linux-kernel - Re: [PATCH v9 5/9] media: platform: Add Cedrus VPU decoder driver

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Date:   Fri, 7 Sep 2018 16:25:28 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     Paul Kocialkowski <contact@...lk.fr>, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devel@...verdev.osuosl.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Chen-Yu Tsai <wens@...e.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        linux-sunxi@...glegroups.com, Randy Li <ayaka@...lik.info>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Alexandre Courbot <acourbot@...omium.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH v9 5/9] media: platform: Add Cedrus VPU decoder driver

On Fri, Sep 07, 2018 at 03:52:00PM +0200, Hans Verkuil wrote:
> On 09/07/2018 03:26 PM, Maxime Ripard wrote:
> > Hi Hans,
> > 
> > On Fri, Sep 07, 2018 at 03:13:19PM +0200, Hans Verkuil wrote:
> >> On 09/07/2018 12:24 AM, Paul Kocialkowski wrote:
> >>> From: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> >>>
> >>> This introduces the Cedrus VPU driver that supports the VPU found in
> >>> Allwinner SoCs, also known as Video Engine. It is implemented through
> >>> a V4L2 M2M decoder device and a media device (used for media requests).
> >>> So far, it only supports MPEG-2 decoding.
> >>>
> >>> Since this VPU is stateless, synchronization with media requests is
> >>> required in order to ensure consistency between frame headers that
> >>> contain metadata about the frame to process and the raw slice data that
> >>> is used to generate the frame.
> >>>
> >>> This driver was made possible thanks to the long-standing effort
> >>> carried out by the linux-sunxi community in the interest of reverse
> >>> engineering, documenting and implementing support for the Allwinner VPU.
> >>>
> >>> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> >>> Acked-by: Maxime Ripard <maxime.ripard@...tlin.com>
> >>
> >> One high-level comment:
> >>
> >> Can you add a TODO file for this staging driver? This can be done in
> >> a follow-up patch.
> >>
> >> It should contain what needs to be done to get this out of staging:
> >>
> >> - Request API needs to stabilize
> >> - Userspace support for stateless codecs must be created
> > 
> > On that particular note, as part of the effort to develop the driver,
> > we've also developped two userspace components:
> > 
> >   - v4l2-request-test, that has a bunch of sample frames for various
> >     codecs and will rely solely on the kernel request api (and DRM for
> >     the display part) to test and bringup a particular driver
> >     https://github.com/bootlin/v4l2-request-test
> > 
> >   - libva-v4l2-request, that is a libva implementation using the
> >     request API
> >     https://github.com/bootlin/libva-v4l2-request
> > 
> > Did you have something else in mind?
> 
> Reviewing this will be the next step. I haven't looked at the userspace components
> at all yet, so I don't know yet whether it is what we expect/want/need.

We meant this as a debug tool and a stop-gap measure, respectively, so
it might not be what you're expecting, and I'm kind of expecting to
have the libva fade away with media frameworks getting native support.

> I think this might be a very good topic for the media summit in October if we
> can get all the stakeholders together.

I'll be there, so we can definitely discuss this.

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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