DRM/V4L2 buffer sharing (was: Re: Patches submitted via linux-media ML that are at patchwork.linuxtv.org)

DRM/V4L2 buffer sharing (was: Re: Patches submitted via linux-media ML that are at patchwork.linuxtv.org)

[Sylwester Nawrocki]

Hi Laurent,

On 08/15/2012 11:09 PM, Laurent Pinchart wrote:
> On Wednesday 15 August 2012 18:13:19 Sylwester Nawrocki wrote:
>> On 08/15/2012 12:06 AM, Laurent Pinchart wrote:
>>> On Tuesday 14 August 2012 18:37:23 Sylwester Nawrocki wrote:
>>>> On 08/14/2012 03:04 PM, Mauro Carvalho Chehab wrote:
>>>>> This one requires more testing:
>>>>>
>>>>> May,15 2012: [GIT,PULL,FOR,3.5] DMABUF importer feature in V4L2 API
>>>>>            http://patchwork.linuxtv.org/patch/11268  Sylwester Nawrocki
>>>>> <s.nawrocki@samsung.com>
>>>>
>>>> Hmm, this is not valid any more. Tomasz just posted a new patch series
>>>> that adds DMABUF importer and exporter feature altogether.
>>>>
>>>> [PATCHv8 00/26] Integration of videobuf2 with DMABUF
>>>>
>>>> I guess we need someone else to submit test patches for other H/W than
>>>> just Samsung SoCs. I'm not sure if we've got enough resources to port
>>>> this to other hardware. We have been using these features internally for
>>>> some time already. It's been 2 kernel releases and I can see only Ack
>>>> tags from Laurent on Tomasz's patch series, hence it seems there is no
>>>> wide interest in DMABUF support in V4L2 and this patch series is probably
>>>> going to stay in a fridge for another few kernel releases.
>>>
>>> What would be required to push it to v3.7 ?
>>
>> Mauro requested more test coverage on that, which is understood since this
>> is a fairly important API enhancement and the V4L2 video overlay API
>> replacement.
>>
>> We need DMABUF support added at some webcam driver and a DRM driver with
>> prime support (or some V4L2 output driver), I guess it would be best to
>> have that in a PC environment. It looks like i915/radeon/nouveau drivers
>> already have prime support.
> 
> uvcvideo has recently been moved to videobuf2, using vb2_vmalloc. I can easily
> test that, except that I have no idea how to export buffers on the i915 side
> when X is running. Have you looked into that ?

All right. Yes, I'm also not sure yet how to do it. I tried it on a laptop 
with i915 driver, but in the running system drmModeGetResources() just fails 
with EPERM. I've CCed dri-devel, so hopefully someone can shed some light
on this.

>> The DRM driver could be an exporter of buffers that would be passed to the
>> webcam driver.
>>
>> And except the kernel patches we would need a test application, similar
>> to that one:
>> http://git.infradead.org/users/kmpark/public-apps/blob/a7e755629a74a7ac13788
>> 2032a0f7b2480fa1490:/v4l2-drm-example/dmabuf-sharing.c
>>
>> I haven't been closely following the DMABUF APIs development, I think
>> Tomasz could provide more details on that.
>>
>> It's likely I'll get around and prepare a test case as outlined above in
>> coming days. Anyway, it would be appreciated if someone else could give this
>> patch series a try.
> 
> I've previously tested the patches on Renesas hardware, exporting buffers on
> the FBDEV side and importing them on the V4L2 side. We thus have test results
> for two different platforms, albeit all ARM-based.

I guess ARM is where those APIs will be used mostly, still it would be helpful
to have easier reproducible test environment.

--

Thanks,
Sylwester

Re: DRM/V4L2 buffer sharing

[Mauro Carvalho Chehab]

Em 17-08-2012 18:01, Sylwester Nawrocki escreveu:
> Hi Laurent,
> 
> On 08/15/2012 11:09 PM, Laurent Pinchart wrote:
>> On Wednesday 15 August 2012 18:13:19 Sylwester Nawrocki wrote:
>>> On 08/15/2012 12:06 AM, Laurent Pinchart wrote:
>>>> On Tuesday 14 August 2012 18:37:23 Sylwester Nawrocki wrote:
>>>>> On 08/14/2012 03:04 PM, Mauro Carvalho Chehab wrote:
>>>>>> This one requires more testing:
>>>>>>
>>>>>> May,15 2012: [GIT,PULL,FOR,3.5] DMABUF importer feature in V4L2 API
>>>>>>            http://patchwork.linuxtv.org/patch/11268  Sylwester Nawrocki
>>>>>> <s.nawrocki@samsung.com>
>>>>>
>>>>> Hmm, this is not valid any more. Tomasz just posted a new patch series
>>>>> that adds DMABUF importer and exporter feature altogether.
>>>>>
>>>>> [PATCHv8 00/26] Integration of videobuf2 with DMABUF
>>>>>
>>>>> I guess we need someone else to submit test patches for other H/W than
>>>>> just Samsung SoCs. I'm not sure if we've got enough resources to port
>>>>> this to other hardware. We have been using these features internally for
>>>>> some time already. It's been 2 kernel releases and I can see only Ack
>>>>> tags from Laurent on Tomasz's patch series, hence it seems there is no
>>>>> wide interest in DMABUF support in V4L2 and this patch series is probably
>>>>> going to stay in a fridge for another few kernel releases.
>>>>
>>>> What would be required to push it to v3.7 ?
>>>
>>> Mauro requested more test coverage on that, which is understood since this
>>> is a fairly important API enhancement and the V4L2 video overlay API
>>> replacement.
>>>
>>> We need DMABUF support added at some webcam driver and a DRM driver with
>>> prime support (or some V4L2 output driver), I guess it would be best to
>>> have that in a PC environment. It looks like i915/radeon/nouveau drivers
>>> already have prime support.
>>
>> uvcvideo has recently been moved to videobuf2, using vb2_vmalloc. I can easily
>> test that, except that I have no idea how to export buffers on the i915 side
>> when X is running. Have you looked into that ?
> 
> All right. Yes, I'm also not sure yet how to do it. I tried it on a laptop 
> with i915 driver, but in the running system drmModeGetResources() just fails 
> with EPERM. I've CCed dri-devel, so hopefully someone can shed some light
> on this.

Likely, you need to run with root permission to use it, or to write an Xorg
driver.

It is probably easier to get the V4L driver there, that uses the VIDIOC_OVERLAY
stuff, and make it work via DMABUF:
	http://cgit.freedesktop.org/xorg/driver/xf86-video-v4l/

In order to test it, xawtv has already the code needed to talk with the v4l
plugin.

What the plugin does is to export the video board as a XV extension, accessible
via xawtv. It currently talks with the display card also via XV, but I believe it
won't be hard to port it to work with DMABUF.

As the interface between xawtv and the v4l plugin is just Xv, changing the code
there from VIDIOC_OVERLAY to DMABUF should be trivial.

Regards,
Mauro

Re: DRM/V4L2 buffer sharing

[Laurent Pinchart]

Hi Mauro,

On Friday 17 August 2012 19:03:47 Mauro Carvalho Chehab wrote:
> Em 17-08-2012 18:01, Sylwester Nawrocki escreveu:
> > On 08/15/2012 11:09 PM, Laurent Pinchart wrote:
> >> On Wednesday 15 August 2012 18:13:19 Sylwester Nawrocki wrote:
> >>> On 08/15/2012 12:06 AM, Laurent Pinchart wrote:
> >>>> On Tuesday 14 August 2012 18:37:23 Sylwester Nawrocki wrote:
> >>>>> On 08/14/2012 03:04 PM, Mauro Carvalho Chehab wrote:
> >>>>>> This one requires more testing:
> >>>>>> 
> >>>>>> May,15 2012: [GIT,PULL,FOR,3.5] DMABUF importer feature in V4L2 API
> >>>>>> 
> >>>>>>            http://patchwork.linuxtv.org/patch/11268  Sylwester
> >>>>>>            Nawrocki
> >>>>>> 
> >>>>>> <s.nawrocki@samsung.com>
> >>>>> 
> >>>>> Hmm, this is not valid any more. Tomasz just posted a new patch series
> >>>>> that adds DMABUF importer and exporter feature altogether.
> >>>>> 
> >>>>> [PATCHv8 00/26] Integration of videobuf2 with DMABUF
> >>>>> 
> >>>>> I guess we need someone else to submit test patches for other H/W than
> >>>>> just Samsung SoCs. I'm not sure if we've got enough resources to port
> >>>>> this to other hardware. We have been using these features internally
> >>>>> for some time already. It's been 2 kernel releases and I can see only
> >>>>> Ack tags from Laurent on Tomasz's patch series, hence it seems there
> >>>>> is no wide interest in DMABUF support in V4L2 and this patch series is
> >>>>> probably going to stay in a fridge for another few kernel releases.
> >>>> 
> >>>> What would be required to push it to v3.7 ?
> >>> 
> >>> Mauro requested more test coverage on that, which is understood since
> >>> this is a fairly important API enhancement and the V4L2 video overlay
> >>> API replacement.
> >>> 
> >>> We need DMABUF support added at some webcam driver and a DRM driver with
> >>> prime support (or some V4L2 output driver), I guess it would be best to
> >>> have that in a PC environment. It looks like i915/radeon/nouveau drivers
> >>> already have prime support.
> >> 
> >> uvcvideo has recently been moved to videobuf2, using vb2_vmalloc. I can
> >> easily test that, except that I have no idea how to export buffers on
> >> the i915 side when X is running. Have you looked into that ?
> > 
> > All right. Yes, I'm also not sure yet how to do it. I tried it on a laptop
> > with i915 driver, but in the running system drmModeGetResources() just
> > fails with EPERM. I've CCed dri-devel, so hopefully someone can shed some
> > light on this.
> 
> Likely, you need to run with root permission to use it, or to write an Xorg
> driver.
> 
> It is probably easier to get the V4L driver there, that uses the
> VIDIOC_OVERLAY stuff, and make it work via DMABUF:
> 	http://cgit.freedesktop.org/xorg/driver/xf86-video-v4l/

That won't really help for our test cases. I want to capture from a UVC device 
using DMABUF import directly to the i915 DRM device using DRM export. In order 
to do so I will need to get hold of GEM objects that I can use to display the 
data, possibly through the OpenGL API. I'm looking for help on that last 
point, I can easily handle the UVC capture code myself.

> In order to test it, xawtv has already the code needed to talk with the v4l
> plugin.
> 
> What the plugin does is to export the video board as a XV extension,
> accessible via xawtv. It currently talks with the display card also via XV,
> but I believe it won't be hard to port it to work with DMABUF.
> 
> As the interface between xawtv and the v4l plugin is just Xv, changing the
> code there from VIDIOC_OVERLAY to DMABUF should be trivial.

-- 
Regards,

Laurent Pinchart