Hi All

This has been in the pipeline for a while, but I've finally cleaned
up our HEVC decoder driver to be in a shape to at least get a first
review.
John Cox has done almost all of the work under contract to Raspberry
Pi, and I'm largely just doing the process of patch curation and
sending.

There are a couple of questions raised in frameworks.
The main one is that the codec has 2 independent phases to the decode,
CABAC and reconstruction. To keep the decoder operating optimally
means that two requests need to be in process at once, whilst the
current frameworks don't want to allow as there is an implicit
assumption of only a single job being active at once, and
completition returns both buffers and releases the media request.

The OUTPUT queue buffer is finished with and can be returned at the
end of phase 1, but the media request is still required for phase 2.
The frameworks currently force the driver to be returning both
together via v4l2_m2m_buf_done_and_job_finish. v4l2_m2m_job_finish
would complete the job without returning the buffer as we need,
however if the driver has set VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF
then we have a WARN in v4l2_m2m_job_finish.
Dropping the WARN as this series is currently doing isn't going to be
the right answer, but it isn't obvious what the right answer is.
Discussion required.

We also have a need to hold on to the media request for phase 2. John
had discussed this with Ezequiel (and others) a couple of years back,
and hence suggested a patch that adds media_request_{pin,unpin} to
grab references on the media request. Discussion required on that
or a better way of handling it.

I will apologise in advance for sending this V1 just before I head off
on the Christmas break, but will respond to things as soon as possible.

Thanks
  Dave

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
Dave Stevenson (4):
      docs: uapi: media: Document Raspberry Pi NV12 column format
      media: ioctl: Add pixel formats NV12MT_COL128 and NV12MT_10_COL128
      media: dt-bindings: media: Add binding for the Raspberry Pi HEVC decoder
      arm: dts: bcm2711-rpi: Add HEVC decoder node

Ezequiel Garcia (1):
      RFC: media: Add media_request_{pin,unpin} API

John Cox (2):
      media: platform: Add Raspberry Pi HEVC decoder driver
      RFC: v4l2-mem2mem: Remove warning from v4l2_m2m_job_finish

 .../bindings/media/raspberrypi,hevc-dec.yaml       |   72 +
 .../userspace-api/media/v4l/pixfmt-yuv-planar.rst  |   42 +
 MAINTAINERS                                        |   10 +
 arch/arm/boot/dts/broadcom/bcm2711-rpi.dtsi        |    5 +
 arch/arm/boot/dts/broadcom/bcm2711.dtsi            |    9 +
 drivers/media/mc/mc-request.c                      |   35 +
 drivers/media/platform/raspberrypi/Kconfig         |    1 +
 drivers/media/platform/raspberrypi/Makefile        |    1 +
 .../media/platform/raspberrypi/hevc_dec/Kconfig    |   17 +
 .../media/platform/raspberrypi/hevc_dec/Makefile   |    5 +
 .../media/platform/raspberrypi/hevc_dec/hevc_d.c   |  443 ++++
 .../media/platform/raspberrypi/hevc_dec/hevc_d.h   |  190 ++
 .../platform/raspberrypi/hevc_dec/hevc_d_h265.c    | 2629 ++++++++++++++++++++
 .../platform/raspberrypi/hevc_dec/hevc_d_hw.c      |  376 +++
 .../platform/raspberrypi/hevc_dec/hevc_d_hw.h      |  303 +++
 .../platform/raspberrypi/hevc_dec/hevc_d_video.c   |  685 +++++
 .../platform/raspberrypi/hevc_dec/hevc_d_video.h   |   38 +
 drivers/media/v4l2-core/v4l2-ioctl.c               |    2 +
 drivers/media/v4l2-core/v4l2-mem2mem.c             |    7 -
 include/media/media-request.h                      |   12 +
 include/uapi/linux/videodev2.h                     |    5 +
 21 files changed, 4880 insertions(+), 7 deletions(-)
---
base-commit: e90c9612ac3969cb8206029a26bcd2b6f5d4a942
change-id: 20241212-media-rpi-hevc-dec-3b5be739f3bd

Best regards,
-- 
Dave Stevenson <dave.stevenson@raspberrypi.com>

Hi Dave,

Le vendredi 20 décembre 2024 à 16:21 +0000, Dave Stevenson a écrit :
> Hi All
> 
> This has been in the pipeline for a while, but I've finally cleaned
> up our HEVC decoder driver to be in a shape to at least get a first
> review.
> John Cox has done almost all of the work under contract to Raspberry
> Pi, and I'm largely just doing the process of patch curation and
> sending.
> 
> There are a couple of questions raised in frameworks.
> The main one is that the codec has 2 independent phases to the decode,
> CABAC and reconstruction. To keep the decoder operating optimally
> means that two requests need to be in process at once, whilst the
> current frameworks don't want to allow as there is an implicit
> assumption of only a single job being active at once, and
> completition returns both buffers and releases the media request.
> 
> The OUTPUT queue buffer is finished with and can be returned at the
> end of phase 1, but the media request is still required for phase 2.
> The frameworks currently force the driver to be returning both
> together via v4l2_m2m_buf_done_and_job_finish. v4l2_m2m_job_finish
> would complete the job without returning the buffer as we need,
> however if the driver has set VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF
> then we have a WARN in v4l2_m2m_job_finish.
> Dropping the WARN as this series is currently doing isn't going to be
> the right answer, but it isn't obvious what the right answer is.
> Discussion required.

I think part of the manual request completion RFC will be to evaluate the impact
on VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF feature. MTK does not support
interleaved interlaced decoding (only alternate), so they didn't have to
implement that feature.

Overall, It would be nice to get your feedback on the new manual request
proposal, which is I believe better then the pin/unpin API you have in this
serie.

> 
> We also have a need to hold on to the media request for phase 2. John
> had discussed this with Ezequiel (and others) a couple of years back,
> and hence suggested a patch that adds media_request_{pin,unpin} to
> grab references on the media request. Discussion required on that
> or a better way of handling it.
> 
> I will apologise in advance for sending this V1 just before I head off
> on the Christmas break, but will respond to things as soon as possible.

One thing missing in this summary is how this driver is being validated
(specially that for this one requires a downstream fork of FFMPEG). To this
report we ask for:

- v4l2-compliance results
- Fluster conformance tests results [1] and I believe you need [2]

[1] https://github.com/fluendo/fluster
[2] https://github.com/fluendo/fluster/pull/179

GStreamer support is there in main now, but without the needed software video
converter for you column tiling, we can't use it for that (i.e. only works
through GL or Wayland).

regards,
Nicolas

> 
> Thanks
>   Dave
> 
> Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> ---
> Dave Stevenson (4):
>       docs: uapi: media: Document Raspberry Pi NV12 column format
>       media: ioctl: Add pixel formats NV12MT_COL128 and NV12MT_10_COL128
>       media: dt-bindings: media: Add binding for the Raspberry Pi HEVC decoder
>       arm: dts: bcm2711-rpi: Add HEVC decoder node
> 
> Ezequiel Garcia (1):
>       RFC: media: Add media_request_{pin,unpin} API
> 
> John Cox (2):
>       media: platform: Add Raspberry Pi HEVC decoder driver
>       RFC: v4l2-mem2mem: Remove warning from v4l2_m2m_job_finish
> 
>  .../bindings/media/raspberrypi,hevc-dec.yaml       |   72 +
>  .../userspace-api/media/v4l/pixfmt-yuv-planar.rst  |   42 +
>  MAINTAINERS                                        |   10 +
>  arch/arm/boot/dts/broadcom/bcm2711-rpi.dtsi        |    5 +
>  arch/arm/boot/dts/broadcom/bcm2711.dtsi            |    9 +
>  drivers/media/mc/mc-request.c                      |   35 +
>  drivers/media/platform/raspberrypi/Kconfig         |    1 +
>  drivers/media/platform/raspberrypi/Makefile        |    1 +
>  .../media/platform/raspberrypi/hevc_dec/Kconfig    |   17 +
>  .../media/platform/raspberrypi/hevc_dec/Makefile   |    5 +
>  .../media/platform/raspberrypi/hevc_dec/hevc_d.c   |  443 ++++
>  .../media/platform/raspberrypi/hevc_dec/hevc_d.h   |  190 ++
>  .../platform/raspberrypi/hevc_dec/hevc_d_h265.c    | 2629 ++++++++++++++++++++
>  .../platform/raspberrypi/hevc_dec/hevc_d_hw.c      |  376 +++
>  .../platform/raspberrypi/hevc_dec/hevc_d_hw.h      |  303 +++
>  .../platform/raspberrypi/hevc_dec/hevc_d_video.c   |  685 +++++
>  .../platform/raspberrypi/hevc_dec/hevc_d_video.h   |   38 +
>  drivers/media/v4l2-core/v4l2-ioctl.c               |    2 +
>  drivers/media/v4l2-core/v4l2-mem2mem.c             |    7 -
>  include/media/media-request.h                      |   12 +
>  include/uapi/linux/videodev2.h                     |    5 +
>  21 files changed, 4880 insertions(+), 7 deletions(-)
> ---
> base-commit: e90c9612ac3969cb8206029a26bcd2b6f5d4a942
> change-id: 20241212-media-rpi-hevc-dec-3b5be739f3bd
> 
> Best regards,

On Mon, 06 Jan 2025 15:46:51 -0500, you wrote:

>Hi Dave,
>
>Le vendredi 20 décembre 2024 à 16:21 +0000, Dave Stevenson a écrit :
>> Hi All
>> 
>> This has been in the pipeline for a while, but I've finally cleaned
>> up our HEVC decoder driver to be in a shape to at least get a first
>> review.
>> John Cox has done almost all of the work under contract to Raspberry
>> Pi, and I'm largely just doing the process of patch curation and
>> sending.
>> 
>> There are a couple of questions raised in frameworks.
>> The main one is that the codec has 2 independent phases to the decode,
>> CABAC and reconstruction. To keep the decoder operating optimally
>> means that two requests need to be in process at once, whilst the
>> current frameworks don't want to allow as there is an implicit
>> assumption of only a single job being active at once, and
>> completition returns both buffers and releases the media request.
>> 
>> The OUTPUT queue buffer is finished with and can be returned at the
>> end of phase 1, but the media request is still required for phase 2.
>> The frameworks currently force the driver to be returning both
>> together via v4l2_m2m_buf_done_and_job_finish. v4l2_m2m_job_finish
>> would complete the job without returning the buffer as we need,
>> however if the driver has set VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF
>> then we have a WARN in v4l2_m2m_job_finish.
>> Dropping the WARN as this series is currently doing isn't going to be
>> the right answer, but it isn't obvious what the right answer is.
>> Discussion required.
>
>I think part of the manual request completion RFC will be to evaluate the impact
>on VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF feature. MTK does not support
>interleaved interlaced decoding (only alternate), so they didn't have to
>implement that feature.
>
>Overall, It would be nice to get your feedback on the new manual request
>proposal, which is I believe better then the pin/unpin API you have in this
>serie.

Is the effect of the manual complete API different from the pin API? Pin
incs the ref count on the media object to prevent competion,
manaul_complete sets a flag to do the same thing. Or have I missed the
point?

I don't mind what call is used as long as the effect is to be able to
delay media object completion. (In my first veraion of the code I
created a dummy object and attached it to the media object, when I
wanted to unpin I deleted the dummy object - pin was just a cleaner
API.)

The pin API is counted and needs no new structure elements (which is
nice), but manual_complete does give a flag that allows other functions
to know that holding on to the media object whilst releasing OUTPUT is
intentional so can be made to work cleanly with things like
v4l2_m2m_job_finish so is probably the better solution (assuming my
understand of how it works is correct). 

I'll try to build a version of the code using manual_complete in the
next few days.

Regards

JC

>> 
>> We also have a need to hold on to the media request for phase 2. John
>> had discussed this with Ezequiel (and others) a couple of years back,
>> and hence suggested a patch that adds media_request_{pin,unpin} to
>> grab references on the media request. Discussion required on that
>> or a better way of handling it.
>> 
>> I will apologise in advance for sending this V1 just before I head off
>> on the Christmas break, but will respond to things as soon as possible.
>
>One thing missing in this summary is how this driver is being validated
>(specially that for this one requires a downstream fork of FFMPEG). To this
>report we ask for:
>
>- v4l2-compliance results
>- Fluster conformance tests results [1] and I believe you need [2]
>
>[1] https://github.com/fluendo/fluster
>[2] https://github.com/fluendo/fluster/pull/179
>
>GStreamer support is there in main now, but without the needed software video
>converter for you column tiling, we can't use it for that (i.e. only works
>through GL or Wayland).
>
>regards,
>Nicolas
>
>> 
>> Thanks
>>   Dave
>> 
>> Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
>> ---
>> Dave Stevenson (4):
>>       docs: uapi: media: Document Raspberry Pi NV12 column format
>>       media: ioctl: Add pixel formats NV12MT_COL128 and NV12MT_10_COL128
>>       media: dt-bindings: media: Add binding for the Raspberry Pi HEVC decoder
>>       arm: dts: bcm2711-rpi: Add HEVC decoder node
>> 
>> Ezequiel Garcia (1):
>>       RFC: media: Add media_request_{pin,unpin} API
>> 
>> John Cox (2):
>>       media: platform: Add Raspberry Pi HEVC decoder driver
>>       RFC: v4l2-mem2mem: Remove warning from v4l2_m2m_job_finish
>> 
>>  .../bindings/media/raspberrypi,hevc-dec.yaml       |   72 +
>>  .../userspace-api/media/v4l/pixfmt-yuv-planar.rst  |   42 +
>>  MAINTAINERS                                        |   10 +
>>  arch/arm/boot/dts/broadcom/bcm2711-rpi.dtsi        |    5 +
>>  arch/arm/boot/dts/broadcom/bcm2711.dtsi            |    9 +
>>  drivers/media/mc/mc-request.c                      |   35 +
>>  drivers/media/platform/raspberrypi/Kconfig         |    1 +
>>  drivers/media/platform/raspberrypi/Makefile        |    1 +
>>  .../media/platform/raspberrypi/hevc_dec/Kconfig    |   17 +
>>  .../media/platform/raspberrypi/hevc_dec/Makefile   |    5 +
>>  .../media/platform/raspberrypi/hevc_dec/hevc_d.c   |  443 ++++
>>  .../media/platform/raspberrypi/hevc_dec/hevc_d.h   |  190 ++
>>  .../platform/raspberrypi/hevc_dec/hevc_d_h265.c    | 2629 ++++++++++++++++++++
>>  .../platform/raspberrypi/hevc_dec/hevc_d_hw.c      |  376 +++
>>  .../platform/raspberrypi/hevc_dec/hevc_d_hw.h      |  303 +++
>>  .../platform/raspberrypi/hevc_dec/hevc_d_video.c   |  685 +++++
>>  .../platform/raspberrypi/hevc_dec/hevc_d_video.h   |   38 +
>>  drivers/media/v4l2-core/v4l2-ioctl.c               |    2 +
>>  drivers/media/v4l2-core/v4l2-mem2mem.c             |    7 -
>>  include/media/media-request.h                      |   12 +
>>  include/uapi/linux/videodev2.h                     |    5 +
>>  21 files changed, 4880 insertions(+), 7 deletions(-)
>> ---
>> base-commit: e90c9612ac3969cb8206029a26bcd2b6f5d4a942
>> change-id: 20241212-media-rpi-hevc-dec-3b5be739f3bd
>> 
>> Best regards,

Hi John,

Le mercredi 08 janvier 2025 à 09:52 +0000, John Cox a écrit :
> On Mon, 06 Jan 2025 15:46:51 -0500, you wrote:
> 
> > Hi Dave,
> > 
> > Le vendredi 20 décembre 2024 à 16:21 +0000, Dave Stevenson a écrit :
> > > Hi All
> > > 
> > > This has been in the pipeline for a while, but I've finally cleaned
> > > up our HEVC decoder driver to be in a shape to at least get a first
> > > review.
> > > John Cox has done almost all of the work under contract to Raspberry
> > > Pi, and I'm largely just doing the process of patch curation and
> > > sending.
> > > 
> > > There are a couple of questions raised in frameworks.
> > > The main one is that the codec has 2 independent phases to the decode,
> > > CABAC and reconstruction. To keep the decoder operating optimally
> > > means that two requests need to be in process at once, whilst the
> > > current frameworks don't want to allow as there is an implicit
> > > assumption of only a single job being active at once, and
> > > completition returns both buffers and releases the media request.
> > > 
> > > The OUTPUT queue buffer is finished with and can be returned at the
> > > end of phase 1, but the media request is still required for phase 2.
> > > The frameworks currently force the driver to be returning both
> > > together via v4l2_m2m_buf_done_and_job_finish. v4l2_m2m_job_finish
> > > would complete the job without returning the buffer as we need,
> > > however if the driver has set VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF
> > > then we have a WARN in v4l2_m2m_job_finish.
> > > Dropping the WARN as this series is currently doing isn't going to be
> > > the right answer, but it isn't obvious what the right answer is.
> > > Discussion required.
> > 
> > I think part of the manual request completion RFC will be to evaluate the impact
> > on VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF feature. MTK does not support
> > interleaved interlaced decoding (only alternate), so they didn't have to
> > implement that feature.
> > 
> > Overall, It would be nice to get your feedback on the new manual request
> > proposal, which is I believe better then the pin/unpin API you have in this
> > serie.
> 
> Is the effect of the manual complete API different from the pin API? Pin
> incs the ref count on the media object to prevent competion,
> manaul_complete sets a flag to do the same thing. Or have I missed the
> point?

The request contains "objects", usually controls and a src buffer. The state of
the request goes to complete implicitly when the last object is removed. The
manual completion avoids adding ref-count on top of this, and simply disable the
implicit signalling of the request. With that we can signal everything in the
most logical order:

1. Program the register from controls -> mark controls complete
2. Entropy decode the stream -> mark src buffer done
3. Reconstruct the image -> mark dst buffer done
4. Signal the request completion

Before that, you always had to hold on the src buffer, and only mark it done
after the reconstruction was complete and the dst buffer was marked done. That
didn't matter for single function HW of course.

Unlike the pin/unpin, manual completion mode removes the implicit completion
bound to the fact the last "object" is removed from the request, and leave it to
the driver to decide when to actually signal the request. Internally, the give a
reference to the driver of course (similar to pin).

> 
> I don't mind what call is used as long as the effect is to be able to
> delay media object completion. (In my first veraion of the code I
> created a dummy object and attached it to the media object, when I
> wanted to unpin I deleted the dummy object - pin was just a cleaner
> API.)

The manual completion patchset is very similar really in you step back.

> 
> The pin API is counted and needs no new structure elements (which is
> nice), but manual_complete does give a flag that allows other functions
> to know that holding on to the media object whilst releasing OUTPUT is
> intentional so can be made to work cleanly with things like
> v4l2_m2m_job_finish so is probably the better solution (assuming my
> understand of how it works is correct). 
> 
> I'll try to build a version of the code using manual_complete in the
> next few days.

Thanks! your feedback will be very useful.

Nicolas

> 
> Regards
> 
> JC
> 
> > > 
> > > We also have a need to hold on to the media request for phase 2. John
> > > had discussed this with Ezequiel (and others) a couple of years back,
> > > and hence suggested a patch that adds media_request_{pin,unpin} to
> > > grab references on the media request. Discussion required on that
> > > or a better way of handling it.
> > > 
> > > I will apologise in advance for sending this V1 just before I head off
> > > on the Christmas break, but will respond to things as soon as possible.
> > 
> > One thing missing in this summary is how this driver is being validated
> > (specially that for this one requires a downstream fork of FFMPEG). To this
> > report we ask for:
> > 
> > - v4l2-compliance results
> > - Fluster conformance tests results [1] and I believe you need [2]
> > 
> > [1] https://github.com/fluendo/fluster
> > [2] https://github.com/fluendo/fluster/pull/179
> > 
> > GStreamer support is there in main now, but without the needed software video
> > converter for you column tiling, we can't use it for that (i.e. only works
> > through GL or Wayland).
> > 
> > regards,
> > Nicolas
> > 
> > > 
> > > Thanks
> > >   Dave
> > > 
> > > Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> > > ---
> > > Dave Stevenson (4):
> > >       docs: uapi: media: Document Raspberry Pi NV12 column format
> > >       media: ioctl: Add pixel formats NV12MT_COL128 and NV12MT_10_COL128
> > >       media: dt-bindings: media: Add binding for the Raspberry Pi HEVC decoder
> > >       arm: dts: bcm2711-rpi: Add HEVC decoder node
> > > 
> > > Ezequiel Garcia (1):
> > >       RFC: media: Add media_request_{pin,unpin} API
> > > 
> > > John Cox (2):
> > >       media: platform: Add Raspberry Pi HEVC decoder driver
> > >       RFC: v4l2-mem2mem: Remove warning from v4l2_m2m_job_finish
> > > 
> > >  .../bindings/media/raspberrypi,hevc-dec.yaml       |   72 +
> > >  .../userspace-api/media/v4l/pixfmt-yuv-planar.rst  |   42 +
> > >  MAINTAINERS                                        |   10 +
> > >  arch/arm/boot/dts/broadcom/bcm2711-rpi.dtsi        |    5 +
> > >  arch/arm/boot/dts/broadcom/bcm2711.dtsi            |    9 +
> > >  drivers/media/mc/mc-request.c                      |   35 +
> > >  drivers/media/platform/raspberrypi/Kconfig         |    1 +
> > >  drivers/media/platform/raspberrypi/Makefile        |    1 +
> > >  .../media/platform/raspberrypi/hevc_dec/Kconfig    |   17 +
> > >  .../media/platform/raspberrypi/hevc_dec/Makefile   |    5 +
> > >  .../media/platform/raspberrypi/hevc_dec/hevc_d.c   |  443 ++++
> > >  .../media/platform/raspberrypi/hevc_dec/hevc_d.h   |  190 ++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_h265.c    | 2629 ++++++++++++++++++++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_hw.c      |  376 +++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_hw.h      |  303 +++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_video.c   |  685 +++++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_video.h   |   38 +
> > >  drivers/media/v4l2-core/v4l2-ioctl.c               |    2 +
> > >  drivers/media/v4l2-core/v4l2-mem2mem.c             |    7 -
> > >  include/media/media-request.h                      |   12 +
> > >  include/uapi/linux/videodev2.h                     |    5 +
> > >  21 files changed, 4880 insertions(+), 7 deletions(-)
> > > ---
> > > base-commit: e90c9612ac3969cb8206029a26bcd2b6f5d4a942
> > > change-id: 20241212-media-rpi-hevc-dec-3b5be739f3bd
> > > 
> > > Best regards,

Hi Nicolas

On Mon, 6 Jan 2025 at 20:46, Nicolas Dufresne <nicolas@ndufresne.ca> wrote:
>
> Hi Dave,
>
> Le vendredi 20 décembre 2024 à 16:21 +0000, Dave Stevenson a écrit :
> > Hi All
> >
> > This has been in the pipeline for a while, but I've finally cleaned
> > up our HEVC decoder driver to be in a shape to at least get a first
> > review.
> > John Cox has done almost all of the work under contract to Raspberry
> > Pi, and I'm largely just doing the process of patch curation and
> > sending.
> >
> > There are a couple of questions raised in frameworks.
> > The main one is that the codec has 2 independent phases to the decode,
> > CABAC and reconstruction. To keep the decoder operating optimally
> > means that two requests need to be in process at once, whilst the
> > current frameworks don't want to allow as there is an implicit
> > assumption of only a single job being active at once, and
> > completition returns both buffers and releases the media request.
> >
> > The OUTPUT queue buffer is finished with and can be returned at the
> > end of phase 1, but the media request is still required for phase 2.
> > The frameworks currently force the driver to be returning both
> > together via v4l2_m2m_buf_done_and_job_finish. v4l2_m2m_job_finish
> > would complete the job without returning the buffer as we need,
> > however if the driver has set VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF
> > then we have a WARN in v4l2_m2m_job_finish.
> > Dropping the WARN as this series is currently doing isn't going to be
> > the right answer, but it isn't obvious what the right answer is.
> > Discussion required.
>
> I think part of the manual request completion RFC will be to evaluate the impact
> on VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF feature. MTK does not support
> interleaved interlaced decoding (only alternate), so they didn't have to
> implement that feature.
>
> Overall, It would be nice to get your feedback on the new manual request
> proposal, which is I believe better then the pin/unpin API you have in this
> serie.

I wasn't aware of that series, but I / John will take a look.

> >
> > We also have a need to hold on to the media request for phase 2. John
> > had discussed this with Ezequiel (and others) a couple of years back,
> > and hence suggested a patch that adds media_request_{pin,unpin} to
> > grab references on the media request. Discussion required on that
> > or a better way of handling it.
> >
> > I will apologise in advance for sending this V1 just before I head off
> > on the Christmas break, but will respond to things as soon as possible.
>
> One thing missing in this summary is how this driver is being validated
> (specially that for this one requires a downstream fork of FFMPEG). To this
> report we ask for:
>
> - v4l2-compliance results
> - Fluster conformance tests results [1] and I believe you need [2]
>
> [1] https://github.com/fluendo/fluster
> [2] https://github.com/fluendo/fluster/pull/179

Sure, I'll sort that before doing a V2.

> GStreamer support is there in main now, but without the needed software video
> converter for you column tiling, we can't use it for that (i.e. only works
> through GL or Wayland).

Can you point me at the right place for the software converter?
It's a relatively trivial reformat required to get it back into NV12 /
I420 or 10bit equivalents, so happy to do that. I think John already
has NEON optimised code if desired.

  Dave

> regards,
> Nicolas
>
> >
> > Thanks
> >   Dave
> >
> > Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> > ---
> > Dave Stevenson (4):
> >       docs: uapi: media: Document Raspberry Pi NV12 column format
> >       media: ioctl: Add pixel formats NV12MT_COL128 and NV12MT_10_COL128
> >       media: dt-bindings: media: Add binding for the Raspberry Pi HEVC decoder
> >       arm: dts: bcm2711-rpi: Add HEVC decoder node
> >
> > Ezequiel Garcia (1):
> >       RFC: media: Add media_request_{pin,unpin} API
> >
> > John Cox (2):
> >       media: platform: Add Raspberry Pi HEVC decoder driver
> >       RFC: v4l2-mem2mem: Remove warning from v4l2_m2m_job_finish
> >
> >  .../bindings/media/raspberrypi,hevc-dec.yaml       |   72 +
> >  .../userspace-api/media/v4l/pixfmt-yuv-planar.rst  |   42 +
> >  MAINTAINERS                                        |   10 +
> >  arch/arm/boot/dts/broadcom/bcm2711-rpi.dtsi        |    5 +
> >  arch/arm/boot/dts/broadcom/bcm2711.dtsi            |    9 +
> >  drivers/media/mc/mc-request.c                      |   35 +
> >  drivers/media/platform/raspberrypi/Kconfig         |    1 +
> >  drivers/media/platform/raspberrypi/Makefile        |    1 +
> >  .../media/platform/raspberrypi/hevc_dec/Kconfig    |   17 +
> >  .../media/platform/raspberrypi/hevc_dec/Makefile   |    5 +
> >  .../media/platform/raspberrypi/hevc_dec/hevc_d.c   |  443 ++++
> >  .../media/platform/raspberrypi/hevc_dec/hevc_d.h   |  190 ++
> >  .../platform/raspberrypi/hevc_dec/hevc_d_h265.c    | 2629 ++++++++++++++++++++
> >  .../platform/raspberrypi/hevc_dec/hevc_d_hw.c      |  376 +++
> >  .../platform/raspberrypi/hevc_dec/hevc_d_hw.h      |  303 +++
> >  .../platform/raspberrypi/hevc_dec/hevc_d_video.c   |  685 +++++
> >  .../platform/raspberrypi/hevc_dec/hevc_d_video.h   |   38 +
> >  drivers/media/v4l2-core/v4l2-ioctl.c               |    2 +
> >  drivers/media/v4l2-core/v4l2-mem2mem.c             |    7 -
> >  include/media/media-request.h                      |   12 +
> >  include/uapi/linux/videodev2.h                     |    5 +
> >  21 files changed, 4880 insertions(+), 7 deletions(-)
> > ---
> > base-commit: e90c9612ac3969cb8206029a26bcd2b6f5d4a942
> > change-id: 20241212-media-rpi-hevc-dec-3b5be739f3bd
> >
> > Best regards,
>

Le mardi 07 janvier 2025 à 16:13 +0000, Dave Stevenson a écrit :
> Hi Nicolas
> 
> On Mon, 6 Jan 2025 at 20:46, Nicolas Dufresne <nicolas@ndufresne.ca> wrote:
> > 
> > Hi Dave,
> > 
> > Le vendredi 20 décembre 2024 à 16:21 +0000, Dave Stevenson a écrit :
> > > Hi All
> > > 
> > > This has been in the pipeline for a while, but I've finally cleaned
> > > up our HEVC decoder driver to be in a shape to at least get a first
> > > review.
> > > John Cox has done almost all of the work under contract to Raspberry
> > > Pi, and I'm largely just doing the process of patch curation and
> > > sending.
> > > 
> > > There are a couple of questions raised in frameworks.
> > > The main one is that the codec has 2 independent phases to the decode,
> > > CABAC and reconstruction. To keep the decoder operating optimally
> > > means that two requests need to be in process at once, whilst the
> > > current frameworks don't want to allow as there is an implicit
> > > assumption of only a single job being active at once, and
> > > completition returns both buffers and releases the media request.
> > > 
> > > The OUTPUT queue buffer is finished with and can be returned at the
> > > end of phase 1, but the media request is still required for phase 2.
> > > The frameworks currently force the driver to be returning both
> > > together via v4l2_m2m_buf_done_and_job_finish. v4l2_m2m_job_finish
> > > would complete the job without returning the buffer as we need,
> > > however if the driver has set VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF
> > > then we have a WARN in v4l2_m2m_job_finish.
> > > Dropping the WARN as this series is currently doing isn't going to be
> > > the right answer, but it isn't obvious what the right answer is.
> > > Discussion required.
> > 
> > I think part of the manual request completion RFC will be to evaluate the impact
> > on VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF feature. MTK does not support
> > interleaved interlaced decoding (only alternate), so they didn't have to
> > implement that feature.
> > 
> > Overall, It would be nice to get your feedback on the new manual request
> > proposal, which is I believe better then the pin/unpin API you have in this
> > serie.
> 
> I wasn't aware of that series, but I / John will take a look.
> 
> > > 
> > > We also have a need to hold on to the media request for phase 2. John
> > > had discussed this with Ezequiel (and others) a couple of years back,
> > > and hence suggested a patch that adds media_request_{pin,unpin} to
> > > grab references on the media request. Discussion required on that
> > > or a better way of handling it.
> > > 
> > > I will apologise in advance for sending this V1 just before I head off
> > > on the Christmas break, but will respond to things as soon as possible.
> > 
> > One thing missing in this summary is how this driver is being validated
> > (specially that for this one requires a downstream fork of FFMPEG). To this
> > report we ask for:
> > 
> > - v4l2-compliance results
> > - Fluster conformance tests results [1] and I believe you need [2]
> > 
> > [1] https://github.com/fluendo/fluster
> > [2] https://github.com/fluendo/fluster/pull/179
> 
> Sure, I'll sort that before doing a V2.
> 
> > GStreamer support is there in main now, but without the needed software video
> > converter for you column tiling, we can't use it for that (i.e. only works
> > through GL or Wayland).
> 
> Can you point me at the right place for the software converter?
> It's a relatively trivial reformat required to get it back into NV12 /
> I420 or 10bit equivalents, so happy to do that. I think John already
> has NEON optimised code if desired.

Its challenging in the way its implemented in GStreamer Video library. Basically
all formats needs its GstVideoFormatInfo structure to be filled in the static
table, and then minimally a slow path for color conversion, which is reduced to
pack/unpack of a single line of video data. With tiled (or column format) the
notion of line is not as obvious.

https://gitlab.freedesktop.org/gstreamer/gstreamer/-/blob/main/subprojects/gst-plugins-base/gst-libs/gst/video/video-format.c

For tile format with fixed dimensions, we have extra information for the tile
layout (GstVideoTileInfo), but we didn't think about full height tiles when that
was added. This information is needed to generically crop images, which is why
its so complicated.

One option we could use to make it fit as a tiled format is to introduce a new
GstVideoTileMode GST_VIDEO_TILE_MODE_COLUMN. Then we set the tiled height to
match the usual HW height step, making it so you have 128 x step tiles, laid out
in column. Alternatively, we can start with a step of 1 (which will make the
slow path a lot slower then needed), and later add an optimization for the
column layout, so it handle full columns.

If you manage to find a good step size, then all you will have to implement is
the backend for gst_video_tile_get_index(), the rest of the slow path will be
generic.

Fast path are possible, with ORC (a cross platform byte code language that can
be JIT into SIMD instructions), but I don't currently see much use for "fast",
since the GPU pretty much always accepts these buffers, so the software path
remains a neat debugging tool and allow conformance testing.

Nicolas

> 
>   Dave
> 
> > regards,
> > Nicolas
> > 
> > > 
> > > Thanks
> > >   Dave
> > > 
> > > Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> > > ---
> > > Dave Stevenson (4):
> > >       docs: uapi: media: Document Raspberry Pi NV12 column format
> > >       media: ioctl: Add pixel formats NV12MT_COL128 and NV12MT_10_COL128
> > >       media: dt-bindings: media: Add binding for the Raspberry Pi HEVC decoder
> > >       arm: dts: bcm2711-rpi: Add HEVC decoder node
> > > 
> > > Ezequiel Garcia (1):
> > >       RFC: media: Add media_request_{pin,unpin} API
> > > 
> > > John Cox (2):
> > >       media: platform: Add Raspberry Pi HEVC decoder driver
> > >       RFC: v4l2-mem2mem: Remove warning from v4l2_m2m_job_finish
> > > 
> > >  .../bindings/media/raspberrypi,hevc-dec.yaml       |   72 +
> > >  .../userspace-api/media/v4l/pixfmt-yuv-planar.rst  |   42 +
> > >  MAINTAINERS                                        |   10 +
> > >  arch/arm/boot/dts/broadcom/bcm2711-rpi.dtsi        |    5 +
> > >  arch/arm/boot/dts/broadcom/bcm2711.dtsi            |    9 +
> > >  drivers/media/mc/mc-request.c                      |   35 +
> > >  drivers/media/platform/raspberrypi/Kconfig         |    1 +
> > >  drivers/media/platform/raspberrypi/Makefile        |    1 +
> > >  .../media/platform/raspberrypi/hevc_dec/Kconfig    |   17 +
> > >  .../media/platform/raspberrypi/hevc_dec/Makefile   |    5 +
> > >  .../media/platform/raspberrypi/hevc_dec/hevc_d.c   |  443 ++++
> > >  .../media/platform/raspberrypi/hevc_dec/hevc_d.h   |  190 ++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_h265.c    | 2629 ++++++++++++++++++++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_hw.c      |  376 +++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_hw.h      |  303 +++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_video.c   |  685 +++++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_video.h   |   38 +
> > >  drivers/media/v4l2-core/v4l2-ioctl.c               |    2 +
> > >  drivers/media/v4l2-core/v4l2-mem2mem.c             |    7 -
> > >  include/media/media-request.h                      |   12 +
> > >  include/uapi/linux/videodev2.h                     |    5 +
> > >  21 files changed, 4880 insertions(+), 7 deletions(-)
> > > ---
> > > base-commit: e90c9612ac3969cb8206029a26bcd2b6f5d4a942
> > > change-id: 20241212-media-rpi-hevc-dec-3b5be739f3bd
> > > 
> > > Best regards,
> > 

On Tue, 7 Jan 2025 at 16:13, Dave Stevenson
<dave.stevenson@raspberrypi.com> wrote:
>
> Hi Nicolas
>
> On Mon, 6 Jan 2025 at 20:46, Nicolas Dufresne <nicolas@ndufresne.ca> wrote:
> >
> > Hi Dave,
> >
> > Le vendredi 20 décembre 2024 à 16:21 +0000, Dave Stevenson a écrit :
> > > Hi All
> > >
> > > This has been in the pipeline for a while, but I've finally cleaned
> > > up our HEVC decoder driver to be in a shape to at least get a first
> > > review.
> > > John Cox has done almost all of the work under contract to Raspberry
> > > Pi, and I'm largely just doing the process of patch curation and
> > > sending.
> > >
> > > There are a couple of questions raised in frameworks.
> > > The main one is that the codec has 2 independent phases to the decode,
> > > CABAC and reconstruction. To keep the decoder operating optimally
> > > means that two requests need to be in process at once, whilst the
> > > current frameworks don't want to allow as there is an implicit
> > > assumption of only a single job being active at once, and
> > > completition returns both buffers and releases the media request.
> > >
> > > The OUTPUT queue buffer is finished with and can be returned at the
> > > end of phase 1, but the media request is still required for phase 2.
> > > The frameworks currently force the driver to be returning both
> > > together via v4l2_m2m_buf_done_and_job_finish. v4l2_m2m_job_finish
> > > would complete the job without returning the buffer as we need,
> > > however if the driver has set VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF
> > > then we have a WARN in v4l2_m2m_job_finish.
> > > Dropping the WARN as this series is currently doing isn't going to be
> > > the right answer, but it isn't obvious what the right answer is.
> > > Discussion required.
> >
> > I think part of the manual request completion RFC will be to evaluate the impact
> > on VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF feature. MTK does not support
> > interleaved interlaced decoding (only alternate), so they didn't have to
> > implement that feature.
> >
> > Overall, It would be nice to get your feedback on the new manual request
> > proposal, which is I believe better then the pin/unpin API you have in this
> > serie.
>
> I wasn't aware of that series, but I / John will take a look.

As I said at the beginning, I'm largely an intermediary here, and may
get things wrong as my codec knowledge is far from comprehensive. I'm
hoping John will correct me if I misrepresent our conversations.

As you say the MTK codec doesn't set
VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF, and hence it can call
v4l2_m2m_job_finish without hitting the WARN.

Your comment about it not supporting interleaved interlaced decoding
confuses me slightly. Almost all the codecs allow a single frame to be
encoded as multiple slices, and I'd be surprised if none of the test
streams exercise that.
Our reading of the situation was that if you have more than one
encoded slice making up the video frame then you are NOT obliged to
submit all of the slices at once via the variable length array
control, and submitting the slices one at a time is permitted. That
means that almost all decoders have to set the
VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF flag to be able to hold onto
the CAPTURE buffer until it has been given all the encoded data to
generate it.

If there isn't a need to support a multi-slice frame being presented
via multiple OUTPUT buffers, then we can cull some code and drop the
flag.
HEVC has no real concept of interlaced content, so no need to worry
about that as the other route to having multiple slices producing one
video frame.

  Dave

> > >
> > > We also have a need to hold on to the media request for phase 2. John
> > > had discussed this with Ezequiel (and others) a couple of years back,
> > > and hence suggested a patch that adds media_request_{pin,unpin} to
> > > grab references on the media request. Discussion required on that
> > > or a better way of handling it.
> > >
> > > I will apologise in advance for sending this V1 just before I head off
> > > on the Christmas break, but will respond to things as soon as possible.
> >
> > One thing missing in this summary is how this driver is being validated
> > (specially that for this one requires a downstream fork of FFMPEG). To this
> > report we ask for:
> >
> > - v4l2-compliance results
> > - Fluster conformance tests results [1] and I believe you need [2]
> >
> > [1] https://github.com/fluendo/fluster
> > [2] https://github.com/fluendo/fluster/pull/179
>
> Sure, I'll sort that before doing a V2.
>
> > GStreamer support is there in main now, but without the needed software video
> > converter for you column tiling, we can't use it for that (i.e. only works
> > through GL or Wayland).
>
> Can you point me at the right place for the software converter?
> It's a relatively trivial reformat required to get it back into NV12 /
> I420 or 10bit equivalents, so happy to do that. I think John already
> has NEON optimised code if desired.
>
>   Dave
>
> > regards,
> > Nicolas
> >
> > >
> > > Thanks
> > >   Dave
> > >
> > > Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> > > ---
> > > Dave Stevenson (4):
> > >       docs: uapi: media: Document Raspberry Pi NV12 column format
> > >       media: ioctl: Add pixel formats NV12MT_COL128 and NV12MT_10_COL128
> > >       media: dt-bindings: media: Add binding for the Raspberry Pi HEVC decoder
> > >       arm: dts: bcm2711-rpi: Add HEVC decoder node
> > >
> > > Ezequiel Garcia (1):
> > >       RFC: media: Add media_request_{pin,unpin} API
> > >
> > > John Cox (2):
> > >       media: platform: Add Raspberry Pi HEVC decoder driver
> > >       RFC: v4l2-mem2mem: Remove warning from v4l2_m2m_job_finish
> > >
> > >  .../bindings/media/raspberrypi,hevc-dec.yaml       |   72 +
> > >  .../userspace-api/media/v4l/pixfmt-yuv-planar.rst  |   42 +
> > >  MAINTAINERS                                        |   10 +
> > >  arch/arm/boot/dts/broadcom/bcm2711-rpi.dtsi        |    5 +
> > >  arch/arm/boot/dts/broadcom/bcm2711.dtsi            |    9 +
> > >  drivers/media/mc/mc-request.c                      |   35 +
> > >  drivers/media/platform/raspberrypi/Kconfig         |    1 +
> > >  drivers/media/platform/raspberrypi/Makefile        |    1 +
> > >  .../media/platform/raspberrypi/hevc_dec/Kconfig    |   17 +
> > >  .../media/platform/raspberrypi/hevc_dec/Makefile   |    5 +
> > >  .../media/platform/raspberrypi/hevc_dec/hevc_d.c   |  443 ++++
> > >  .../media/platform/raspberrypi/hevc_dec/hevc_d.h   |  190 ++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_h265.c    | 2629 ++++++++++++++++++++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_hw.c      |  376 +++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_hw.h      |  303 +++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_video.c   |  685 +++++
> > >  .../platform/raspberrypi/hevc_dec/hevc_d_video.h   |   38 +
> > >  drivers/media/v4l2-core/v4l2-ioctl.c               |    2 +
> > >  drivers/media/v4l2-core/v4l2-mem2mem.c             |    7 -
> > >  include/media/media-request.h                      |   12 +
> > >  include/uapi/linux/videodev2.h                     |    5 +
> > >  21 files changed, 4880 insertions(+), 7 deletions(-)
> > > ---
> > > base-commit: e90c9612ac3969cb8206029a26bcd2b6f5d4a942
> > > change-id: 20241212-media-rpi-hevc-dec-3b5be739f3bd
> > >
> > > Best regards,
> >

Hi Dave,

Le mardi 07 janvier 2025 à 17:36 +0000, Dave Stevenson a écrit :
> On Tue, 7 Jan 2025 at 16:13, Dave Stevenson
> <dave.stevenson@raspberrypi.com> wrote:
> > 
> > Hi Nicolas
> > 
> > On Mon, 6 Jan 2025 at 20:46, Nicolas Dufresne <nicolas@ndufresne.ca> wrote:
> > > 
> > > Hi Dave,
> > > 
> > > Le vendredi 20 décembre 2024 à 16:21 +0000, Dave Stevenson a écrit :
> > > > Hi All
> > > > 
> > > > This has been in the pipeline for a while, but I've finally cleaned
> > > > up our HEVC decoder driver to be in a shape to at least get a first
> > > > review.
> > > > John Cox has done almost all of the work under contract to Raspberry
> > > > Pi, and I'm largely just doing the process of patch curation and
> > > > sending.
> > > > 
> > > > There are a couple of questions raised in frameworks.
> > > > The main one is that the codec has 2 independent phases to the decode,
> > > > CABAC and reconstruction. To keep the decoder operating optimally
> > > > means that two requests need to be in process at once, whilst the
> > > > current frameworks don't want to allow as there is an implicit
> > > > assumption of only a single job being active at once, and
> > > > completition returns both buffers and releases the media request.
> > > > 
> > > > The OUTPUT queue buffer is finished with and can be returned at the
> > > > end of phase 1, but the media request is still required for phase 2.
> > > > The frameworks currently force the driver to be returning both
> > > > together via v4l2_m2m_buf_done_and_job_finish. v4l2_m2m_job_finish
> > > > would complete the job without returning the buffer as we need,
> > > > however if the driver has set VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF
> > > > then we have a WARN in v4l2_m2m_job_finish.
> > > > Dropping the WARN as this series is currently doing isn't going to be
> > > > the right answer, but it isn't obvious what the right answer is.
> > > > Discussion required.
> > > 
> > > I think part of the manual request completion RFC will be to evaluate the impact
> > > on VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF feature. MTK does not support
> > > interleaved interlaced decoding (only alternate), so they didn't have to
> > > implement that feature.
> > > 
> > > Overall, It would be nice to get your feedback on the new manual request
> > > proposal, which is I believe better then the pin/unpin API you have in this
> > > serie.
> > 
> > I wasn't aware of that series, but I / John will take a look.
> 
> As I said at the beginning, I'm largely an intermediary here, and may
> get things wrong as my codec knowledge is far from comprehensive. I'm
> hoping John will correct me if I misrepresent our conversations.
> 
> As you say the MTK codec doesn't set
> VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF, and hence it can call
> v4l2_m2m_job_finish without hitting the WARN.
> 
> Your comment about it not supporting interleaved interlaced decoding
> confuses me slightly. Almost all the codecs allow a single frame to be
> encoded as multiple slices, and I'd be surprised if none of the test
> streams exercise that.

MTK VCODEC is a frame based HEVC decoder. All slices are passed within the same
request (up to 600). Upstream, only Cedrus driver is slice based, though for
large number of slices this has performance issues (even though you gain on
latency).

> Our reading of the situation was that if you have more than one
> encoded slice making up the video frame then you are NOT obliged to
> submit all of the slices at once via the variable length array
> control, and submitting the slices one at a time is permitted. That
> means that almost all decoders have to set the
> VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF flag to be able to hold onto
> the CAPTURE buffer until it has been given all the encoded data to
> generate it.

We don't have support for that, a new v4l2_stateless_hevc_decode_mode would be
required. Here's what the spec says:


    * - ``V4L2_STATELESS_HEVC_DECODE_MODE_SLICE_BASED``
      - 0
      - Decoding is done at the slice granularity.
        The OUTPUT buffer must contain a **single** slice.
    * - ``V4L2_STATELESS_HEVC_DECODE_MODE_FRAME_BASED``
      - 1
      - Decoding is done at the frame granularity.
        The OUTPUT buffer must contain **all** slices needed to decode the
        frame.

So one, or all. Additionally, (and doc could be improved here),
V4L2_CID_STATELESS_HEVC_SLICE_PARAMS is strictly required for SLICED_BASED, and
must contain 1 slice. While for the second, some drivers needs it, some don't,
userspace needs to check if the control is present or not.

SLICE_BASED depends on VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF, otherwise you
can't queue capture buffers ahead of time, and loose in throughput. So a new
DYN_SLICE_BASED (with some proper name), would also require it.
VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF is also needed when you need to decode
top and bottom field in the same capture buffer, hence my reference to that (MTK
chromebook firmware don't support that for any codecs).

You could also ignore all this, and implement
V4L2_STATELESS_HEVC_DECODE_MODE_FRAME_BASED on top of your slice based decoder.
No latency gain, but you also no longer need
VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF which let you postpone adding new
helpers to complete the job when this feature is used. Yet, I think the manual
request completion proposal would be a lot better if we had that issue covered.

> 
> If there isn't a need to support a multi-slice frame being presented
> via multiple OUTPUT buffers, then we can cull some code and drop the
> flag.

> HEVC has no real concept of interlaced content, so no need to worry
> about that as the other route to having multiple slices producing one
> video frame.

I've seen non-tiled decoders that internally double the stride, and offset the
same buffer by one line for the second field, to generate interleaved data, but
as you said, this is the exception rather then the rule. :-)

p.s. your understanding is pretty accurate

> 
>   Dave
> 
> > > > 
> > > > We also have a need to hold on to the media request for phase 2. John
> > > > had discussed this with Ezequiel (and others) a couple of years back,
> > > > and hence suggested a patch that adds media_request_{pin,unpin} to
> > > > grab references on the media request. Discussion required on that
> > > > or a better way of handling it.
> > > > 
> > > > I will apologise in advance for sending this V1 just before I head off
> > > > on the Christmas break, but will respond to things as soon as possible.
> > > 
> > > One thing missing in this summary is how this driver is being validated
> > > (specially that for this one requires a downstream fork of FFMPEG). To this
> > > report we ask for:
> > > 
> > > - v4l2-compliance results
> > > - Fluster conformance tests results [1] and I believe you need [2]
> > > 
> > > [1] https://github.com/fluendo/fluster
> > > [2] https://github.com/fluendo/fluster/pull/179
> > 
> > Sure, I'll sort that before doing a V2.
> > 
> > > GStreamer support is there in main now, but without the needed software video
> > > converter for you column tiling, we can't use it for that (i.e. only works
> > > through GL or Wayland).
> > 
> > Can you point me at the right place for the software converter?
> > It's a relatively trivial reformat required to get it back into NV12 /
> > I420 or 10bit equivalents, so happy to do that. I think John already
> > has NEON optimised code if desired.
> > 
> >   Dave
> > 
> > > regards,
> > > Nicolas
> > > 
> > > > 
> > > > Thanks
> > > >   Dave
> > > > 
> > > > Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> > > > ---
> > > > Dave Stevenson (4):
> > > >       docs: uapi: media: Document Raspberry Pi NV12 column format
> > > >       media: ioctl: Add pixel formats NV12MT_COL128 and NV12MT_10_COL128
> > > >       media: dt-bindings: media: Add binding for the Raspberry Pi HEVC decoder
> > > >       arm: dts: bcm2711-rpi: Add HEVC decoder node
> > > > 
> > > > Ezequiel Garcia (1):
> > > >       RFC: media: Add media_request_{pin,unpin} API
> > > > 
> > > > John Cox (2):
> > > >       media: platform: Add Raspberry Pi HEVC decoder driver
> > > >       RFC: v4l2-mem2mem: Remove warning from v4l2_m2m_job_finish
> > > > 
> > > >  .../bindings/media/raspberrypi,hevc-dec.yaml       |   72 +
> > > >  .../userspace-api/media/v4l/pixfmt-yuv-planar.rst  |   42 +
> > > >  MAINTAINERS                                        |   10 +
> > > >  arch/arm/boot/dts/broadcom/bcm2711-rpi.dtsi        |    5 +
> > > >  arch/arm/boot/dts/broadcom/bcm2711.dtsi            |    9 +
> > > >  drivers/media/mc/mc-request.c                      |   35 +
> > > >  drivers/media/platform/raspberrypi/Kconfig         |    1 +
> > > >  drivers/media/platform/raspberrypi/Makefile        |    1 +
> > > >  .../media/platform/raspberrypi/hevc_dec/Kconfig    |   17 +
> > > >  .../media/platform/raspberrypi/hevc_dec/Makefile   |    5 +
> > > >  .../media/platform/raspberrypi/hevc_dec/hevc_d.c   |  443 ++++
> > > >  .../media/platform/raspberrypi/hevc_dec/hevc_d.h   |  190 ++
> > > >  .../platform/raspberrypi/hevc_dec/hevc_d_h265.c    | 2629 ++++++++++++++++++++
> > > >  .../platform/raspberrypi/hevc_dec/hevc_d_hw.c      |  376 +++
> > > >  .../platform/raspberrypi/hevc_dec/hevc_d_hw.h      |  303 +++
> > > >  .../platform/raspberrypi/hevc_dec/hevc_d_video.c   |  685 +++++
> > > >  .../platform/raspberrypi/hevc_dec/hevc_d_video.h   |   38 +
> > > >  drivers/media/v4l2-core/v4l2-ioctl.c               |    2 +
> > > >  drivers/media/v4l2-core/v4l2-mem2mem.c             |    7 -
> > > >  include/media/media-request.h                      |   12 +
> > > >  include/uapi/linux/videodev2.h                     |    5 +
> > > >  21 files changed, 4880 insertions(+), 7 deletions(-)
> > > > ---
> > > > base-commit: e90c9612ac3969cb8206029a26bcd2b6f5d4a942
> > > > change-id: 20241212-media-rpi-hevc-dec-3b5be739f3bd
> > > > 
> > > > Best regards,
> > >