Index: sys/amd64/amd64/prof_machdep.c
===================================================================
--- sys/amd64/amd64/prof_machdep.c
+++ sys/amd64/amd64/prof_machdep.c
@@ -245,7 +245,8 @@
 }
 
 SYSCTL_PROC(_machdep, OID_AUTO, cputime_clock, CTLTYPE_INT | CTLFLAG_RW,
-	    0, sizeof(u_int), sysctl_machdep_cputime_clock, "I", "");
+    0, sizeof(u_int), sysctl_machdep_cputime_clock, "I",
+    "CPU clock time");
 
 /*
  * The start and stop routines need not be here since we turn off profiling
Index: sys/dev/sio/sio.c
===================================================================
--- sys/dev/sio/sio.c
+++ sys/dev/sio/sio.c
@@ -291,10 +291,12 @@
 int	comconsole = -1;
 static	volatile speed_t	comdefaultrate = CONSPEED;
 static	u_long			comdefaultrclk = DEFAULT_RCLK;
-SYSCTL_ULONG(_machdep, OID_AUTO, conrclk, CTLFLAG_RW, &comdefaultrclk, 0, "");
+SYSCTL_ULONG(_machdep, OID_AUTO, conrclk, CTLFLAG_RW, &comdefaultrclk, 0,
+    "Default register clock speed");
 static	speed_t			gdbdefaultrate = GDBSPEED;
 SYSCTL_UINT(_machdep, OID_AUTO, gdbspeed, CTLFLAG_RW,
-	    &gdbdefaultrate, GDBSPEED, "");
+    &gdbdefaultrate, GDBSPEED,
+    "Default serial GDB speed");
 static	u_int	com_events;	/* input chars + weighted output completions */
 static	Port_t	siocniobase;
 static	int	siocnunit = -1;
@@ -374,8 +376,9 @@
 	return error;
 }
 
-SYSCTL_PROC(_machdep, OID_AUTO, conspeed, CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_NOFETCH,
-	    0, 0, sysctl_machdep_comdefaultrate, "I", "");
+SYSCTL_PROC(_machdep, OID_AUTO, conspeed, CTLTYPE_INT | CTLFLAG_RWTUN |
+    CTLFLAG_NOFETCH, 0, 0, sysctl_machdep_comdefaultrate, "I",
+    "Default console speed");
 TUNABLE_INT("machdep.conspeed", __DEVOLATILE(int *, &comdefaultrate));
 
 #define SET_FLAG(dev, bit) device_set_flags(dev, device_get_flags(dev) | (bit))
Index: sys/i386/bios/apm.c
===================================================================
--- sys/i386/bios/apm.c
+++ sys/i386/bios/apm.c
@@ -144,12 +144,18 @@
 	}								\
 } while (0)
 
-SYSCTL_INT(_machdep, OID_AUTO, apm_suspend_delay, CTLFLAG_RW, &apm_suspend_delay, 1, "");
-SYSCTL_INT(_machdep, OID_AUTO, apm_standby_delay, CTLFLAG_RW, &apm_standby_delay, 1, "");
-SYSCTL_INT(_debug, OID_AUTO, apm_debug, CTLFLAG_RW, &apm_debug, 0, "");
+SYSCTL_INT(_machdep, OID_AUTO, apm_suspend_delay, CTLFLAG_RW,
+    &apm_suspend_delay, 1,
+    "Delay before entering suspend");
+SYSCTL_INT(_machdep, OID_AUTO, apm_standby_delay, CTLFLAG_RW,
+    &apm_standby_delay, 1,
+    "Delay before entering standby");
+SYSCTL_INT(_debug, OID_AUTO, apm_debug, CTLFLAG_RW, &apm_debug, 0,
+    "APM debug level");
 
 SYSCTL_INT(_machdep, OID_AUTO, apm_swab_batt_minutes, CTLFLAG_RWTUN,
-	   &apm_swab_batt_minutes, 0, "Byte swap battery time value.");
+    &apm_swab_batt_minutes, 0,
+    "Whether battery time requires endian byte swap");
 
 /*
  * return  0 if the function successfull,
Index: sys/i386/i386/elan-mmcr.c
===================================================================
--- sys/i386/i386/elan-mmcr.c
+++ sys/i386/i386/elan-mmcr.c
@@ -321,7 +321,8 @@
 }
 
 SYSCTL_PROC(_machdep, OID_AUTO, elan_freq, CTLTYPE_UINT | CTLFLAG_RW,
-    0, sizeof (u_int), sysctl_machdep_elan_freq, "IU", "");
+    0, sizeof (u_int), sysctl_machdep_elan_freq, "IU",
+    "Elan timecounter frequency");
 
 /*
  * Positively identifying the Elan can only be done through the PCI id of
Index: sys/i386/i386/mp_clock.c
===================================================================
--- sys/i386/i386/mp_clock.c
+++ sys/i386/i386/mp_clock.c
@@ -82,7 +82,8 @@
 }
 
 SYSCTL_PROC(_machdep, OID_AUTO, piix_freq, CTLTYPE_INT | CTLFLAG_RW,
-    0, sizeof(u_int), sysctl_machdep_piix_freq, "I", "");
+    0, sizeof(u_int), sysctl_machdep_piix_freq, "I",
+    "PIIX timecounter frequency");
 
 static unsigned
 piix_get_timecount(struct timecounter *tc)
Index: sys/i386/i386/prof_machdep.c
===================================================================
--- sys/i386/i386/prof_machdep.c
+++ sys/i386/i386/prof_machdep.c
@@ -277,7 +277,8 @@
 }
 
 SYSCTL_PROC(_machdep, OID_AUTO, cputime_clock, CTLTYPE_INT | CTLFLAG_RW,
-	    0, sizeof(u_int), sysctl_machdep_cputime_clock, "I", "");
+    0, sizeof(u_int), sysctl_machdep_cputime_clock, "I",
+    "CPU clock time");
 
 /*
  * The start and stop routines need not be here since we turn off profiling
Index: sys/powerpc/aim/mmu_oea.c
===================================================================
--- sys/powerpc/aim/mmu_oea.c
+++ sys/powerpc/aim/mmu_oea.c
@@ -223,20 +223,27 @@
 u_int	moea_pvo_enter_calls = 0;
 u_int	moea_pvo_remove_calls = 0;
 u_int	moea_pte_spills = 0;
-SYSCTL_INT(_machdep, OID_AUTO, moea_pte_valid, CTLFLAG_RD, &moea_pte_valid,
-    0, "");
+SYSCTL_INT(_machdep, OID_AUTO, moea_pte_valid, CTLFLAG_RD,
+    &moea_pte_valid, 0,
+    "Number of valid pte entries");
 SYSCTL_INT(_machdep, OID_AUTO, moea_pte_overflow, CTLFLAG_RD,
-    &moea_pte_overflow, 0, "");
+    &moea_pte_overflow, 0,
+    "Number of pte overflow entries");
 SYSCTL_INT(_machdep, OID_AUTO, moea_pte_replacements, CTLFLAG_RD,
-    &moea_pte_replacements, 0, "");
-SYSCTL_INT(_machdep, OID_AUTO, moea_pvo_entries, CTLFLAG_RD, &moea_pvo_entries,
-    0, "");
+    &moea_pte_replacements, 0,
+    "Number of pte replacements");
+SYSCTL_INT(_machdep, OID_AUTO, moea_pvo_entries, CTLFLAG_RD,
+    &moea_pvo_entries, 0,
+    "Number of pvo entries");
 SYSCTL_INT(_machdep, OID_AUTO, moea_pvo_enter_calls, CTLFLAG_RD,
-    &moea_pvo_enter_calls, 0, "");
+    &moea_pvo_enter_calls, 0,
+    "Number of pvo enter calls");
 SYSCTL_INT(_machdep, OID_AUTO, moea_pvo_remove_calls, CTLFLAG_RD,
-    &moea_pvo_remove_calls, 0, "");
+    &moea_pvo_remove_calls, 0,
+    "Number of pvo remove calls");
 SYSCTL_INT(_machdep, OID_AUTO, moea_pte_spills, CTLFLAG_RD,
-    &moea_pte_spills, 0, "");
+    &moea_pte_spills, 0,
+    "Number of pte spills");
 
 /*
  * Allocate physical memory for use in moea_bootstrap.
Index: sys/powerpc/aim/mmu_oea64.c
===================================================================
--- sys/powerpc/aim/mmu_oea64.c
+++ sys/powerpc/aim/mmu_oea64.c
@@ -173,8 +173,9 @@
 static int	moea64_bpvo_pool_index = 0;
 static int	moea64_bpvo_pool_size = 327680;
 TUNABLE_INT("machdep.moea64_bpvo_pool_size", &moea64_bpvo_pool_size);
-SYSCTL_INT(_machdep, OID_AUTO, moea64_allocated_bpvo_entries, CTLFLAG_RD, 
-    &moea64_bpvo_pool_index, 0, "");
+SYSCTL_INT(_machdep, OID_AUTO, moea64_allocated_bpvo_entries, CTLFLAG_RD,
+    &moea64_bpvo_pool_index, 0,
+    "Current index of the bvpo pool");
 
 #define	VSID_NBPW	(sizeof(u_int32_t) * 8)
 #ifdef __powerpc64__
@@ -196,16 +197,21 @@
 u_int	moea64_pvo_entries = 0;
 u_int	moea64_pvo_enter_calls = 0;
 u_int	moea64_pvo_remove_calls = 0;
-SYSCTL_INT(_machdep, OID_AUTO, moea64_pte_valid, CTLFLAG_RD, 
-    &moea64_pte_valid, 0, "");
+SYSCTL_INT(_machdep, OID_AUTO, moea64_pte_valid, CTLFLAG_RD,
+    &moea64_pte_valid, 0,
+    "Number of valid pte entries");
 SYSCTL_INT(_machdep, OID_AUTO, moea64_pte_overflow, CTLFLAG_RD,
-    &moea64_pte_overflow, 0, "");
-SYSCTL_INT(_machdep, OID_AUTO, moea64_pvo_entries, CTLFLAG_RD, 
-    &moea64_pvo_entries, 0, "");
+    &moea64_pte_overflow, 0,
+    "Number of pte overflow entries");
+SYSCTL_INT(_machdep, OID_AUTO, moea64_pvo_entries, CTLFLAG_RD,
+    &moea64_pvo_entries, 0,
+    "Number of pvo entries");
 SYSCTL_INT(_machdep, OID_AUTO, moea64_pvo_enter_calls, CTLFLAG_RD,
-    &moea64_pvo_enter_calls, 0, "");
+    &moea64_pvo_enter_calls, 0,
+    "Number of pvo enter calls");
 SYSCTL_INT(_machdep, OID_AUTO, moea64_pvo_remove_calls, CTLFLAG_RD,
-    &moea64_pvo_remove_calls, 0, "");
+    &moea64_pvo_remove_calls, 0,
+    "Number of pvo remove calls");
 
 vm_offset_t	moea64_scratchpage_va[2];
 struct pvo_entry *moea64_scratchpage_pvo[2];
Index: sys/powerpc/powerpc/machdep.c
===================================================================
--- sys/powerpc/powerpc/machdep.c
+++ sys/powerpc/powerpc/machdep.c
@@ -153,7 +153,8 @@
 SYSINIT(cpu, SI_SUB_CPU, SI_ORDER_FIRST, cpu_startup, NULL);
 
 SYSCTL_INT(_machdep, CPU_CACHELINE, cacheline_size,
-	   CTLFLAG_RD, &cacheline_size, 0, "");
+    CTLFLAG_RD, &cacheline_size, 0,
+    "Cacheline size");
 
 uintptr_t	powerpc_init(vm_offset_t, vm_offset_t, vm_offset_t, void *,
 		    uint32_t);