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From: Daniel Stone <daniel@fooishbar.org>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Christopher James Halse Rogers
	<christopher.halse.rogers@canonical.com>,
	dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 1/2] drm: Add DRM_CAP_PRIME_SCANOUT.
Date: Tue, 4 Apr 2017 11:11:42 +0100	[thread overview]
Message-ID: <CAPj87rP_TSeD+xCKD4F7pPRY=fCxx+r55dSCPtgFV5zDLJWy_A@mail.gmail.com> (raw)
In-Reply-To: <20170404083112.s5rp7bwhj3jimoxi@phenom.ffwll.local>

Hi,

On 4 April 2017 at 09:31, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Tue, Apr 04, 2017 at 06:13:20PM +1000, raof@ubuntu.com wrote:
>> Until recently, on (at least) nouveau, radeon, and amdgpu attempting to scanout of an
>> imported dma-buf would silently result in the dma-buf sharing being broken.
>>
>> While the hardware is capable of scanning out of imported dma-bufs (at least in some circumstances),
>> these drivers do not currently implement it, so attempts to scan out of such buffers will never succeed.
>>
>> Add a userspace-visible drm capability and associated driver_feature so that userspace can discover
>> when scanning out of an imported dma-buf can work.
>>
>> Signed-off-by: Christopher James Halse Rogers <christopher.halse.rogers@canonical.com>
>
> This seems like an awful specific special case. Why can't you do the
> entire dance upfront, i.e. import buffer, addfb2? None of that has any
> visible effect, and it will also allow you to check runtime constraints
> which can't be covered with this here.

Oh, that already happens. Chris sent out a series which fixes bugs for
PRIME import across a few drivers, mostly ones which need to pin
scanout buffers to dedicated memory. So this cap is basically
DRM_CAP_PRIME_SCANOUT_ISNT_BUGGY. FWIW, I'm fairly skeptical about
adding caps which essentially declare the absence of bugs like this.

Cheers,
Daniel
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  reply	other threads:[~2017-04-04 10:11 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-04  8:13 [PATCH] Tell userspace if scanning out of an imported PRIME buffer is safe raof
2017-04-04  8:13 ` [PATCH 1/2] drm: Add DRM_CAP_PRIME_SCANOUT raof
2017-04-04  8:31   ` Daniel Vetter
2017-04-04 10:11     ` Daniel Stone [this message]
2017-04-04 10:27     ` Christopher James Halse Rogers
2017-04-04 10:43       ` Lucas Stach
2017-04-04 11:53         ` Daniel Vetter
2017-04-05  0:20           ` Christopher James Halse Rogers
2017-04-05  6:27             ` Daniel Vetter
2017-04-05  6:52               ` Christopher James Halse Rogers
2017-04-05  8:15             ` Lucas Stach
2017-04-05  9:59               ` Daniel Vetter
2017-04-05 10:14                 ` Lucas Stach
2017-04-05 11:13                   ` Christopher James Halse Rogers
2017-04-05 11:21                     ` Christian König
2017-04-10  8:52                       ` Michel Dänzer
2017-04-10  9:03                         ` Christian König
2017-04-10 14:10                           ` Alex Deucher
2017-04-06  7:47                   ` Christopher James Halse Rogers
2017-04-10  8:51                     ` Michel Dänzer
2017-04-17  5:05                       ` Christopher James Halse Rogers
2017-04-17  6:41                         ` Michel Dänzer
2017-04-04 10:43       ` Daniel Stone
2017-04-04 11:15         ` Christian König
2017-04-04 11:32           ` Daniel Stone
2017-04-04 11:43             ` Christian König
2017-04-04  8:13 ` [PATCH 2/2] drm/i915: support DRIVER_PRIME_SCANOUT raof

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