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. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
