[git pull] drm for 5.8-rc1

[Thierry Reding]

On Thu, Aug 13, 2020 at 03:00:37PM +0200, Karol Herbst wrote:
> At least for now I've created an MR to revert the change:
> https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6300
> 
> But it seems like there was probably a good reason why it got added?
> Happy to have better fixes, but that's the best we've got so far I
> think?
> 
> Thierry, what do you think?

I did find the following via my mailbox (finally collecting all those
emails is paying off =):

	https://lists.freedesktop.org/archives/mesa-dev/2018-May/196026.html

Cc'ing Daniel on the off chance that he remembers what the use-case was.

I vaguely recall that Daniel was pointing out an issue on IRC that
caused a series of fixes, including this change. Given that this was all
done because of framebuffer modifiers, I think my earlier hunch about
this being related to the case of non-modifier userspace is correct and
we do run into issues with userspace that doesn't use framebuffer
modifiers at all. In that case we basically have to assume pitch-linear
because userspace will use DRM_IOCTL_MODE_ADDFB, which doesn't support
modifiers.

Thierry
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/dri-devel/attachments/20200814/f6d9a7b1/attachment.sig>