[PATCH] kernel/drm: vblank wait on crtc > 1

Mario Kleiner mario.kleiner at tuebingen.mpg.de
Sat Mar 19 10:30:57 PDT 2011

> On Fri, 18 Mar 2011, Jesse Barnes wrote:
>> I like the new param check, but I'd still prefer a new ioctl to  
>> abusing
>> the old one.
> It's not "abusing" it but extending the interface in a
> backwards-compatible manner. Introducing a new one would result in two
> ioctls that essentially do the same thing, which I don't like.

> On Fri, 18 Mar 2011, Jesse Barnes wrote:

 > Yes abusing was a strong word; I just don't like encoding crtc  
 > in a bitfield, when we just use ints everywhere else.
 > Not a big deal, Dave will make the final call.  Thanks for doing this
 > work.
 > --
 > Jesse Barnes, Intel Open Source Technology Center


A clean solution with int's in a new ioctl() would be certainly  
nicer. But if we'd define a waitvblank ioctl() v2, we should probably  
fix other limitations of the old one as well.

E.g., the kernel's vblank counter is only 32 bit. The api /  
oml_sync_control extension / mesa/ x etc. expose a 64 bit vblank  
counter. At the moment we work around this by masking out the upper  
32 bit in the ddx, accepting some small skipped frame glitch every  
couple of months of uptime when the "64 bit" counter wraps around  
already at 32 bits. This is something we should probably fix in a  
ioctl() v2 as well.

Take this just as my vote for Ilja's solution as a workable stop-gap  
measure for fixing an existing problem until we implement a more  
permanent solution for a new ioctl().


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