On Tue, Jul 31, 2018 at 4:48 AM, Michel Dänzer <michel at daenzer.net> wrote:
> On 2018-07-30 08:12 PM, Alex Deucher wrote:
>> On Fri, Jul 27, 2018 at 12:04 PM, Michel Dänzer <michel at daenzer.net> wrote:
>>> From: Michel Dänzer <michel.daenzer at amd.com>
>>>
>>> We were only storing the FB provided by the client, but on CRTCs with
>>> TearFree enabled, we use a separate FB. This could cause
>>> drmmode_flip_handler to fail to clear drmmode_crtc->flip_pending, which
>>> could result in a hang when waiting for the pending flip to complete. We
>>> were trying to avoid that by always clearing drmmode_crtc->flip_pending
>>> when TearFree is enabled, but that wasn't reliable, because
>>> drmmode_crtc->tear_free can already be FALSE at this point when
>>> disabling TearFree.
>>>
>>> Now that we're keeping track of each CRTC's flip FB separately,
>>> drmmode_flip_handler can reliably clear flip_pending, and we no longer
>>> need the TearFree hack.
>>>
>>> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
>>>
>>> [...]
>>>
>>> @@ -82,6 +81,7 @@ typedef struct {
>>> xf86CrtcPtr fe_crtc;
>>> amdgpu_drm_handler_proc handler;
>>> amdgpu_drm_abort_proc abort;
>>> + struct drmmode_fb *fb[0];
>>
>> Don't some compilers have problems with zero sized arrays?
>
> Are you thinking of
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5b7d245009e734588e553092f5c0b0bd788b3a55
> ? Per https://bugs.freedesktop.org/show_bug.cgi?id=66932#c24 , the
> problem there was variable sized arrays being declared as [1], which
> obviously can't work.
>
> Declaring a [0] array at the end of a struct is a GCC extension, see
> https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero-Length . clang
> seems to handle this fine as well.
>
> An alternative would be using the C99 syntax "[];" instead, but I think
> the above is fine in this case.
Yup, that was the issue I was thinking of. No other concerns.
Alex
>
>
>> Other than that looks good to me:
>> Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
>
> Thanks!
>
>
> --
> Earthling Michel Dänzer | http://www.amd.com
> Libre software enthusiast | Mesa and X developer
