modesetting and DRI2/3

[zahlenmeer at gmx.de]

This raises more questions than it answers.
The modesetting driver uses DRI3 by default, and I haven't touched the
defaults. Compiling with the --disable-dri2 flag should work, but then I
get "failed to initalize the DRI2 extension" errors in my log file.
If you say that VDPAU still relies on DRI2 I totally understand the
errors, but I don't need VDPAU (only Intel graphics, so VAAPI) and I
also don't have it installed and mesa is compiled without VDPAU support.
So why does xorg load it? (I am not sure what exactly is responsible for
the VDPAU line in my logs, but I interpret is as Xorg loading this driver)

On 08/05/16 13:09, Steven Newbury wrote:
> On Wed, 2016-07-27 at 18:24 +0200, zahlenmeer at gmx.de wrote:
>> Hey everyone,
>> I am struggling to understand how the modesetting driver and DRI play
>> together.
>> This is from Xorg.0.log:
>>
>> [  2350.977] (II) Loading
>> /usr/lib/xorg/modules/drivers/modesetting_drv.so
>> [  2350.977] (II) modeset(0): using drv /dev/dri/card0
>> [  2350.984] (II) glamor: OpenGL accelerated X.org driver based.
>> [  2351.387] (II) modeset(0): [DRI2]   DRI driver: i965
>> [  2351.387] (II) modeset(0): [DRI2]   VDPAU driver: i965
>>
>> And this is from glxinfo:
>>
>> libGL: Using DRI3 for screen 0
>>
>> I read that modesetting uses DRI3 by default so I am a bit surprised
>> to
>> read something like "modeset(0): [DRI2]" in my logs. I also tried and
>> compiled xorg with the --disable-dri2 flag. In this case I get aiglx
>> errors that modesetting failed to initalize the DRI2 extension.
>> Could anyone explain this behaviour to me?
>>
>> Kind regards
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> 
> VDPAU doesn't use DRI3 as yet, AFAIK.
> 
> DRI2 is still available unless it's build time disabled, even if DRI3
> is default.
>