of our user community to keep up with -STABLE development with CVSup and make - world[8] helps to keep + world[8] helps to keep FreeBSD-STABLE in a very reliable condition even before the quality assurance activities ramp up pending a major release. Bug reports and feature requests are continuously submitted by users throughout the release cycle. Problems reports are entered into our GNATS[9] database through email, the &man.send-pr.1; application, or via the web interface provided at . In addition to the multitude of different technical mailing lists about FreeBSD, the &a.qa; provides a forum for discussing the finer points of release-polishing. To service our most conservative users, individual release branches were introduced with FreeBSD 4.3. These release branches are created shortly before a final release is made. After the release goes out, only the most critical security fixes and additions are merged onto the release branch. In addition to source updates via CVS, binary patchkits are available to keep systems on the RELENG_X_Y branches updated. discusses the different phases of the release engineering process leading up to the actual system build and describes the actual build process. describes how the base release may be extended by third parties and details some of the lessons learned through the release of FreeBSD 4.4. Finally, presents future directions of development. Release Process New releases of FreeBSD are released from the -STABLE branch at approximately four month intervals. The FreeBSD release process begins to ramp up 45 days before the anticipated release date when the release engineer sends an email to the development mailing lists to remind developers that they only have 15 days to integrate new changes before the code freeze. During this time, many developers perform what have become known as MFC sweeps. MFC stands for Merge From CURRENT and it describes the process of merging a tested change from our -CURRENT development branch to our -STABLE branch. Code Review Thirty days before the anticipated release, the source repository enters a code slush. During this time, all commits to the -STABLE branch must be approved by the &a.re;. The kinds of changes that are allowed during this 15 day period include: Bug fixes. Documentation updates. Security-related fixes of any kind. Minor changes to device drivers, such as adding new Device IDs. Any additional change that the release engineering team feels is justified, given the potential risk. After the first 15 days of the code slush, a release candidate is released for widespread testing and the code enters a code freeze where it becomes much harder to justify new changes to the system unless a serious bug-fix or security issue is involved. During the code freeze, at least one release candidate is released per week, until the final release is ready. During the days leading to the final release, the release engineering team is in constant communication with the security-officer team, the documentation maintainers, and the port maintainers, to ensure that all of the different components required for a successful release are available. Final Release Checklist When several release candidates have been made available for widespread testing and all major issues have been resolved, the final release polishing can begin. Creating the Release Branch As described in the introduction, the RELENG_X_Y release branch is a relatively new addition to our release engineering methodology. The first step in creating this branch is to ensure that you are working with the newest version of the RELENG_X sources that you want to branch from. /usr/src&prompt.root; cvs update -rRELENG_4 -P -d The next step is to create a branch point tag, so that diffs against the start of the branch are easier with CVS: /usr/src&prompt.root; cvs rtag -rRELENG_4 RELENG_4_8_BP src And then a new branch tag is created with: /usr/src&prompt.root; cvs rtag -b -rRELENG_4_8_BP RELENG_4_8 src The RELENG_* tags are restricted for use by the CVS-meisters and release engineers. A tag is CVS vernacular for a label that identifies the source at a specific point in time. By tagging the tree, we ensure that future release builders will always be able to use the same source we used to create the official FreeBSD Project releases. FreeBSD Development Branch FreeBSD 3.x STABLE Branch FreeBSD 4.x STABLE Branch Bumping up the Version Number Before the final release can be tagged, built, and released, the following files need to be modified to reflect the correct version of FreeBSD: doc/en_US.ISO8859-1/books/handbook/mirrors/chapter.sgml doc/en_US.ISO8859-1/books/porters-handbook/book.sgml doc/share/sgml/freebsd.ent src/Makefile.inc1 src/UPDATING src/gnu/usr.bin/groff/tmac/mdoc.local src/release/Makefile src/release/doc/en_US.ISO8859-1/share/sgml/release.dsl src/release/doc/share/examples/Makefile.relnotesng src/release/doc/share/sgml/release.ent src/share/examples/cvsup/standard-supfile src/sys/conf/newvers.sh src/sys/sys/param.h src/usr.sbin/pkg_install/add/main.c www/en/docs.sgml www/en/cgi/ports.cgi ports/Tools/scripts/release/config The release notes and errata files also need to be adjusted for the new release (on the release branch) and truncated appropriately (on the stable/current branch): src/release/doc/en_US.ISO8859-1/relnotes/common/new.sgml src/release/doc/en_US.ISO8859-1/errata/article.sgml Sysinstall should be updated to note the number of available ports and the amount of disk space required for the Ports Collection. This information is currently kept in src/release/sysinstall/dist.c. After the release has been built, a number of file should be updated to announce the release to the world. www/share/sgml/includes.release.sgml www/share/sgml/includes.release.xsl www/en/releases/* www/en/releng/index.sgml www/en/news/news.xml src/share/misc/bsd-family-tree Creating Release Tags When the final release is ready, the following command will create the RELENG_4_8_0_RELEASE tag. /usr/src&prompt.root; cvs rtag -rRELENG_4_8 RELENG_4_8_0_RELEASE src The Documentation and Ports managers are responsible for tagging the respective trees with the RELEASE_4_8_0 tag. Occasionally, a last minute fix may be required after the final tags have been created. In practice this isn't a problem, since CVS allows tags to be manipulated with cvs tag -d tagname filename. It is very important that any last minute changes be tagged appropriately as part of the release. FreeBSD releases must always be reproduceable. Local hacks in the release engineer's environment are not acceptable. Release Building FreeBSD releases can be built by anyone with a fast machine and access to a source repository. (That should be everyone, since we offer anonymous CVS! See The Handbook for details.) The only special requirement is that the &man.vn.4; device must be available. (On -CURRENT, this device has been replaced by the new &man.md.4; memory disk driver.) If the device is not loaded into your kernel, then the kernel module should be automatically loaded when &man.vnconfig.8; is executed during the boot media creation phase. All of the tools necessary to build a release are available from the CVS repository in src/release. These tools aim to provide a consistent way to build FreeBSD releases. A complete release can actually be built with only a single command, including the creation of ISO images suitable for burning to CDROM, installation floppies, and an FTP install directory. This command is aptly named make release. <command>make release</command> To successfully build a release, you must first populate /usr/obj by running make world or simply make buildworld. The release target requires several variables be set properly to build a release: CHROOTDIR - The directory to be used as the chroot environment for the entire release build. BUILDNAME - The name of the release to be built. CVSROOT - The location of a CVS Repository. RELEASETAG - The CVS tag corresponding to the release you would like to build. If you do not already have access to a local CVS repository, then you may mirror one with CVSup. The supplied supfile, /usr/share/examples/cvsup/cvs-supfile, is a useful starting point for mirroring the CVS repository. If RELEASETAG is omitted, then the release will be built from the HEAD (a.k.a. -CURRENT) branch. Releases built from this branch are normally referred to as -CURRENT snapshots. There are many other variables available to customize the release build. Most of these variables are documented at the top of src/release/Makefile. The exact command used to build the official FreeBSD 4.7 (x86) release was: make release CHROOTDIR=/local3/release \ BUILDNAME=4.7-RELEASE \ CVSROOT=/host/cvs/usr/home/ncvs \ RELEASETAG=RELENG_4_7_0_RELEASE The release Makefile can be broken down into several distinct steps. Creation of a sanitized system environment in a separate directory hierarchy with make installworld. Checkout from CVS of a clean version of the system source, documentation, and ports into the release build hierarchy. Population of /etc and /dev in the chrooted environment. chroot into the release build hierarchy, to make it harder for the outside environment to taint this build. make world in the chrooted environment. Build of Kerberos-related binaries. Build GENERIC kernel. Creation of a staging directory tree where the binary distributions will be built and packaged. Build and installation of the documentation toolchain needed to convert the documentation source (SGML) into HTML and text documents that will accompany the release. Build and installation of the actual documentation (user manuals, tutorials, release notes, hardware compatibility lists, and so on.) Build of the crunched binaries used for installation floppies. Package up distribution tarballs of the binaries and sources. Create the boot media and a fixit floppy. Create FTP installation hierarchy. (optionally) Create ISO images for CDROM/DVD media. For more information about the release build infrastructure, please see &man.release.7;. Building <application>&xfree86;</application> &xfree86; is an important component for many desktop users. Prior to FreeBSD 4.6-RELEASE, releases used &xfree86; 3.X by default. The easiest way to build these versions is to use the src/release/scripts/X11/build_x.sh script. This script requires that &xfree86; and Tcl/Tk already be installed on the build host. After compiling the necessary X servers, the script will package all of the files into tarballs that &man.sysinstall.8; expects to find in the XF86336 directory of the installation media. Beginning with FreeBSD 4.6-RELEASE, &man.sysinstall.8; installs &xfree86; 4.X by default, as a set of normal packages. These can either be the packages generated by the package-building cluster or packages built from an appropriately tagged ports tree. It is important to remove any site-specific settings from /etc/make.conf. For example, it would be unwise to distribute binaries that were built on a system with CPUTYPE set to a specific processor. Contributed Software (<quote>ports</quote>) The FreeBSD Ports collection is a collection of over &os.numports; third-party software packages available for FreeBSD. The &a.portmgr; is responsible for maintaining a consistent ports tree that can be used to create the binary packages that accompany official FreeBSD releases. The release engineering activities for our collection of third-party packages is beyond the scope of this document. A separate article, &art.re.pkgs;, covers this topic in depth. Release ISOs Starting with FreeBSD 4.4, the FreeBSD Project decided to release all four ISO images that were previously sold on the BSDi/Wind River Systems/FreeBSD Mall official CDROM distributions. Each of the four discs must contain a README.TXT file that explains the contents of the disc, a CDROM.INF file that provides meta-data for the disc so that &man.sysinstall.8; can validate and use the contents, and a filename.txt file that provides a manifest for the disc. This manifest can be created with a simple command: /stage/cdrom&prompt.root; find . -type f | sed -e 's/^\.\///' | sort > filename.txt The specific requirements of each CD are outlined below. Disc 1 The first disc is almost completely created by make release. The only changes that should be made to the disc1 directory are the addition of a tools directory, &xfree86;, and as many popular third party software packages as will fit on the disc. The tools directory contains software that allow users to create installation floppies from other operating systems. This disc should be made bootable so that users of modern PCs do not need to create installation floppy disks. If an alternate version of &xfree86; is to be provided, then &man.sysinstall.8; must be updated to reflect the new location and installation instructions. The relevant code is contained in src/release/sysinstall on -STABLE or src/usr.sbin/sysinstall on -CURRENT. Specifically, the files dist.c, menus.c, and config.c will need to be updated. Disc 2 The second disc is also largely created by make release. This disc contains a live filesystem that can be used from &man.sysinstall.8; to troubleshoot a FreeBSD installation. This disc should be bootable and should also contain a compressed copy of the CVS repository in the CVSROOT directory and commercial software demos in the commerce directory. Discs 3 and 4 The remaining two discs contain additional software packages for FreeBSD. The packages should be clustered so that a package and all of its dependencies are included on the same disc. More information about the creation of these discs is provided in the &art.re.pkgs; article. Distribution FTP Sites When the release has been thoroughly tested and packaged for distribution, the master FTP site must be updated. The official FreeBSD public FTP sites are all mirrors of a master server that is open only to other FTP sites. This site is known as ftp-master. When the release is ready, the following files must be modified on ftp-master: /pub/FreeBSD/releases/arch/X.Y-RELEASE/ The installable FTP directory as output from make release. /pub/FreeBSD/ports/arch/packages-X.Y-release/ The complete package build for this release. /pub/FreeBSD/releases/arch/X.Y-RELEASE/tools A symlink to ../../../tools. /pub/FreeBSD/releases/arch/X.Y-RELEASE/packages A symlink to ../../../ports/arch/packages-X.Y-release. /pub/FreeBSD/releases/arch/ISO-IMAGES/X.Y/X.Y-RELEASE-arch-*.iso The ISO images. The * is disc1, disc2, etc. Only if there is a disc1 and there is an alternative first installation CD (for example a stripped-down install with no windowing system) there may be a mini as well. For more information about the distribution mirror architecture of the FreeBSD FTP sites, please see the Mirroring FreeBSD article. It may take many hours to two days after updating ftp-master before a majority of the Tier-1 FTP sites have the new software depending on whether or not a package set got loaded at the same time. It is imperative that the release engineers coordinate with the &a.mirror-announce; before announcing the general availability of new software on the FTP sites. Ideally the release package set should be loaded at least four days prior to release day. The release bits should be loaded between 24 and 48 hours before the planned release time with other file permissions turned off. This will allow the mirror sites to download it but the general public will not be able to download it from the mirror sites. Mail should be sent to &a.mirror-announce; at the time the release bits get posted saying the release has been staged and giving the time that the mirror sites should begin allowing access. Be sure to include a time zone with the time, for example make it relative to GMT. CD-ROM Replication Coming soon: Tips for sending FreeBSD ISOs to a replicator and quality assurance measures to be taken. Extensibility Although FreeBSD forms a complete operating system, there is nothing that forces you to use the system exactly as we have packaged it up for distribution. We have tried to design the system to be as extensible as possible so that it can serve as a platform that other commercial products can be built on top of. The only rule we have about this is that if you are going to distribute FreeBSD with non-trivial changes, we encourage you to document your enhancements! The FreeBSD community can only help support users of the software we provide. We certainly encourage innovation in the form of advanced installation and administration tools, for example, but we can't be expected to answer questions about it. Creating Customized Boot floppies Many sites have complex requirements that may require additional kernel modules or userland tools be added to the installation floppies. The quick and dirty way to accomplish this would be to modify the staging directory of an existing make release build hierarchy: Apply patches or add additional files inside the chroot release build directory. rm ${CHROOTDIR}/usr/obj/usr/src/release/release.[59] rebuild &man.sysinstall.8;, the kernel, or whatever parts of the system your change affected. chroot ${CHROOTDIR} ./mk floppies New release floppies will be located in ${CHROOTDIR}/R/stage/floppies. Alternatively, the boot.flp make target can be called, or the filesystem creating script, src/release/scripts/doFS.sh, may be invoked directly. Local patches may also be supplied to the release build by defining the LOCAL_PATCH variable in make release. Scripting <command>sysinstall</command> The FreeBSD system installation and configuration tool, &man.sysinstall.8;, can be scripted to provide automated installs for large sites. This functionality can be used in conjunction with &intel; PXE[13] to bootstrap systems from the network, or via custom boot floppies with a sysinstall script. An example sysinstall script is available in the CVS tree as src/release/sysinstall/install.cfg. Lessons Learned from FreeBSD 4.4 The release engineering process for 4.4 formally began on August 1st, 2001. After that date all commits to the RELENG_4 branch of FreeBSD had to be explicitly approved by the &a.re;. The first release candidate for the x86 architecture was released on August 16, followed by 4 more release candidates leading up to the final release on September 18th. The security officer was very involved in the last week of the process as several security issues were found in the earlier release candidates. A total of over 500 emails were sent to the &a.re; in little over a month. Our user community has made it very clear that the security and stability of a FreeBSD release should not be sacrificed for any self-imposed deadlines or target release dates. The FreeBSD Project has grown tremendously over its lifetime and the need for standardized release engineering procedures has never been more apparent. This will become even more important as FreeBSD is ported to new platforms. Future Directions It is imperative for our release engineering activities to scale with our growing userbase. Along these lines we are working very hard to document the procedures involved in producing FreeBSD releases. Parallelism - Certain portions of the release build are actually embarrassingly parallel. Most of the tasks are very I/O intensive, so having multiple high-speed disk drives is actually more important than using multiple processors in speeding up the make release process. If multiple disks are used for different hierarchies in the &man.chroot.2; environment, then the CVS checkout of the ports and doc trees can be happening simultaneously as the make world on another disk. Using a RAID solution (hardware or software) can significantly decrease the overall build time. Cross-building releases - Building IA-64 or Alpha release on x86 hardware? make TARGET=ia64 release. Regression Testing - We need better automated correctness testing for FreeBSD. Installation Tools - Our installation program has long since outlived its intended life span. Several projects are under development to provide a more advanced installation mechanism. One of the most promising is the libh project[5] which aims to provide an intelligent new package framework and GUI installation program. Acknowledgements I would like to thank Jordan Hubbard for giving me the opportunity to take on some of the release engineering responsibilities for FreeBSD 4.4 and also for all of his work throughout the years making FreeBSD what it is today. Of course the release wouldn't have been possible without all of the release-related work done by &a.asami;, &a.steve;, &a.bmah;, &a.nik;, &a.obrien;, &a.kris;, &a.jhb; and the rest of the FreeBSD development community. I would also like to thank &a.rgrimes;, &a.phk;, and others who worked on the release engineering tools in the very early days of FreeBSD. This article was influenced by release engineering documents from the CSRG[14], the NetBSD Project[11], and John Baldwin's proposed release engineering process notes[12]. References [1] CVS - Concurrent Versions System [2] CVSup - The CVS-Optimized General Purpose Network File Distribution System [3] [4] FreeBSD Ports Collection [5] The libh Project [6] FreeBSD Committers [7] FreeBSD Core-Team [8] FreeBSD Handbook [9] GNATS: The GNU Bug Tracking System [10] FreeBSD PR Statistics [11] NetBSD Developer Documentation: Release Engineering [12] John Baldwin's FreeBSD Release Engineering Proposal [13] PXE Jumpstart Guide [14] Marshall Kirk McKusick, Michael J. Karels, and Keith Bostic: The Release Engineering of 4.3BSD
diff --git a/en_US.ISO8859-1/books/arch-handbook/scsi/chapter.sgml b/en_US.ISO8859-1/books/arch-handbook/scsi/chapter.sgml index 2c11465429..d5a9ff9ed6 100644 --- a/en_US.ISO8859-1/books/arch-handbook/scsi/chapter.sgml +++ b/en_US.ISO8859-1/books/arch-handbook/scsi/chapter.sgml @@ -1,1983 +1,1983 @@ Common Access Method SCSI Controllers This chapter was written by &a.babkin; Modifications for the handbook made by &a.murray;. Synopsis This document assumes that the reader has a general understanding of device drivers in FreeBSD and of the SCSI protocol. Much of the information in this document was extracted from the drivers: ncr (/sys/pci/ncr.c) by Wolfgang Stanglmeier and Stefan Esser sym (/sys/dev/sym/sym_hipd.c) by Gerard Roudier aic7xxx (/sys/dev/aic7xxx/aic7xxx.c) by Justin T. Gibbs and from the CAM code itself (by Justing T. Gibbs, see /sys/cam/*). When some solution looked the most logical and was essentially verbatim extracted from the code by Justin Gibbs, I marked it as recommended. The document is illustrated with examples in pseudo-code. Although sometimes the examples have many details and look like real code, it is still pseudo-code. It was written to demonstrate the concepts in an understandable way. For a real driver other approaches may be more modular and efficient. It also abstracts from the hardware details, as well as issues that would cloud the demonstrated concepts or that are supposed to be described in the other chapters of the developers handbook. Such details are commonly shown as calls to functions with descriptive names, comments or pseudo-statements. Fortunately real life full-size examples with all the details can be found in the real drivers. General architecture CAM stands for Common Access Method. It is a generic way to address the I/O buses in a SCSI-like way. This allows a separation of the generic device drivers from the drivers controlling the I/O bus: for example the disk driver becomes able to control disks on both SCSI, IDE, and/or any other bus so the disk driver portion does not have to be rewritten (or copied and modified) for every new I/O bus. Thus the two most important active entities are: Peripheral Modules - a driver for peripheral devices (disk, tape, CDROM, etc.) SCSI Interface Modules (SIM) - a Host Bus Adapter drivers for connecting to an I/O bus such as SCSI or IDE. A peripheral driver receives requests from the OS, converts them to a sequence of SCSI commands and passes these SCSI commands to a SCSI Interface Module. The SCSI Interface Module is responsible for passing these commands to the actual hardware (or if the actual hardware is not SCSI but, for example, IDE then also converting the SCSI commands to the native commands of the hardware). Because we are interested in writing a SCSI adapter driver here, from this point on we will consider everything from the SIM standpoint. A typical SIM driver needs to include the following CAM-related header files: #include <cam/cam.h> #include <cam/cam_ccb.h> #include <cam/cam_sim.h> #include <cam/cam_xpt_sim.h> #include <cam/cam_debug.h> #include <cam/scsi/scsi_all.h> The first thing each SIM driver must do is register itself with the CAM subsystem. This is done during the driver's xxx_attach() function (here and further xxx_ is used to denote the unique driver name prefix). The xxx_attach() function itself is called by the system bus auto-configuration code which we do not describe here. This is achieved in multiple steps: first it is necessary to allocate the queue of requests associated with this SIM: struct cam_devq *devq; if(( devq = cam_simq_alloc(SIZE) )==NULL) { error; /* some code to handle the error */ } Here SIZE is the size of the queue to be allocated, maximal number of requests it could contain. It is the number of requests that the SIM driver can handle in parallel on one SCSI card. Commonly it can be calculated as: SIZE = NUMBER_OF_SUPPORTED_TARGETS * MAX_SIMULTANEOUS_COMMANDS_PER_TARGET Next we create a descriptor of our SIM: struct cam_sim *sim; if(( sim = cam_sim_alloc(action_func, poll_func, driver_name, softc, unit, max_dev_transactions, max_tagged_dev_transactions, devq) )==NULL) { cam_simq_free(devq); error; /* some code to handle the error */ } Note that if we are not able to create a SIM descriptor we free the devq also because we can do nothing else with it and we want to conserve memory. If a SCSI card has multiple SCSI buses on it then each bus requires its own cam_sim structure. An interesting question is what to do if a SCSI card has more than one SCSI bus, do we need one devq structure per card or per SCSI bus? The answer given in the comments to the CAM code is: either way, as the driver's author prefers. The arguments are: action_func - pointer to the driver's xxx_action function. - - static void + + static void xxx_action - + struct cam_sim *sim, union ccb *ccb - + poll_func - pointer to the driver's xxx_poll() - - static void + + static void xxx_poll - + struct cam_sim *sim - + driver_name - the name of the actual driver, such as ncr or wds. - softc - pointer to the + softc - pointer to the driver's internal descriptor for this SCSI card. This pointer will be used by the driver in future to get private data. unit - the controller unit number, for example for controller wds0 this number will be 0 max_dev_transactions - maximal number of simultaneous transactions per SCSI target in the non-tagged mode. This value will be almost universally equal to 1, with possible exceptions only for the non-SCSI cards. Also the drivers that hope to take advantage by preparing one transaction while another one is executed may set it to 2 but this does not seem to be worth the complexity. max_tagged_dev_transactions - the same thing, but in the tagged mode. Tags are the SCSI way to initiate multiple transactions on a device: each transaction is assigned a unique tag and the transaction is sent to the device. When the device completes some transaction it sends back the result together with the tag so that the SCSI adapter (and the driver) can tell which transaction was completed. This argument is also known as the maximal tag depth. It depends on the abilities of the SCSI adapter. Finally we register the SCSI buses associated with our SCSI adapter: if(xpt_bus_register(sim, bus_number) != CAM_SUCCESS) { cam_sim_free(sim, /*free_devq*/ TRUE); error; /* some code to handle the error */ } - If there is one devq structure per + If there is one devq structure per SCSI bus (i.e. we consider a card with multiple buses as multiple cards with one bus each) then the bus number will always be 0, otherwise each bus on the SCSI card should be get a distinct number. Each bus needs its own separate structure cam_sim. After that our controller is completely hooked to the CAM - system. The value of devq can be + system. The value of devq can be discarded now: sim will be passed as an argument in all further calls from CAM and devq can be derived from it. CAM provides the framework for such asynchronous events. Some events originate from the lower levels (the SIM drivers), some events originate from the peripheral drivers, some events originate from the CAM subsystem itself. Any driver can register callbacks for some types of the asynchronous events, so that it would be notified if these events occur. A typical example of such an event is a device reset. Each transaction and event identifies the devices to which it applies by the means of path. The target-specific events normally occur during a transaction with this device. So the path from that transaction may be re-used to report this event (this is safe because the event path is copied in the event reporting routine but not deallocated nor passed anywhere further). Also it is safe to allocate paths dynamically at any time including the interrupt routines, although that incurs certain overhead, and a possible problem with this approach is that there may be no free memory at that time. For a bus reset event we need to define a wildcard path including all devices on the bus. So we can create the path for the future bus reset events in advance and avoid problems with the future memory shortage: struct cam_path *path; if(xpt_create_path(&path, /*periph*/NULL, cam_sim_path(sim), CAM_TARGET_WILDCARD, CAM_LUN_WILDCARD) != CAM_REQ_CMP) { xpt_bus_deregister(cam_sim_path(sim)); cam_sim_free(sim, /*free_devq*/TRUE); error; /* some code to handle the error */ } softc->wpath = path; softc->sim = sim; As you can see the path includes: ID of the peripheral driver (NULL here because we have none) ID of the SIM driver (cam_sim_path(sim)) SCSI target number of the device (CAM_TARGET_WILDCARD means all devices) SCSI LUN number of the subdevice (CAM_LUN_WILDCARD means all LUNs) If the driver can not allocate this path it will not be able to work normally, so in that case we dismantle that SCSI bus. And we save the path pointer in the - softc structure for future use. After + softc structure for future use. After that we save the value of sim (or we can also discard it on the exit from xxx_probe() if we wish). That is all for a minimalistic initialization. To do things right there is one more issue left. For a SIM driver there is one particularly interesting event: when a target device is considered lost. In this case resetting the SCSI negotiations with this device may be a good idea. So we register a callback for this event with CAM. The request is passed to CAM by requesting CAM action on a CAM control block for this type of request: struct ccb_setasync csa; xpt_setup_ccb(&csa.ccb_h, path, /*priority*/5); csa.ccb_h.func_code = XPT_SASYNC_CB; csa.event_enable = AC_LOST_DEVICE; csa.callback = xxx_async; csa.callback_arg = sim; xpt_action((union ccb *)&csa); Now we take a look at the xxx_action() and xxx_poll() driver entry points. - - static void + + static void xxx_action - + struct cam_sim *sim, union ccb *ccb - + Do some action on request of the CAM subsystem. Sim describes the SIM for the request, CCB is the request itself. CCB stands for CAM Control Block. It is a union of many specific instances, each describing arguments for some type of transactions. All of these instances share the CCB header where the common part of arguments is stored. CAM supports the SCSI controllers working in both initiator (normal) mode and target (simulating a SCSI device) mode. Here we only consider the part relevant to the initiator mode. There are a few function and macros (in other words, methods) defined to access the public data in the struct sim: cam_sim_path(sim) - the path ID (see above) cam_sim_name(sim) - the name of the sim cam_sim_softc(sim) - the pointer to the softc (driver private data) structure cam_sim_unit(sim) - the unit number cam_sim_bus(sim) - the bus ID To identify the device, xxx_action() can get the unit number and pointer to its structure softc using these functions. The type of request is stored in - ccb->ccb_h.func_code. So generally + ccb->ccb_h.func_code. So generally xxx_action() consists of a big switch: struct xxx_softc *softc = (struct xxx_softc *) cam_sim_softc(sim); struct ccb_hdr *ccb_h = &ccb->ccb_h; int unit = cam_sim_unit(sim); int bus = cam_sim_bus(sim); switch(ccb_h->func_code) { case ...: ... default: ccb_h->status = CAM_REQ_INVALID; xpt_done(ccb); break; } As can be seen from the default case (if an unknown command was received) the return code of the command is set into - ccb->ccb_h.status and the completed + ccb->ccb_h.status and the completed CCB is returned back to CAM by calling xpt_done(ccb). xpt_done() does not have to be called from xxx_action(): For example an I/O request may be enqueued inside the SIM driver and/or its SCSI controller. Then when the device would post an interrupt signaling that the processing of this request is complete xpt_done() may be called from the interrupt handling routine. Actually, the CCB status is not only assigned as a return code but a CCB has some status all the time. Before CCB is passed to the xxx_action() routine it gets the status CCB_REQ_INPROG meaning that it is in progress. There are a surprising number of status values defined in /sys/cam/cam.h which should be able to represent the status of a request in great detail. More interesting yet, the status is in fact a bitwise or of an enumerated status value (the lower 6 bits) and possible additional flag-like bits (the upper bits). The enumerated values will be discussed later in more detail. The summary of them can be found in the Errors Summary section. The possible status flags are: CAM_DEV_QFRZN - if the SIM driver gets a serious error (for example, the device does not respond to the selection or breaks the SCSI protocol) when processing a CCB it should freeze the request queue by calling xpt_freeze_simq(), return the other enqueued but not processed yet CCBs for this device back to the CAM queue, then set this flag for the troublesome CCB and call xpt_done(). This flag causes the CAM subsystem to unfreeze the queue after it handles the error. CAM_AUTOSNS_VALID - if the device returned an error condition and the flag CAM_DIS_AUTOSENSE is not set in CCB the SIM driver must execute the REQUEST SENSE command automatically to extract the sense (extended error information) data from the device. If this attempt was successful the sense data should be saved in the CCB and this flag set. CAM_RELEASE_SIMQ - like CAM_DEV_QFRZN but used in case there is some problem (or resource shortage) with the SCSI controller itself. Then all the future requests to the controller should be stopped by xpt_freeze_simq(). The controller queue will be restarted after the SIM driver overcomes the shortage and informs CAM by returning some CCB with this flag set. CAM_SIM_QUEUED - when SIM puts a CCB into its request queue this flag should be set (and removed when this CCB gets dequeued before being returned back to CAM). This flag is not used anywhere in the CAM code now, so its purpose is purely diagnostic. The function xxx_action() is not allowed to sleep, so all the synchronization for resource access must be done using SIM or device queue freezing. Besides the aforementioned flags the CAM subsystem provides functions xpt_release_simq() and xpt_release_devq() to unfreeze the queues directly, without passing a CCB to CAM. The CCB header contains the following fields: path - path ID for the request target_id - target device ID for the request target_lun - LUN ID of the target device timeout - timeout interval for this command, in milliseconds timeout_ch - a convenience place for the SIM driver to store the timeout handle (the CAM subsystem itself does not make any assumptions about it) flags - various bits of information about the request spriv_ptr0, spriv_ptr1 - fields reserved for private use by the SIM driver (such as linking to the SIM queues or SIM private control blocks); actually, they exist as unions: spriv_ptr0 and spriv_ptr1 have the type (void *), spriv_field0 and spriv_field1 have the type unsigned long, sim_priv.entries[0].bytes and sim_priv.entries[1].bytes are byte arrays of the size consistent with the other incarnations of the union and sim_priv.bytes is one array, twice bigger. The recommended way of using the SIM private fields of CCB is to define some meaningful names for them and use these meaningful names in the driver, like: #define ccb_some_meaningful_name sim_priv.entries[0].bytes #define ccb_hcb spriv_ptr1 /* for hardware control block */ The most common initiator mode requests are: XPT_SCSI_IO - execute an I/O transaction The instance struct ccb_scsiio csio of the union ccb is used to transfer the arguments. They are: cdb_io - pointer to the SCSI command buffer or the buffer itself cdb_len - SCSI command length data_ptr - pointer to the data buffer (gets a bit complicated if scatter/gather is used) dxfer_len - length of the data to transfer sglist_cnt - counter of the scatter/gather segments scsi_status - place to return the SCSI status sense_data - buffer for the SCSI sense information if the command returns an error (the SIM driver is supposed to run the REQUEST SENSE command automatically in this case if the CCB flag CAM_DIS_AUTOSENSE is not set) sense_len - the length of that buffer (if it happens to be higher than size of sense_data the SIM driver must silently assume the smaller value) resid, sense_resid - if the transfer of data or SCSI sense returned an error these are the returned counters of the residual (not transferred) data. They do not seem to be especially meaningful, so in a case when they are difficult to compute (say, counting bytes in the SCSI controller's FIFO buffer) an approximate value will do as well. For a successfully completed transfer they must be set to zero. tag_action - the kind of tag to use: CAM_TAG_ACTION_NONE - do not use tags for this transaction MSG_SIMPLE_Q_TAG, MSG_HEAD_OF_Q_TAG, MSG_ORDERED_Q_TAG - value equal to the appropriate tag message (see /sys/cam/scsi/scsi_message.h); this gives only the tag type, the SIM driver must assign the tag value itself The general logic of handling this request is the following: The first thing to do is to check for possible races, to make sure that the command did not get aborted when it was sitting in the queue: struct ccb_scsiio *csio = &ccb->csio; if ((ccb_h->status & CAM_STATUS_MASK) != CAM_REQ_INPROG) { xpt_done(ccb); return; } Also we check that the device is supported at all by our controller: if(ccb_h->target_id > OUR_MAX_SUPPORTED_TARGET_ID || cch_h->target_id == OUR_SCSI_CONTROLLERS_OWN_ID) { ccb_h->status = CAM_TID_INVALID; xpt_done(ccb); return; } if(ccb_h->target_lun > OUR_MAX_SUPPORTED_LUN) { ccb_h->status = CAM_LUN_INVALID; xpt_done(ccb); return; } Then allocate whatever data structures (such as card-dependent hardware control block) we need to process this request. If we ca not then freeze the SIM queue and remember that we have a pending operation, return the CCB back and ask CAM to re-queue it. Later when the resources become available the SIM queue must be unfrozen by returning a ccb with the CAM_SIMQ_RELEASE bit set in its status. Otherwise, if all went well, link the CCB with the hardware control block (HCB) and mark it as queued. struct xxx_hcb *hcb = allocate_hcb(softc, unit, bus); if(hcb == NULL) { softc->flags |= RESOURCE_SHORTAGE; xpt_freeze_simq(sim, /*count*/1); ccb_h->status = CAM_REQUEUE_REQ; xpt_done(ccb); return; } hcb->ccb = ccb; ccb_h->ccb_hcb = (void *)hcb; ccb_h->status |= CAM_SIM_QUEUED; Extract the target data from CCB into the hardware control block. Check if we are asked to assign a tag and if yes then generate an unique tag and build the SCSI tag messages. The SIM driver is also responsible for negotiations with the devices to set the maximal mutually supported bus width, synchronous rate and offset. hcb->target = ccb_h->target_id; hcb->lun = ccb_h->target_lun; generate_identify_message(hcb); if( ccb_h->tag_action != CAM_TAG_ACTION_NONE ) generate_unique_tag_message(hcb, ccb_h->tag_action); if( !target_negotiated(hcb) ) generate_negotiation_messages(hcb); Then set up the SCSI command. The command storage may be specified in the CCB in many interesting ways, specified by the CCB flags. The command buffer can be contained in CCB or pointed to, in the latter case the pointer may be physical or virtual. Since the hardware commonly needs physical address we always convert the address to the physical one. A NOT-QUITE RELATED NOTE: Normally this is done by a call to vtophys(), but for the PCI device (which account for most of the SCSI controllers now) drivers' portability to the Alpha architecture the conversion must be done by vtobus() instead due to special Alpha quirks. [IMHO it would be much better to have two separate functions, vtop() and ptobus() then vtobus() would be a simple superposition of them.] In case if a physical address is requested it is OK to return the CCB with the status CAM_REQ_INVALID, the current drivers do that. But it is also possible to compile the Alpha-specific piece of code, as in this example (there should be a more direct way to do that, without conditional compilation in the drivers). If necessary a physical address can be also converted or mapped back to a virtual address but with big pain, so we do not do that. if(ccb_h->flags & CAM_CDB_POINTER) { /* CDB is a pointer */ if(!(ccb_h->flags & CAM_CDB_PHYS)) { /* CDB pointer is virtual */ hcb->cmd = vtobus(csio->cdb_io.cdb_ptr); } else { /* CDB pointer is physical */ #if defined(__alpha__) hcb->cmd = csio->cdb_io.cdb_ptr | alpha_XXX_dmamap_or ; #else hcb->cmd = csio->cdb_io.cdb_ptr ; #endif } } else { /* CDB is in the ccb (buffer) */ hcb->cmd = vtobus(csio->cdb_io.cdb_bytes); } hcb->cmdlen = csio->cdb_len; Now it is time to set up the data. Again, the data storage may be specified in the CCB in many interesting ways, specified by the CCB flags. First we get the direction of the data transfer. The simplest case is if there is no data to transfer: int dir = (ccb_h->flags & CAM_DIR_MASK); if (dir == CAM_DIR_NONE) goto end_data; Then we check if the data is in one chunk or in a scatter-gather list, and the addresses are physical or virtual. The SCSI controller may be able to handle only a limited number of chunks of limited length. If the request hits this limitation we return an error. We use a special function to return the CCB to handle in one place the HCB resource shortages. The functions to add chunks are driver-dependent, and here we leave them without detailed implementation. See description of the SCSI command (CDB) handling for the details on the address-translation issues. If some variation is too difficult or impossible to implement with a particular card it is OK to return the status CAM_REQ_INVALID. Actually, it seems like the scatter-gather ability is not used anywhere in the CAM code now. But at least the case for a single non-scattered virtual buffer must be implemented, it is actively used by CAM. int rv; initialize_hcb_for_data(hcb); if((!(ccb_h->flags & CAM_SCATTER_VALID)) { /* single buffer */ if(!(ccb_h->flags & CAM_DATA_PHYS)) { rv = add_virtual_chunk(hcb, csio->data_ptr, csio->dxfer_len, dir); } } else { rv = add_physical_chunk(hcb, csio->data_ptr, csio->dxfer_len, dir); } } else { int i; struct bus_dma_segment *segs; segs = (struct bus_dma_segment *)csio->data_ptr; if ((ccb_h->flags & CAM_SG_LIST_PHYS) != 0) { /* The SG list pointer is physical */ rv = setup_hcb_for_physical_sg_list(hcb, segs, csio->sglist_cnt); } else if (!(ccb_h->flags & CAM_DATA_PHYS)) { /* SG buffer pointers are virtual */ for (i = 0; i < csio->sglist_cnt; i++) { rv = add_virtual_chunk(hcb, segs[i].ds_addr, segs[i].ds_len, dir); if (rv != CAM_REQ_CMP) break; } } else { /* SG buffer pointers are physical */ for (i = 0; i < csio->sglist_cnt; i++) { rv = add_physical_chunk(hcb, segs[i].ds_addr, segs[i].ds_len, dir); if (rv != CAM_REQ_CMP) break; } } } if(rv != CAM_REQ_CMP) { /* we expect that add_*_chunk() functions return CAM_REQ_CMP * if they added a chunk successfully, CAM_REQ_TOO_BIG if * the request is too big (too many bytes or too many chunks), * CAM_REQ_INVALID in case of other troubles */ free_hcb_and_ccb_done(hcb, ccb, rv); return; } end_data: If disconnection is disabled for this CCB we pass this information to the hcb: if(ccb_h->flags & CAM_DIS_DISCONNECT) hcb_disable_disconnect(hcb); If the controller is able to run REQUEST SENSE command all by itself then the value of the flag CAM_DIS_AUTOSENSE should also be passed to it, to prevent automatic REQUEST SENSE if the CAM subsystem does not want it. The only thing left is to set up the timeout, pass our hcb to the hardware and return, the rest will be done by the interrupt handler (or timeout handler). ccb_h->timeout_ch = timeout(xxx_timeout, (caddr_t) hcb, (ccb_h->timeout * hz) / 1000); /* convert milliseconds to ticks */ put_hcb_into_hardware_queue(hcb); return; And here is a possible implementation of the function returning CCB: static void free_hcb_and_ccb_done(struct xxx_hcb *hcb, union ccb *ccb, u_int32_t status) { struct xxx_softc *softc = hcb->softc; ccb->ccb_h.ccb_hcb = 0; if(hcb != NULL) { untimeout(xxx_timeout, (caddr_t) hcb, ccb->ccb_h.timeout_ch); /* we're about to free a hcb, so the shortage has ended */ if(softc->flags & RESOURCE_SHORTAGE) { softc->flags &= ~RESOURCE_SHORTAGE; status |= CAM_RELEASE_SIMQ; } free_hcb(hcb); /* also removes hcb from any internal lists */ } ccb->ccb_h.status = status | (ccb->ccb_h.status & ~(CAM_STATUS_MASK|CAM_SIM_QUEUED)); xpt_done(ccb); } XPT_RESET_DEV - send the SCSI BUS DEVICE RESET message to a device There is no data transferred in CCB except the header and the most interesting argument of it is target_id. Depending on the controller hardware a hardware control block just like for the XPT_SCSI_IO request may be constructed (see XPT_SCSI_IO request description) and sent to the controller or the SCSI controller may be immediately programmed to send this RESET message to the device or this request may be just not supported (and return the status CAM_REQ_INVALID). Also on completion of the request all the disconnected transactions for this target must be aborted (probably in the interrupt routine). Also all the current negotiations for the target are lost on reset, so they might be cleaned too. Or they clearing may be deferred, because anyway the target would request re-negotiation on the next transaction. XPT_RESET_BUS - send the RESET signal to the SCSI bus No arguments are passed in the CCB, the only interesting argument is the SCSI bus indicated by the struct sim pointer. A minimalistic implementation would forget the SCSI negotiations for all the devices on the bus and return the status CAM_REQ_CMP. The proper implementation would in addition actually reset the SCSI bus (possible also reset the SCSI controller) and mark all the CCBs being processed, both those in the hardware queue and those being disconnected, as done with the status CAM_SCSI_BUS_RESET. Like: int targ, lun; struct xxx_hcb *h, *hh; struct ccb_trans_settings neg; struct cam_path *path; /* The SCSI bus reset may take a long time, in this case its completion * should be checked by interrupt or timeout. But for simplicity * we assume here that it is really fast. */ reset_scsi_bus(softc); /* drop all enqueued CCBs */ for(h = softc->first_queued_hcb; h != NULL; h = hh) { hh = h->next; free_hcb_and_ccb_done(h, h->ccb, CAM_SCSI_BUS_RESET); } /* the clean values of negotiations to report */ neg.bus_width = 8; neg.sync_period = neg.sync_offset = 0; neg.valid = (CCB_TRANS_BUS_WIDTH_VALID | CCB_TRANS_SYNC_RATE_VALID | CCB_TRANS_SYNC_OFFSET_VALID); /* drop all disconnected CCBs and clean negotiations */ for(targ=0; targ <= OUR_MAX_SUPPORTED_TARGET; targ++) { clean_negotiations(softc, targ); /* report the event if possible */ if(xpt_create_path(&path, /*periph*/NULL, cam_sim_path(sim), targ, CAM_LUN_WILDCARD) == CAM_REQ_CMP) { xpt_async(AC_TRANSFER_NEG, path, &neg); xpt_free_path(path); } for(lun=0; lun <= OUR_MAX_SUPPORTED_LUN; lun++) for(h = softc->first_discon_hcb[targ][lun]; h != NULL; h = hh) { hh=h->next; free_hcb_and_ccb_done(h, h->ccb, CAM_SCSI_BUS_RESET); } } ccb->ccb_h.status = CAM_REQ_CMP; xpt_done(ccb); /* report the event */ xpt_async(AC_BUS_RESET, softc->wpath, NULL); return; Implementing the SCSI bus reset as a function may be a good idea because it would be re-used by the timeout function as a last resort if the things go wrong. XPT_ABORT - abort the specified CCB The arguments are transferred in the instance struct ccb_abort cab of the union ccb. The only argument field in it is: abort_ccb - pointer to the CCB to be aborted If the abort is not supported just return the status CAM_UA_ABORT. This is also the easy way to minimally implement this call, return CAM_UA_ABORT in any case. The hard way is to implement this request honestly. First check that abort applies to a SCSI transaction: struct ccb *abort_ccb; abort_ccb = ccb->cab.abort_ccb; if(abort_ccb->ccb_h.func_code != XPT_SCSI_IO) { ccb->ccb_h.status = CAM_UA_ABORT; xpt_done(ccb); return; } Then it is necessary to find this CCB in our queue. This can be done by walking the list of all our hardware control blocks in search for one associated with this CCB: struct xxx_hcb *hcb, *h; hcb = NULL; /* We assume that softc->first_hcb is the head of the list of all * HCBs associated with this bus, including those enqueued for * processing, being processed by hardware and disconnected ones. */ for(h = softc->first_hcb; h != NULL; h = h->next) { if(h->ccb == abort_ccb) { hcb = h; break; } } if(hcb == NULL) { /* no such CCB in our queue */ ccb->ccb_h.status = CAM_PATH_INVALID; xpt_done(ccb); return; } hcb=found_hcb; Now we look at the current processing status of the HCB. It may be either sitting in the queue waiting to be sent to the SCSI bus, being transferred right now, or disconnected and waiting for the result of the command, or actually completed by hardware but not yet marked as done by software. To make sure that we do not get in any races with hardware we mark the HCB as being aborted, so that if this HCB is about to be sent to the SCSI bus the SCSI controller will see this flag and skip it. int hstatus; /* shown as a function, in case special action is needed to make * this flag visible to hardware */ set_hcb_flags(hcb, HCB_BEING_ABORTED); abort_again: hstatus = get_hcb_status(hcb); switch(hstatus) { case HCB_SITTING_IN_QUEUE: remove_hcb_from_hardware_queue(hcb); /* FALLTHROUGH */ case HCB_COMPLETED: /* this is an easy case */ free_hcb_and_ccb_done(hcb, abort_ccb, CAM_REQ_ABORTED); break; If the CCB is being transferred right now we would like to signal to the SCSI controller in some hardware-dependent way that we want to abort the current transfer. The SCSI controller would set the SCSI ATTENTION signal and when the target responds to it send an ABORT message. We also reset the timeout to make sure that the target is not sleeping forever. If the command would not get aborted in some reasonable time like 10 seconds the timeout routine would go ahead and reset the whole SCSI bus. Because the command will be aborted in some reasonable time we can just return the abort request now as successfully completed, and mark the aborted CCB as aborted (but not mark it as done yet). case HCB_BEING_TRANSFERRED: untimeout(xxx_timeout, (caddr_t) hcb, abort_ccb->ccb_h.timeout_ch); abort_ccb->ccb_h.timeout_ch = timeout(xxx_timeout, (caddr_t) hcb, 10 * hz); abort_ccb->ccb_h.status = CAM_REQ_ABORTED; /* ask the controller to abort that HCB, then generate * an interrupt and stop */ if(signal_hardware_to_abort_hcb_and_stop(hcb) < 0) { /* oops, we missed the race with hardware, this transaction * got off the bus before we aborted it, try again */ goto abort_again; } break; If the CCB is in the list of disconnected then set it up as an abort request and re-queue it at the front of hardware queue. Reset the timeout and report the abort request to be completed. case HCB_DISCONNECTED: untimeout(xxx_timeout, (caddr_t) hcb, abort_ccb->ccb_h.timeout_ch); abort_ccb->ccb_h.timeout_ch = timeout(xxx_timeout, (caddr_t) hcb, 10 * hz); put_abort_message_into_hcb(hcb); put_hcb_at_the_front_of_hardware_queue(hcb); break; } ccb->ccb_h.status = CAM_REQ_CMP; xpt_done(ccb); return; That is all for the ABORT request, although there is one more issue. Because the ABORT message cleans all the ongoing transactions on a LUN we have to mark all the other active transactions on this LUN as aborted. That should be done in the interrupt routine, after the transaction gets aborted. Implementing the CCB abort as a function may be quite a good idea, this function can be re-used if an I/O transaction times out. The only difference would be that the timed out transaction would return the status CAM_CMD_TIMEOUT for the timed out request. Then the case XPT_ABORT would be small, like that: case XPT_ABORT: struct ccb *abort_ccb; abort_ccb = ccb->cab.abort_ccb; if(abort_ccb->ccb_h.func_code != XPT_SCSI_IO) { ccb->ccb_h.status = CAM_UA_ABORT; xpt_done(ccb); return; } if(xxx_abort_ccb(abort_ccb, CAM_REQ_ABORTED) < 0) /* no such CCB in our queue */ ccb->ccb_h.status = CAM_PATH_INVALID; else ccb->ccb_h.status = CAM_REQ_CMP; xpt_done(ccb); return; XPT_SET_TRAN_SETTINGS - explicitly set values of SCSI transfer settings The arguments are transferred in the instance struct ccb_trans_setting cts of the union ccb: valid - a bitmask showing which settings should be updated: CCB_TRANS_SYNC_RATE_VALID - synchronous transfer rate CCB_TRANS_SYNC_OFFSET_VALID - synchronous offset CCB_TRANS_BUS_WIDTH_VALID - bus width CCB_TRANS_DISC_VALID - set enable/disable disconnection CCB_TRANS_TQ_VALID - set enable/disable tagged queuing flags - consists of two parts, binary arguments and identification of sub-operations. The binary arguments are: CCB_TRANS_DISC_ENB - enable disconnection CCB_TRANS_TAG_ENB - enable tagged queuing the sub-operations are: CCB_TRANS_CURRENT_SETTINGS - change the current negotiations CCB_TRANS_USER_SETTINGS - remember the desired user values sync_period, sync_offset - self-explanatory, if sync_offset==0 then the asynchronous mode is requested bus_width - bus width, in bits (not bytes) Two sets of negotiated parameters are supported, the user settings and the current settings. The user settings are not really used much in the SIM drivers, this is mostly just a piece of memory where the upper levels can store (and later recall) its ideas about the parameters. Setting the user parameters does not cause re-negotiation of the transfer rates. But when the SCSI controller does a negotiation it must never set the values higher than the user parameters, so it is essentially the top boundary. The current settings are, as the name says, current. Changing them means that the parameters must be re-negotiated on the next transfer. Again, these new current settings are not supposed to be forced on the device, just they are used as the initial step of negotiations. Also they must be limited by actual capabilities of the SCSI controller: for example, if the SCSI controller has 8-bit bus and the request asks to set 16-bit wide transfers this parameter must be silently truncated to 8-bit transfers before sending it to the device. One caveat is that the bus width and synchronous parameters are per target while the disconnection and tag enabling parameters are per lun. The recommended implementation is to keep 3 sets of negotiated (bus width and synchronous transfer) parameters: user - the user set, as above current - those actually in effect goal - those requested by setting of the current parameters The code looks like: struct ccb_trans_settings *cts; int targ, lun; int flags; cts = &ccb->cts; targ = ccb_h->target_id; lun = ccb_h->target_lun; flags = cts->flags; if(flags & CCB_TRANS_USER_SETTINGS) { if(flags & CCB_TRANS_SYNC_RATE_VALID) softc->user_sync_period[targ] = cts->sync_period; if(flags & CCB_TRANS_SYNC_OFFSET_VALID) softc->user_sync_offset[targ] = cts->sync_offset; if(flags & CCB_TRANS_BUS_WIDTH_VALID) softc->user_bus_width[targ] = cts->bus_width; if(flags & CCB_TRANS_DISC_VALID) { softc->user_tflags[targ][lun] &= ~CCB_TRANS_DISC_ENB; softc->user_tflags[targ][lun] |= flags & CCB_TRANS_DISC_ENB; } if(flags & CCB_TRANS_TQ_VALID) { softc->user_tflags[targ][lun] &= ~CCB_TRANS_TQ_ENB; softc->user_tflags[targ][lun] |= flags & CCB_TRANS_TQ_ENB; } } if(flags & CCB_TRANS_CURRENT_SETTINGS) { if(flags & CCB_TRANS_SYNC_RATE_VALID) softc->goal_sync_period[targ] = max(cts->sync_period, OUR_MIN_SUPPORTED_PERIOD); if(flags & CCB_TRANS_SYNC_OFFSET_VALID) softc->goal_sync_offset[targ] = min(cts->sync_offset, OUR_MAX_SUPPORTED_OFFSET); if(flags & CCB_TRANS_BUS_WIDTH_VALID) softc->goal_bus_width[targ] = min(cts->bus_width, OUR_BUS_WIDTH); if(flags & CCB_TRANS_DISC_VALID) { softc->current_tflags[targ][lun] &= ~CCB_TRANS_DISC_ENB; softc->current_tflags[targ][lun] |= flags & CCB_TRANS_DISC_ENB; } if(flags & CCB_TRANS_TQ_VALID) { softc->current_tflags[targ][lun] &= ~CCB_TRANS_TQ_ENB; softc->current_tflags[targ][lun] |= flags & CCB_TRANS_TQ_ENB; } } ccb->ccb_h.status = CAM_REQ_CMP; xpt_done(ccb); return; Then when the next I/O request will be processed it will check if it has to re-negotiate, for example by calling the function target_negotiated(hcb). It can be implemented like this: int target_negotiated(struct xxx_hcb *hcb) { struct softc *softc = hcb->softc; int targ = hcb->targ; if( softc->current_sync_period[targ] != softc->goal_sync_period[targ] || softc->current_sync_offset[targ] != softc->goal_sync_offset[targ] || softc->current_bus_width[targ] != softc->goal_bus_width[targ] ) return 0; /* FALSE */ else return 1; /* TRUE */ } After the values are re-negotiated the resulting values must be assigned to both current and goal parameters, so for future I/O transactions the current and goal parameters would be the same and target_negotiated() would return TRUE. When the card is initialized (in xxx_attach()) the current negotiation values must be initialized to narrow asynchronous mode, the goal and current values must be initialized to the maximal values supported by controller. XPT_GET_TRAN_SETTINGS - get values of SCSI transfer settings This operations is the reverse of XPT_SET_TRAN_SETTINGS. Fill up the CCB instance struct ccb_trans_setting cts with data as requested by the flags CCB_TRANS_CURRENT_SETTINGS or CCB_TRANS_USER_SETTINGS (if both are set then the existing drivers return the current settings). Set all the bits in the valid field. XPT_CALC_GEOMETRY - calculate logical (BIOS) geometry of the disk The arguments are transferred in the instance struct ccb_calc_geometry ccg of the union ccb: block_size - input, block (A.K.A sector) size in bytes volume_size - input, volume size in bytes cylinders - output, logical cylinders heads - output, logical heads secs_per_track - output, logical sectors per track If the returned geometry differs much enough from what the SCSI controller BIOS thinks and a disk on this SCSI controller is used as bootable the system may not be able to boot. The typical calculation example taken from the aic7xxx driver is: struct ccb_calc_geometry *ccg; u_int32_t size_mb; u_int32_t secs_per_cylinder; int extended; ccg = &ccb->ccg; size_mb = ccg->volume_size / ((1024L * 1024L) / ccg->block_size); extended = check_cards_EEPROM_for_extended_geometry(softc); if (size_mb > 1024 && extended) { ccg->heads = 255; ccg->secs_per_track = 63; } else { ccg->heads = 64; ccg->secs_per_track = 32; } secs_per_cylinder = ccg->heads * ccg->secs_per_track; ccg->cylinders = ccg->volume_size / secs_per_cylinder; ccb->ccb_h.status = CAM_REQ_CMP; xpt_done(ccb); return; This gives the general idea, the exact calculation depends on the quirks of the particular BIOS. If BIOS provides no way set the extended translation flag in EEPROM this flag should normally be assumed equal to 1. Other popular geometries are: 128 heads, 63 sectors - Symbios controllers 16 heads, 63 sectors - old controllers Some system BIOSes and SCSI BIOSes fight with each other with variable success, for example a combination of Symbios 875/895 SCSI and Phoenix BIOS can give geometry 128/63 after power up and 255/63 after a hard reset or soft reboot. XPT_PATH_INQ - path inquiry, in other words get the SIM driver and SCSI controller (also known as HBA - Host Bus Adapter) properties The properties are returned in the instance struct ccb_pathinq cpi of the union ccb: version_num - the SIM driver version number, now all drivers use 1 hba_inquiry - bitmask of features supported by the controller: PI_MDP_ABLE - supports MDP message (something from SCSI3?) PI_WIDE_32 - supports 32 bit wide SCSI PI_WIDE_16 - supports 16 bit wide SCSI PI_SDTR_ABLE - can negotiate synchronous transfer rate PI_LINKED_CDB - supports linked commands PI_TAG_ABLE - supports tagged commands PI_SOFT_RST - supports soft reset alternative (hard reset and soft reset are mutually exclusive within a SCSI bus) target_sprt - flags for target mode support, 0 if unsupported hba_misc - miscellaneous controller features: PIM_SCANHILO - bus scans from high ID to low ID PIM_NOREMOVE - removable devices not included in scan PIM_NOINITIATOR - initiator role not supported PIM_NOBUSRESET - user has disabled initial BUS RESET hba_eng_cnt - mysterious HBA engine count, something related to compression, now is always set to 0 vuhba_flags - vendor-unique flags, unused now max_target - maximal supported target ID (7 for 8-bit bus, 15 for 16-bit bus, 127 for Fibre Channel) max_lun - maximal supported LUN ID (7 for older SCSI controllers, 63 for newer ones) async_flags - bitmask of installed Async handler, unused now hpath_id - highest Path ID in the subsystem, unused now unit_number - the controller unit number, cam_sim_unit(sim) bus_id - the bus number, cam_sim_bus(sim) initiator_id - the SCSI ID of the controller itself base_transfer_speed - nominal transfer speed in KB/s for asynchronous narrow transfers, equals to 3300 for SCSI sim_vid - SIM driver's vendor id, a zero-terminated string of maximal length SIM_IDLEN including the terminating zero hba_vid - SCSI controller's vendor id, a zero-terminated string of maximal length HBA_IDLEN including the terminating zero dev_name - device driver name, a zero-terminated string of maximal length DEV_IDLEN including the terminating zero, equal to cam_sim_name(sim) The recommended way of setting the string fields is using strncpy, like: strncpy(cpi->dev_name, cam_sim_name(sim), DEV_IDLEN); After setting the values set the status to CAM_REQ_CMP and mark the CCB as done. Polling - - static void + + static void xxx_poll - + struct cam_sim *sim - + The poll function is used to simulate the interrupts when the interrupt subsystem is not functioning (for example, when the system has crashed and is creating the system dump). The CAM subsystem sets the proper interrupt level before calling the poll routine. So all it needs to do is to call the interrupt routine (or the other way around, the poll routine may be doing the real action and the interrupt routine would just call the poll routine). Why bother about a separate function then? Because of different calling conventions. The xxx_poll routine gets the struct cam_sim pointer as its argument when the PCI interrupt routine by common convention gets pointer to the struct - xxx_softc and the ISA interrupt routine + xxx_softc and the ISA interrupt routine gets just the device unit number. So the poll routine would normally look as: static void xxx_poll(struct cam_sim *sim) { xxx_intr((struct xxx_softc *)cam_sim_softc(sim)); /* for PCI device */ } or static void xxx_poll(struct cam_sim *sim) { xxx_intr(cam_sim_unit(sim)); /* for ISA device */ } Asynchronous Events If an asynchronous event callback has been set up then the callback function should be defined. static void ahc_async(void *callback_arg, u_int32_t code, struct cam_path *path, void *arg) callback_arg - the value supplied when registering the callback code - identifies the type of event path - identifies the devices to which the event applies arg - event-specific argument Implementation for a single type of event, AC_LOST_DEVICE, looks like: struct xxx_softc *softc; struct cam_sim *sim; int targ; struct ccb_trans_settings neg; sim = (struct cam_sim *)callback_arg; softc = (struct xxx_softc *)cam_sim_softc(sim); switch (code) { case AC_LOST_DEVICE: targ = xpt_path_target_id(path); if(targ <= OUR_MAX_SUPPORTED_TARGET) { clean_negotiations(softc, targ); /* send indication to CAM */ neg.bus_width = 8; neg.sync_period = neg.sync_offset = 0; neg.valid = (CCB_TRANS_BUS_WIDTH_VALID | CCB_TRANS_SYNC_RATE_VALID | CCB_TRANS_SYNC_OFFSET_VALID); xpt_async(AC_TRANSFER_NEG, path, &neg); } break; default: break; } Interrupts The exact type of the interrupt routine depends on the type of the peripheral bus (PCI, ISA and so on) to which the SCSI controller is connected. The interrupt routines of the SIM drivers run at the interrupt level splcam. So splcam() should be used in the driver to synchronize activity between the interrupt routine and the rest of the driver (for a multiprocessor-aware driver things get yet more interesting but we ignore this case here). The pseudo-code in this document happily ignores the problems of synchronization. The real code must not ignore them. A simple-minded approach is to set splcam() on the entry to the other routines and reset it on return thus protecting them by one big critical section. To make sure that the interrupt level will be always restored a wrapper function can be defined, like: static void xxx_action(struct cam_sim *sim, union ccb *ccb) { int s; s = splcam(); xxx_action1(sim, ccb); splx(s); } static void xxx_action1(struct cam_sim *sim, union ccb *ccb) { ... process the request ... } This approach is simple and robust but the problem with it is that interrupts may get blocked for a relatively long time and this would negatively affect the system's performance. On the other hand the functions of the spl() family have rather high overhead, so vast amount of tiny critical sections may not be good either. The conditions handled by the interrupt routine and the details depend very much on the hardware. We consider the set of typical conditions. First, we check if a SCSI reset was encountered on the bus (probably caused by another SCSI controller on the same SCSI bus). If so we drop all the enqueued and disconnected requests, report the events and re-initialize our SCSI controller. It is important that during this initialization the controller will not issue another reset or else two controllers on the same SCSI bus could ping-pong resets forever. The case of fatal controller error/hang could be handled in the same place, but it will probably need also sending RESET signal to the SCSI bus to reset the status of the connections with the SCSI devices. int fatal=0; struct ccb_trans_settings neg; struct cam_path *path; if( detected_scsi_reset(softc) || (fatal = detected_fatal_controller_error(softc)) ) { int targ, lun; struct xxx_hcb *h, *hh; /* drop all enqueued CCBs */ for(h = softc->first_queued_hcb; h != NULL; h = hh) { hh = h->next; free_hcb_and_ccb_done(h, h->ccb, CAM_SCSI_BUS_RESET); } /* the clean values of negotiations to report */ neg.bus_width = 8; neg.sync_period = neg.sync_offset = 0; neg.valid = (CCB_TRANS_BUS_WIDTH_VALID | CCB_TRANS_SYNC_RATE_VALID | CCB_TRANS_SYNC_OFFSET_VALID); /* drop all disconnected CCBs and clean negotiations */ for(targ=0; targ <= OUR_MAX_SUPPORTED_TARGET; targ++) { clean_negotiations(softc, targ); /* report the event if possible */ if(xpt_create_path(&path, /*periph*/NULL, cam_sim_path(sim), targ, CAM_LUN_WILDCARD) == CAM_REQ_CMP) { xpt_async(AC_TRANSFER_NEG, path, &neg); xpt_free_path(path); } for(lun=0; lun <= OUR_MAX_SUPPORTED_LUN; lun++) for(h = softc->first_discon_hcb[targ][lun]; h != NULL; h = hh) { hh=h->next; if(fatal) free_hcb_and_ccb_done(h, h->ccb, CAM_UNREC_HBA_ERROR); else free_hcb_and_ccb_done(h, h->ccb, CAM_SCSI_BUS_RESET); } } /* report the event */ xpt_async(AC_BUS_RESET, softc->wpath, NULL); /* re-initialization may take a lot of time, in such case * its completion should be signaled by another interrupt or * checked on timeout - but for simplicity we assume here that * it is really fast */ if(!fatal) { reinitialize_controller_without_scsi_reset(softc); } else { reinitialize_controller_with_scsi_reset(softc); } schedule_next_hcb(softc); return; } If interrupt is not caused by a controller-wide condition then probably something has happened to the current hardware control block. Depending on the hardware there may be other non-HCB-related events, we just do not consider them here. Then we analyze what happened to this HCB: struct xxx_hcb *hcb, *h, *hh; int hcb_status, scsi_status; int ccb_status; int targ; int lun_to_freeze; hcb = get_current_hcb(softc); if(hcb == NULL) { /* either stray interrupt or something went very wrong * or this is something hardware-dependent */ handle as necessary; return; } targ = hcb->target; hcb_status = get_status_of_current_hcb(softc); First we check if the HCB has completed and if so we check the returned SCSI status. if(hcb_status == COMPLETED) { scsi_status = get_completion_status(hcb); Then look if this status is related to the REQUEST SENSE command and if so handle it in a simple way. if(hcb->flags & DOING_AUTOSENSE) { if(scsi_status == GOOD) { /* autosense was successful */ hcb->ccb->ccb_h.status |= CAM_AUTOSNS_VALID; free_hcb_and_ccb_done(hcb, hcb->ccb, CAM_SCSI_STATUS_ERROR); } else { autosense_failed: free_hcb_and_ccb_done(hcb, hcb->ccb, CAM_AUTOSENSE_FAIL); } schedule_next_hcb(softc); return; } Else the command itself has completed, pay more attention to details. If auto-sense is not disabled for this CCB and the command has failed with sense data then run REQUEST SENSE command to receive that data. hcb->ccb->csio.scsi_status = scsi_status; calculate_residue(hcb); if( (hcb->ccb->ccb_h.flags & CAM_DIS_AUTOSENSE)==0 && ( scsi_status == CHECK_CONDITION || scsi_status == COMMAND_TERMINATED) ) { /* start auto-SENSE */ hcb->flags |= DOING_AUTOSENSE; setup_autosense_command_in_hcb(hcb); restart_current_hcb(softc); return; } if(scsi_status == GOOD) free_hcb_and_ccb_done(hcb, hcb->ccb, CAM_REQ_CMP); else free_hcb_and_ccb_done(hcb, hcb->ccb, CAM_SCSI_STATUS_ERROR); schedule_next_hcb(softc); return; } One typical thing would be negotiation events: negotiation messages received from a SCSI target (in answer to our negotiation attempt or by target's initiative) or the target is unable to negotiate (rejects our negotiation messages or does not answer them). switch(hcb_status) { case TARGET_REJECTED_WIDE_NEG: /* revert to 8-bit bus */ softc->current_bus_width[targ] = softc->goal_bus_width[targ] = 8; /* report the event */ neg.bus_width = 8; neg.valid = CCB_TRANS_BUS_WIDTH_VALID; xpt_async(AC_TRANSFER_NEG, hcb->ccb.ccb_h.path_id, &neg); continue_current_hcb(softc); return; case TARGET_ANSWERED_WIDE_NEG: { int wd; wd = get_target_bus_width_request(softc); if(wd <= softc->goal_bus_width[targ]) { /* answer is acceptable */ softc->current_bus_width[targ] = softc->goal_bus_width[targ] = neg.bus_width = wd; /* report the event */ neg.valid = CCB_TRANS_BUS_WIDTH_VALID; xpt_async(AC_TRANSFER_NEG, hcb->ccb.ccb_h.path_id, &neg); } else { prepare_reject_message(hcb); } } continue_current_hcb(softc); return; case TARGET_REQUESTED_WIDE_NEG: { int wd; wd = get_target_bus_width_request(softc); wd = min (wd, OUR_BUS_WIDTH); wd = min (wd, softc->user_bus_width[targ]); if(wd != softc->current_bus_width[targ]) { /* the bus width has changed */ softc->current_bus_width[targ] = softc->goal_bus_width[targ] = neg.bus_width = wd; /* report the event */ neg.valid = CCB_TRANS_BUS_WIDTH_VALID; xpt_async(AC_TRANSFER_NEG, hcb->ccb.ccb_h.path_id, &neg); } prepare_width_nego_rsponse(hcb, wd); } continue_current_hcb(softc); return; } Then we handle any errors that could have happened during auto-sense in the same simple-minded way as before. Otherwise we look closer at the details again. if(hcb->flags & DOING_AUTOSENSE) goto autosense_failed; switch(hcb_status) { The next event we consider is unexpected disconnect. Which is considered normal after an ABORT or BUS DEVICE RESET message and abnormal in other cases. case UNEXPECTED_DISCONNECT: if(requested_abort(hcb)) { /* abort affects all commands on that target+LUN, so * mark all disconnected HCBs on that target+LUN as aborted too */ for(h = softc->first_discon_hcb[hcb->target][hcb->lun]; h != NULL; h = hh) { hh=h->next; free_hcb_and_ccb_done(h, h->ccb, CAM_REQ_ABORTED); } ccb_status = CAM_REQ_ABORTED; } else if(requested_bus_device_reset(hcb)) { int lun; /* reset affects all commands on that target, so * mark all disconnected HCBs on that target+LUN as reset */ for(lun=0; lun <= OUR_MAX_SUPPORTED_LUN; lun++) for(h = softc->first_discon_hcb[hcb->target][lun]; h != NULL; h = hh) { hh=h->next; free_hcb_and_ccb_done(h, h->ccb, CAM_SCSI_BUS_RESET); } /* send event */ xpt_async(AC_SENT_BDR, hcb->ccb->ccb_h.path_id, NULL); /* this was the CAM_RESET_DEV request itself, it is completed */ ccb_status = CAM_REQ_CMP; } else { calculate_residue(hcb); ccb_status = CAM_UNEXP_BUSFREE; /* request the further code to freeze the queue */ hcb->ccb->ccb_h.status |= CAM_DEV_QFRZN; lun_to_freeze = hcb->lun; } break; If the target refuses to accept tags we notify CAM about that and return back all commands for this LUN: case TAGS_REJECTED: /* report the event */ neg.flags = 0 & ~CCB_TRANS_TAG_ENB; neg.valid = CCB_TRANS_TQ_VALID; xpt_async(AC_TRANSFER_NEG, hcb->ccb.ccb_h.path_id, &neg); ccb_status = CAM_MSG_REJECT_REC; /* request the further code to freeze the queue */ hcb->ccb->ccb_h.status |= CAM_DEV_QFRZN; lun_to_freeze = hcb->lun; break; Then we check a number of other conditions, with processing basically limited to setting the CCB status: case SELECTION_TIMEOUT: ccb_status = CAM_SEL_TIMEOUT; /* request the further code to freeze the queue */ hcb->ccb->ccb_h.status |= CAM_DEV_QFRZN; lun_to_freeze = CAM_LUN_WILDCARD; break; case PARITY_ERROR: ccb_status = CAM_UNCOR_PARITY; break; case DATA_OVERRUN: case ODD_WIDE_TRANSFER: ccb_status = CAM_DATA_RUN_ERR; break; default: /* all other errors are handled in a generic way */ ccb_status = CAM_REQ_CMP_ERR; /* request the further code to freeze the queue */ hcb->ccb->ccb_h.status |= CAM_DEV_QFRZN; lun_to_freeze = CAM_LUN_WILDCARD; break; } Then we check if the error was serious enough to freeze the input queue until it gets proceeded and do so if it is: if(hcb->ccb->ccb_h.status & CAM_DEV_QFRZN) { /* freeze the queue */ xpt_freeze_devq(ccb->ccb_h.path, /*count*/1); /* re-queue all commands for this target/LUN back to CAM */ for(h = softc->first_queued_hcb; h != NULL; h = hh) { hh = h->next; if(targ == h->targ && (lun_to_freeze == CAM_LUN_WILDCARD || lun_to_freeze == h->lun) ) free_hcb_and_ccb_done(h, h->ccb, CAM_REQUEUE_REQ); } } free_hcb_and_ccb_done(hcb, hcb->ccb, ccb_status); schedule_next_hcb(softc); return; This concludes the generic interrupt handling although specific controllers may require some additions. Errors Summary When executing an I/O request many things may go wrong. The reason of error can be reported in the CCB status with great detail. Examples of use are spread throughout this document. For completeness here is the summary of recommended responses for the typical error conditions: CAM_RESRC_UNAVAIL - some resource is temporarily unavailable and the SIM driver cannot generate an event when it will become available. An example of this resource would be some intra-controller hardware resource for which the controller does not generate an interrupt when it becomes available. CAM_UNCOR_PARITY - unrecovered parity error occurred CAM_DATA_RUN_ERR - data overrun or unexpected data phase (going in other direction than specified in CAM_DIR_MASK) or odd transfer length for wide transfer CAM_SEL_TIMEOUT - selection timeout occurred (target does not respond) CAM_CMD_TIMEOUT - command timeout occurred (the timeout function ran) CAM_SCSI_STATUS_ERROR - the device returned error CAM_AUTOSENSE_FAIL - the device returned error and the REQUEST SENSE COMMAND failed CAM_MSG_REJECT_REC - MESSAGE REJECT message was received CAM_SCSI_BUS_RESET - received SCSI bus reset CAM_REQ_CMP_ERR - impossible SCSI phase occurred or something else as weird or just a generic error if further detail is not available CAM_UNEXP_BUSFREE - unexpected disconnect occurred CAM_BDR_SENT - BUS DEVICE RESET message was sent to the target CAM_UNREC_HBA_ERROR - unrecoverable Host Bus Adapter Error CAM_REQ_TOO_BIG - the request was too large for this controller CAM_REQUEUE_REQ - this request should be re-queued to preserve transaction ordering. This typically occurs when the SIM recognizes an error that should freeze the queue and must place other queued requests for the target at the sim level back into the XPT queue. Typical cases of such errors are selection timeouts, command timeouts and other like conditions. In such cases the troublesome command returns the status indicating the error, the and the other commands which have not be sent to the bus yet get re-queued. CAM_LUN_INVALID - the LUN ID in the request is not supported by the SCSI controller CAM_TID_INVALID - the target ID in the request is not supported by the SCSI controller Timeout Handling When the timeout for an HCB expires that request should be aborted, just like with an XPT_ABORT request. The only difference is that the returned status of aborted request should be CAM_CMD_TIMEOUT instead of CAM_REQ_ABORTED (that is why implementation of the abort better be done as a function). But there is one more possible problem: what if the abort request itself will get stuck? In this case the SCSI bus should be reset, just like with an XPT_RESET_BUS request (and the idea about implementing it as a function called from both places applies here too). Also we should reset the whole SCSI bus if a device reset request got stuck. So after all the timeout function would look like: static void xxx_timeout(void *arg) { struct xxx_hcb *hcb = (struct xxx_hcb *)arg; struct xxx_softc *softc; struct ccb_hdr *ccb_h; softc = hcb->softc; ccb_h = &hcb->ccb->ccb_h; if(hcb->flags & HCB_BEING_ABORTED || ccb_h->func_code == XPT_RESET_DEV) { xxx_reset_bus(softc); } else { xxx_abort_ccb(hcb->ccb, CAM_CMD_TIMEOUT); } } When we abort a request all the other disconnected requests to the same target/LUN get aborted too. So there appears a question, should we return them with status CAM_REQ_ABORTED or CAM_CMD_TIMEOUT? The current drivers use CAM_CMD_TIMEOUT. This seems logical because if one request got timed out then probably something really bad is happening to the device, so if they would not be disturbed they would time out by themselves.