[Mesa-dev] [PATCH 0/2] Turning swrast into DRI2 drivers

[Giovanni Campagna]

2014-04-14 22:37 GMT+02:00 Dave Airlie <airlied at gmail.com>:
> On Sat, Apr 12, 2014 at 10:25 AM, Giovanni Campagna
> <scampa.giovanni at gmail.com> wrote:
>> Hi everyone,
>>
>> Some time ago I sent patches to enable the swrast driver on
>> GBM/DRM, and I did them in the dumbest way possible (that is,
>> having GBM implement the dri-swrast interface), to make sure
>> it would work without kernel support.
>> This patch series is a little smarter, in that it creates
>> more than one KMS buffer and has llvmpipe render directly
>> into the KMS buffer, so we don't need to copy from the back
>> to the shadow (before the kernel copies from the shadow to
>> the front).
>>
>> For background, this is necessary to get mutter-wayland running
>> inside VMs such as gnome-continuous, which has a qxl DRM driver.
>> mutter-wayland only has a KMS/EGL rendering backend, and we
>> have no intention to add pixman or fbdev.
>> GNOME bug: https://bugzilla.gnome.org/show_bug.cgi?id=728059
>>
>> The older patches were http://lists.freedesktop.org/archives/mesa-dev/2014-March/055113.html
>> I can rebase if so is desired.
>
> I actually did something similiar that was qxl specific before,
> (qxl-dri2-driver in my repo, though it had some problems I can barely
> remember now), the only question I have is what does this produce?
> another swrast_dri.so? and will it have any affect on current
> scenarios?

The first patch (the one in the previous mail) only affects the
loader, not the driver, so it works with the current swrast_dri. This
set produces a swrast_dri2_dri.so, which is loaded only under the
drm+gbm+dri backend, so it does not affect drisw+x11 and
drisw+wayland.
Also, it's not qxl specific, as far i'm told, because it uses the dumb
ioctls, not the qxl gem. A qxl userspace driver with proper gem
buffersharing would allow us to use it for accelerating composition on
x11 too, but I'm not sure it's a real benefit, with wayland around the
corner.

Giovanni