Re: [RfC PATCH] drm: fourcc byteorder: brings header file comments in line with reality.

[Ilia Mirkin <imirkin@alum.mit.edu>]

On Mon, Apr 10, 2017 at 11:09 AM, Pekka Paalanen <ppaalanen@gmail.com> wrote:
> On Mon, 10 Apr 2017 16:17:27 +0200
> Gerd Hoffmann <kraxel@redhat.com> wrote:
>
>>   Hi,
>>
>> > which software have you used as representative of "reality"?
>>
>> ppc64 (big endian) virtual machine, running with qemu stdvga & bochs-drm
>> driver.  Xorg with modesetting driver uses DRM_FORMAT_XRGB8888 (one and
>> only format supported by bochs-drm), and we have to interpret that in
>> bigendian byte order on the host side to get a correct display.
>
> I wonder if that is just an oversight from trying to match OpenGL
> formats to DRM formats. It's full of gotcha's.
>
> Did you try with GLAMOR? Do you see a difference with and without
> GLAMOR? Hmm, but you have no GPU support, so GLAMOR would be through a
> Mesa software renderer? I think I heard someone say something about
> Mesa software on BE...
>
> But even if this actually is a valid example of software we must keep
> working as is, well, ouch. But if I cannot show that your fix breaks
> anything, then I suppose you win. Your proposal would certainly solve
> the dilemma we have with wl_shm formats in Wayland.
>
> I also wonder if a real BE machine could have different results than
> the virtual machine.

I have a PPC G5 with an AGP GeForce FX 5200 that I can test things on,
if necessary. (I got it specifically for this purpose, as the people
who use this type of hw daily tend to perform updates rarely... in no
small part due to the fact that updates tend to break the HW.)

Just let know what you need tested, I should be able to turn it around
within a couple of days.

Cheers,

  -ilia