dumb BOs and prime

[Daniel Stone]

Hi Rob,

On 4 December 2015 at 17:49, Rob Herring <robh at kernel.org> wrote:
> I'm working on getting Android working with DRM drivers. ATM, I'm
> using virtio-gpu as the driver and trying to get just KMS side working
> without rendering. I have it working with stock AOSP and the emulated
> fb with a few additions to the virtio-gpu driver[1]. Now I'm trying to
> get things working with native KMS using drm_gralloc and
> drm_hwcomposer (now in AOSP). I've hit one problem though which I'm
> not sure how to solve without hacking around it.
>
> Is prime allowed on dumb BOs? AIUI, dumb buffer allocation is not
> allowed on render nodes and drmPrimeHandleToFD is not allowed on
> card0, so I'm stuck. I could open both nodes, but then I want the case
> of no render node to work. After some searching, I thought it was a
> matter of needing to do drmAuthMagic, but then found that is
> considered obsolete[2].

drmPrimeHandleToFD definitely is allowed on card0; does the driver set
the DRIVER_PRIME cap, and have a prime_handle_to_fd hook?

Cheers,
Daniel