svn commit: r224842 - head/sys/kern

[Robert Watson]

On Sun, 14 Aug 2011, Alexander Best wrote:

>> It might be worth mentioning this in UPDATING or similar, since a kernel 
>> built with clang (I haven't tried gcc) during this window will make it 
>> impossible to do a buildworld without first rebuilding the kernel with this 
>> fix. It also seems to break at least portsnap, and possibly other tools as 
>> well.
>
> +1. please also mention the KPI change to fget()! so many people have had 
> issues, where 3rd party drivers - mostly the nvidia binary driver - got 
> broken.

The nVidia driver is rare in that it uses the file descriptor interfaces from 
inside a third-party driver.  Most third-party drivers plug into much more 
limited subsets of the kernel -- newbus, busdma, the ifnet interface, the disk 
interface, CAM, USB, etc.  The reason to merge this change now was to ensure 
that 9.0 shipped with the interface in its final form rather than have to try 
to work around the existing modules for 9.1.  However, I would comment more 
generally that device drivers that use interfaces outside of the kernel device 
driver KPIs are inherently fragile.

(Not sure there's anything to be done about that in the nVidia case).

(Per previous e-mail, I have queued a request to re@ to update UPDATING).

Robert