Hi, On Wed, Mar 6, 2024 at 4:07 AM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote: > > Hi, > > sorry that I did not see the patch before. > > Am 27.02.24 um 23:19 schrieb Douglas Anderson: > > Even though the UDL driver converts to RGB565 internally (see > > pixel32_to_be16() in udl_transfer.c), it advertises XRGB8888 for > > compatibility. Let's add ARGB8888 to that list. > > We had a heated discussion about the emulation of color formats. It was > decided that XRGB8888 is the only format to support; and that's only > because legacy userspace sometimes expects it. Adding other formats to > the list should not be done easily. Sorry! I wasn't aware of the previous discussion and nobody had brought it up till now. As discussed on #dri-devel IRC, I've posted a revert: https://lore.kernel.org/r/20240306063721.1.I4a32475190334e1fa4eef4700ecd2787a43c94b5@changeid > > This makes UDL devices work on ChromeOS again after commit > > c91acda3a380 ("drm/gem: Check for valid formats"). Prior to that > > commit things were "working" because we'd silently treat the ARGB8888 > > that ChromeOS wanted as XRGB8888. > > This problem has been caused by userspace. Why can it not be fixed there? I guess the one argument I could make is that the kernel isn't supposed to break userspace. Before the extra format validation patch, AKA commit c91acda3a380 ("drm/gem: Check for valid formats"), userspace worked. Now it doesn't. That being said, one can certainly argue that userspace was working in the past simply due to relying on a bug. ...and in such a case fixing the bug in userspace is preferred. I don't personally know _how_ to fix userspace but it feels like it should be possible. > And udl is just one driver. Any other driver without ARGB8888, such as > simpledrm or ofdrm, would be affected. Do these work? It's the ChromeOS compositor. I can totally believe that those drivers don't work. In this case, though, those drivers aren't needed by a USB peripheral that someone might plug in. ;-) -Doug
