linux-kernel - Re: support autofocus / autogain in libv4l2

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Message-ID: <20170426105356.GB857@amd>
Date:   Wed, 26 Apr 2017 12:53:56 +0200
From:   Pavel Machek <pavel@....cz>
To:     Nicolas Dufresne <nicolas@...fresne.ca>
Cc:     Mauro Carvalho Chehab <mchehab@...pensource.com>,
        pali.rohar@...il.com, sre@...nel.org,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, tony@...mide.com, khilman@...nel.org,
        aaro.koskinen@....fi, ivo.g.dimitrov.75@...il.com,
        patrikbachan@...il.com, serge@...lyn.com, abcloriens@...il.com,
        Sakari Ailus <sakari.ailus@....fi>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-media@...r.kernel.org
Subject: Re: support autofocus / autogain in libv4l2

On Tue 2017-04-25 12:53:27, Nicolas Dufresne wrote:
> Le mardi 25 avril 2017 à 10:05 +0200, Pavel Machek a écrit :
> > Well, fd's are hard, because application can do fork() and now
> > interesting stuff happens. Threads are tricky, because now you have
> > locking etc.
> > 
> > libv4l2 is designed to be LD_PRELOADED. That is not really feasible
> > with "complex" library.
> 
> That is incorrect. The library propose an API where you simply replace
> certain low level calls, like ioctl -> v4l2_ioctl, open -> v4l2_open().
> You have to do that explicitly in your existing code. It does not
> abstract the API itself unlike libdrm.

You are right, no LD_PRELOAD. But same API as kernel, which is really
limiting -- see my other mail.

									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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