coretemp(4)/amdtemp(4) and sysctl nodes

[John Baldwin]

On Friday, December 03, 2010 1:05:02 pm mdf at freebsd.org wrote:
> There are very few uses in FreeBSD mainline code of
> sysctl_remove_oid(), and I was looking at potentially removing them.
> However, the use in coretemp/amdtemp has me slightly stumped.
> 
> Each device provides a device_get_sysctl_ctx sysctl_ctx that is
> automatically cleaned up when the device goes away.  Yet the sysctl
> nodes for both amdtemp and coretemp use the context of other devices,
> rather than their own.  I can't quite figure out why, though the two
> are slightly different enough that they may have different reasons.
> 
> For coretmp(4) I don't see how the parent device can be removed first,
> since we are a child device.  So from my understanding it makes no
> sense to have an explicit sysctl_remove_oid() and attach in the
> parent's sysctl_ctx.

Well, you would want 'kldunload coretemp.ko' to remove the sysctl node even 
though the parent device is still around.  I suspect the same case is true
for amdtemp.  Probably these drivers should use a separate sysctl context.
I'm not sure how the sysctl code handles removing a node that has an active 
context though.

-- 
John Baldwin