Re: [PATCH v3 0/2] media: cedrus: Add H264 decoding support

From: Tomasz Figa <tfiga@chromium.org>
To: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Hans Verkuil <hans.verkuil@cisco.com>,
	Alexandre Courbot <acourbot@chromium.org>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Pawel Osciak <posciak@chromium.org>,
	Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
	Chen-Yu Tsai <wens@csie.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
	Joerg Roedel <joro@8bytes.org>,"
	<linux-arm-kernel@lists.infradead.org>,
	Linux Media Mailing List <linux-media@vger.kernel.org>,
	Nicolas Dufresne <nicolas.dufresne@collabora.com>,
	jenskuske@gmail.com, Jernej Skrabec <jernej.skrabec@gmail.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	Ezequiel Garcia <ezequiel@collabora.com>,
	linux-sunxi@googlegroups.com,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH v3 0/2] media: cedrus: Add H264 decoding support
Date: Tue, 12 Feb 2019 21:50:18 +0900	[thread overview]
Message-ID: <CAAFQd5AcqiwAb30ajLxmj6LZoabVygUsAB8A+drpityOAvY60A@mail.gmail.com> (raw)
In-Reply-To: <cover.d3bb4d93da91ed5668025354ee1fca656e7d5b8b.1549895062.git-series.maxime.ripard@bootlin.com>

Hi Maxime,

On Mon, Feb 11, 2019 at 11:39 PM Maxime Ripard
<maxime.ripard@bootlin.com> wrote:
>
> Hi,
>
> Here is a new version of the H264 decoding support in the cedrus
> driver.

Thanks for working on this. Please see my comments below.

>
> As you might already know, the cedrus driver relies on the Request
> API, and is a reverse engineered driver for the video decoding engine
> found on the Allwinner SoCs.
>
> This work has been possible thanks to the work done by the people
> behind libvdpau-sunxi found here:
> https://github.com/linux-sunxi/libvdpau-sunxi/
>
> I've tested the various ABI using this gdb script:
> http://code.bulix.org/jl4se4-505620?raw
>
> And this test script:
> http://code.bulix.org/8zle4s-505623?raw
>
> The application compiled is quite trivial:
> http://code.bulix.org/e34zp8-505624?raw
>
> The output is:
> arm:    builds/arm-test-v4l2-h264-structures
>         SHA1: 88cbf7485ba81831fc3b93772b215599b3b38318
> x86:    builds/x86-test-v4l2-h264-structures
>         SHA1: 88cbf7485ba81831fc3b93772b215599b3b38318
> x64:    builds/x64-test-v4l2-h264-structures
>         SHA1: 88cbf7485ba81831fc3b93772b215599b3b38318
> arm64:  builds/arm64-test-v4l2-h264-structures
>         SHA1: 88cbf7485ba81831fc3b93772b215599b3b38318
>
> Let me know if there's any flaw using that test setup, or if you have
> any comments on the patches.
>
> Maxime
>
> Changes from v2:
>   - Simplified _cedrus_write_ref_list as suggested by Jernej
>   - Set whether the frame is used as reference using nal_ref_idc
>   - Respect chroma_format_idc
>   - Fixes for the scaling list and prediction tables
>   - Wrote the documentation for the flags
>   - Added a bunch of defines to the driver bit fields
>   - Reworded the controls and data format descriptions as suggested
>     by Hans
>   - Reworked the controls' structure field size to avoid padding
>   - Removed the long term reference flag

This and...

>   - Reintroduced the neighbor info buffer
>   - Removed the ref_pic_list_p0/b0/b1 arrays that are redundant with the
>     one in the DPB

these are used in our Rockchip VDEC driver.

Could you elaborate on the reasons why they got removed?

Best regards,
Tomasz