On Tue, Sep 4, 2018 at 4:00 AM, Michel Dänzer <michel@xxxxxxxxxxx> wrote: > On 2018-09-03 7:07 p.m., Ilia Mirkin wrote: >> On Mon, Sep 3, 2018 at 12:45 PM, Daniel Vetter <daniel@xxxxxxxx> wrote: >>> On Mon, Sep 03, 2018 at 12:57:54PM +0200, Gerd Hoffmann wrote: >>>> Userspace on big endian machhines typically expects the ADDFB ioctl >>>> returns a big endian framebuffer. drm_mode_addfb() will call >>>> drm_mode_addfb2() unconditionally with little endian DRM_FORMAT_* >>>> values though, which is wrong. This patch fixes that. >>>> >>>> Drivers (both kernel and xorg) have quirks in place to deal with the >>>> broken drm_mode_addfb() behavior. Because of this we can't just change >>>> drm_mode_addfb() behavior for everybody without breaking things. So add >>>> a new driver feature flag DRIVER_PREFER_HOST_BYTE_ORDER, so drivers can >>>> opt-in. >>>> >>>> Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx> >>>> --- >>>> include/drm/drm_drv.h | 1 + >>>> drivers/gpu/drm/drm_framebuffer.c | 11 +++++++++++ >>>> 2 files changed, 12 insertions(+) >>>> >>>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h >>>> index 46a8009784..9cf12596cd 100644 >>>> --- a/include/drm/drm_drv.h >>>> +++ b/include/drm/drm_drv.h >>>> @@ -57,6 +57,7 @@ struct drm_printer; >>>> #define DRIVER_KMS_LEGACY_CONTEXT 0x20000 >>>> #define DRIVER_SYNCOBJ 0x40000 >>>> #define DRIVER_PREFER_XBGR_30BPP 0x80000 >>>> +#define DRIVER_PREFER_HOST_BYTE_ORDER 0x100000 >>> >>> Hm, not a huge fan of using driver_flags for random little quirks. I think >>> a boolean in sturct drm_mode_config would be much better. Bonus if you >>> also move the 30bpp hack over to that. Something like >>> mode_config.quirk_addfb_host_byte_order and >>> mode_config.quirk_addfb_prefer_xbgr_30bpp or whatever. That has the upside >>> of giving us a really nice place to put a huge comment about what this is >>> supposed to do. >>> >>> I think otherwise this looks overall rather reasonable. I think the only >>> other driver that ever cared about big endian was radeon/amdgpu. Would be >>> good to get at least an ack from amd folks, or a "meh, stopped caring". >> >> and nouveau. >> >> I do believe that ADDFB should be made to always prefer host byte >> order -- this is how all of the existing implementations work in >> practice. However e.g. nouveau wants DRM_FORMAT_XRGB8888. But it still >> treats it as host byte order. This will become more important in a >> world where ADDFB2 is more common. >> >> So, I think that this change should be applied, drivers (I suspect >> just nouveau and radeon) fixed up to consume the "new" formats, [...] > > As explained before, that would break radeon userspace on big endian hosts. We last discussed this about a year ago, so I hope you'll forgive my lapse in memory... There's userspace that uses ADDFB2 with DRM_FORMAT_XRGB8888 but expects it to be host-endian? If so, that'll be a problem for nouveau as well... -ilia _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
