On Tue, Sep 4, 2018 at 11:02 AM, Michel Dänzer <michel@xxxxxxxxxxx> wrote: > On 2018-09-04 3:05 p.m., Ilia Mirkin wrote: >> 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? > > ADDFB, not ADDFB2. The latter probably didn't even exist yet when this > was made to work. :) Right, but ADDFB doesn't know or care about DRM_FORMAT_*. That's what I'm saying -- keep ADDFB working, and fix up the DRM_FORMAT_* underneath it both in the conversion and in the driver. Gerd's patch allows us to do this incrementally, eventually truing up the DRM_FORMAT_* in the driver, enabling ADDFB2 to work as expected. -ilia _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
