[PATCH xserver] present: disable page flip only when a slave crtc is active

[Michel Dänzer]

On 01/02/17 04:05 AM, David Airlie wrote:
>> From: "Michel Dänzer" <michel at daenzer.net>
>> On 26/01/17 07:13 PM, Qiang Yu wrote:
>>>
>>> @@ -145,7 +157,7 @@ present_check_flip(RRCrtcPtr    crtc,
>>>          return FALSE;
>>>  
>>>      /* Fail to flip if we have slave outputs */
>>> -    if (screen->output_slaves)
>>> +    if (screen->output_slaves &&
>>> present_check_output_slaves_active(screen))
>>>          return FALSE;
>>>  
>>>      /* Make sure the window hasn't been redirected with Composite */
>>>
>>
>> Actually, I'm not sure why we need to check for slave outputs here at
>> all. Dave, did you run into an actual problem without the check, or was
>> it just a theoretical concern? The commit log says:
> 
> You don't get an output on USB without the fix.

Hmm, why not? Flipping just replaces the screen pixmap's storage;
copying from the screen pixmap to the shared pixmap should still work
fine, and flips generate the damage needed to trigger it as well.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer