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[man] Add documentation for OpenFirmware API
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Authored by gonzo on Feb 26 2018, 1:34 AM.
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Details

Summary

Add man pages for number of OF_* functions that are used
in OpenFirmware-compatible systems. Please note that
documentation in OF_getprop.9 does not match current
property management API but matches what it will be
once functional and style bugs are fixed. This diff
will not be committed until API is fixed I just want
to start editorial review as sson as possible.

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Build 15413: arc lint + arc unit

Event Timeline

There is a lot of redundancy in the "The function returns" sentences, which could be shortened by saying just "Returns" or rearranging some in a different order, like "Zero is returned..."

share/man/man9/OF_child.9
49
returns the phandle value of the first child of the
51
Zero is returned if there are no child nodes.
54
returns the phandle for the parent of the
55
.Fa node .
56
Zero is returned if
61
returns the phandle value of the next sibling of the
63
Zero is returned if there is no sibling node.
share/man/man9/OF_device_from_xref.9
48
When a device tree node references another node, the driver may
49
need to get the device associated with the referenced node.

"get the device" needs to be more specific. Get a device_t instance?

50
For instance, an Ethernet driver accessing a PHY device.
51
To make this possible, the kernel maintains a table that
55
adds a map entry from the effective phandle
59
If a mapping entry for
61
already exists, it is replaced with the new one.
65
returns a device_t instance associated with the effective phandle
70
returns the effective phandle associated with the device
72
If no such mapping exists, the function returns 0.
share/man/man9/OF_finddevice.9
43
returns the phandle for the node specified by the
45
Returns -1 if the path cannot be found in the tree.
47
The return value should only be checked with equality
48

Make this more language-agnostic:

operators (equal to, not equal to) and not relational comparison
49

As above, and start new sentences on new lines.

(less than, greater than).
There is a discrepancy between the IEEE 1275 standard and
50
the
.Fx Ns 's
internal representation of a phandle: IEEE 1275
51
requires the return value of this function to be -1 if the path
52

Break sentence:

is not found.
But phandle_t is an unsigned type, so it cannot
53
be relationally compared with -1 or 0, which

I'm not sure if "relationally" is the right word. I can think of others like "accurately" or "properly", but they don't seem much better.

share/man/man9/OF_getprop.9
80
Device nodes can have associated properties.
81
Properties consist of a name and a value.
83
A value is an array of zero or more bytes that encode certain
87
values or any combination of these types.
89
Properties with a zero-byte length value usually represent boolean

Is the length being a byte value relevant if it is zero? Could we just say

Properties with a zero-length value usually represent boolean
93

Possessive adds no value here:

A byte array is encoded as a sequence of bytes and represents
96
A text string is a sequence of n printable characters.
It is
98
characters represented as bytes plus a terminating null character.
108
or 0 if the property exists but has no associated value.
109
If
.Fa propname
does not exist, -1 is returned.
114
copies a maximum of
122
The function returns the actual size of the value or -1 if the
126
copies a maximum of
130
then converts cell values from big-endian to host byte order.
131
The function returns the actual size of the value in bytes, or -1
134

Spelling, but also unclear. Will it still work if len is not a multiple of 4? If not, this should say "must".

must be a multiple of 4.
139
has a property specified by
141
or zero if the property does not exist.
149
If the property is found, the function copies a maximum of
154
The function returns the actual size in bytes of the value,
155
or -1 if the property does not exist.
163
If the property is found, the function copies a maximum of
168
then converts cell values from big-endian to host byte order.
169
The function returns the actual size in bytes of the value,
170
or -1 if the property does not exist.
173
allocates memory large enough to hold the
179
The function returns the actual size of the value and stores the
180
address of the allocated memory in
182
If the property has a zero-sized value,
185
The function returns -1 if the property does not exist or
190

Does "may sleep" mean I have permission to sleep while waiting for the memory allocation, or does it mean that the memory allocation might cause me to sleep? I suspect it's the second. So:

The function might sleep when allocating memory.
193
allocates enough memory to hold the
201
The actual size of the value is returned and the
202
address of allocated memory is stored in

Note: many of the previous sections had this copy/paste "The function returns", which is redundant and can be shortened this way.

204
If the property has a zero-length value,
206
is set to NULL.
207
The function returns -1 if the property does not exist or
212
The function might sleep when allocating memory.
217

Should this be

that was allocated by
219
or
223
copies a maximum of
225

Not clear. Maybe:

.Fn OF_nextprop
copies
.Fa size
bytes of the name of the property following
.Fa propname
252
If the property does not exist, the function tries to create
share/man/man9/OF_node_from_xref.9
48
For instance, a framebuffer controller may refer to a GPIO
50
For such implementations, the phandle is used by the kernel to
51
identify the node does not match the value of the cell property that
52

This sentence is difficult to understand.

53
Otherwise, the effective phandle is equal to the kernel phandle.
57
returns the kernel phandle for the effective phandle
59
If one cannot be found or the OpenFirmware implementation
61
the input value.
64
returns the effective phandle for the kernel phandle
66
If one cannot be found or the OpenFirmware implementation
68
the input value.
share/man/man9/OF_package_to_path.9
45
bytes of the fully qualified path to the device tree node
gonzo marked 78 inline comments as done.

Apply wblock@ edits and get rid of "The function returns"
in favor of just "Returns"

share/man/man9/OF_finddevice.9
53

By "relationally" I meant "using greater than, less than" as opposing to equality check. Maybe it can give you some hints on how to phrase this better.

share/man/man9/OF_getprop.9
190

It's the second.

225

I don't think it's the right description. Function copies name to buf, if the name length is larger than size, it copies only size bytes.

share/man/man9/OF_node_from_xref.9
52

I added more details to the example to illustrate the concept of reference.

This revision was not accepted when it landed; it landed in state Needs Review.Apr 9 2018, 10:24 PM
This revision was automatically updated to reflect the committed changes.