[PATCH 1/2] drm: Add DRM_CAP_PRIME_SCANOUT.

[Daniel Stone]

Hi,

On 4 April 2017 at 12:15, Christian König <deathsimple at vodafone.de> wrote:
> Am 04.04.2017 um 12:43 schrieb Daniel Stone:
>> Yeah, the ABI is that AddFB2 should fail hard on something which can
>> never be used as a framebuffer. The fact it didn't is a bug rather
>> than a behavioural change per se ...
>
> I agree on that, but the problem Christopher tries to solve looks a bit
> different from my perspective.
>
> He wants to know if a driver can scan out from a foreign BO or if he needs
> to copy the content.
>
> The problem I see with this patch is that the kernel doesn't look like the
> right place for this decision to make.

Any number of constraints exist there: 'can I use any completely
arbitrary dmabuf from anywhere?' doesn't express the full range. AddFB
can fail for other totally legitimate reasons, so to me it makes the
most sense to centralise the checks there.

Cheers,
Daniel