On 3 August 2018 at 20:50, Sean Paul <seanpaul@xxxxxxxxxxxx> wrote: > On Fri, Aug 03, 2018 at 06:03:50PM +0100, Emil Velikov wrote: >> On 3 August 2018 at 16:06, Martin Fuzzey <martin.fuzzey@flowbird.group> wrote: >> > Hi Emil, >> > >> > On 03/08/18 14:35, Emil Velikov wrote: >> >> >> >> Hi Martin, >> >> >> >> On 1 August 2018 at 15:24, Martin Fuzzey <martin.fuzzey@flowbird.group> >> >> wrote: >> >> >> >> Let's start with the not-so obvious question: >> >> Why does one open the imx as render node? >> >> >> >> Of the top of my head: >> >> There is nothing in egl/android that should require an authenticated >> >> device. >> >> Hence, using a card node should be fine - the etnaviv code opens the >> >> render node it needs. >> > >> > >> > Yes, the problem is not in egl/android but in the scanout buffer allocation >> > code. >> > >> > etnaviv opens the render node on the *GPU* (for submitting GPU commands), >> > that part is fine. >> > >> > But scanout buffers need to be allocated from imx-drm not etnaviv. >> > >> > This done by renderonly_create_kms_dumb_buffer_for_resource() >> > [src/gallium/auxiliary/renderonly/renderonly.c] >> > Which uses DRM_IOCTL_MODE_CREATE_DUMB followed by >> > DRM_IOCTL_PRIME_FD_TO_HANDLE >> > on the "kms_fd" (probably poorly named because it's not actually used for >> > modesetting) >> > see imx_drm_screen_create()[ src/gallium/winsys/imx/drm/imx_drm_winsys.c] >> > >> > >> > If the card node is used DRM_IOCTL_MODE_CREATE_DUMB works but >> > DRM_IOCTL_PRIME_FD_TO_HANDLE fails, because the permissions are >> > DRM_AUTH|DRM_UNLOCKED|DRM_RENDER_ALLOW >> > >> Right I missed the DRM_AUTH, in the fd <> handle IOCTLs. >> So in order for things to work, we'd need to either: >> - allow dumb buffers for render nodes, or >> - drop the DRM_AUTH for fd <> handle imports >> >> Pointing an alternative solution, for kernel developers to analyse and >> make a decision. >> >> > >> > In android 8.1 the hardware composer runs in a seperate process and it has >> > to use the card node and be drm master (to use the KMS API), >> > therefore, when the surface flinger calls >> > renderonly_create_kms_dumb_buffer_for_resource() it is not authenticated. >> > >> > Making surface flinger use a render node fixes the problem for >> > DRM_IOCTL_PRIME_FD_TO_HANDLE (because that already has DRM_RENDER_ALLOW), >> > but DRM_IOCTL_MODE_CREATE_DUMB now fails without the patch. >> > >> > >> > This probably worked in previous versions of Android where surface flinger >> > and hwc were all in the same process. >> > >> There has been varying hacks for Android through the years. Bringing >> details into the discussion will result in a significant diversion. >> Something we could avoid, for the time being ;-) > > Did someone say diversion?!? The way this was handled prior to using > render/control nodes in drm_hwc/[drm/gbm]_gralloc is that all modesetting was > done via gralloc which was master. The hwc implementation was basically a proxy > backchanneling all of the work to gralloc. > > Anyways, we probably don't want to go back there. > Now that we got the diversion out of the way, any input on my proposal to drop the DRM_AUTH for fd <> imports. Am I missing something pretty obvious that makes the idea a no-go? Thanks Emil _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
