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
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.
Regards,
Martin
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