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, and then made to be the one-and-only way for ADDFB to function. That way we'll no longer be lying about the DRM_FORMAT being used. Cheers, -ilia _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
