linux-kernel - Re: bringing back media/zoran driver

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Message-ID: <20190923083647.GB1599@Red>
Date:   Mon, 23 Sep 2019 10:36:47 +0200
From:   Corentin Labbe <clabbe.montjoie@...il.com>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     mjpeg-users@...ts.sourceforge.net, linux-media@...r.kernel.org,
        mchehab@...nel.org, laurent.pinchart@...asonboard.com,
        linux-kernel@...r.kernel.org
Subject: Re: bringing back media/zoran driver

On Mon, Sep 23, 2019 at 10:05:09AM +0200, Hans Verkuil wrote:
> On 9/21/19 7:03 PM, Corentin Labbe wrote:
> > hello
> > 
> > I am the owner of a zoran based DC10+ card.
> > I am in the need of using it since yesterday and I found that its driver was removed.
> > 
> > Reverting the removing patch made to a temporary working situation.
> > 
> > If I understand correctly, it was removed due to lack of vb2 convertion.
> > If I am able to do this vb2 conversion, does bring it back in mainline will be posssible ?
> > In that case I am ready to assume to be the maintainer if needed.
> 
> It would be nice to get it back. The conversion to vb2 is the main requirement, but in
> general this driver needed some TLC in general: it's a very old driver and the coding
> standards were quite a bit lower than they are today.
> 
> But the vb2 conversion is the most important part.
> 
> It's unfortunately not the easiest thing to do (if it was, we'd have done it already!),
> and it is also a 'big bang' patch, i.e. one very large patch that converts the driver
> to vb2. It's all or nothing, you can't have half a vb2 conversion, so that makes it hard
> to review.

Hello

Yes I started a bit to do it by using other conversion patch as helper and I saw this "one big step" problem.

> 
> The easiest way is to use the v4l2-compliance utility to verify the conversion. Running
> 'v4l2-compliance -s' is a good way of verifying this.
> 
> My recommended approach is to:
> 
> 1) first revert the removal patch (commit 8dce4b265a53)
> 2) clean up the coding style. Probably easiest to create one patch per source.
>    Use 'checkpatch.pl --strict -f <source>' for this. Doing this should make the
>    source code easier to understand/review.
> 3) Run v4l2-compliance (without the -s option) and fix any failures it finds.
> 4) Convert to vb2, using 'v4l2-compliance -s' to test.
> 
> Be aware that the code is messy compared to modern standards. Do not be afraid
> to create cleanup patches, it's probably needed.
> 
> The v4l2-compliance utility is part of https://git.linuxtv.org/v4l-utils.git/.
> See the README on how to build. Always use the v4l2-compliance version from this
> git repo since that's always the latest and greatest.
> 
> I recommend that you join the #v4l irc channel on freenode.org. Most core devs that
> can help with advice are there during office hours (and often outside of office hours
> as well). That's for the European timezones since most devs are based in Europe.
> 

Thanks, I has planned to ask this question about the priority between v4l2-compliance and vb2.

Regards