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

[Alex Deucher]

On Sat, Mar 19, 2011 at 1:30 PM, Mario Kleiner
<mario.kleiner at tuebingen.mpg.de> wrote:
>>
>> 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 numbers
>> 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
>
> Hi
>
> 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().

I agree.  I think this is a good stop-gap to support >2 crtcs until we
design a better ioctl.

Alex

>
> best,
> -mario
>
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