linux-kernel - Re: [PATCH v4] media: Driver for Toshiba et8ek8 5MP sensor

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Date:   Thu, 3 Nov 2016 09:14:33 +0100
From:   Pavel Machek <pavel@....cz>
To:     Sakari Ailus <sakari.ailus@....fi>
Cc:     ivo.g.dimitrov.75@...il.com, sre@...nel.org, pali.rohar@...il.com,
        linux-media@...r.kernel.org, galak@...eaurora.org,
        mchehab@....samsung.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] media: Driver for Toshiba et8ek8 5MP sensor

Hi!

> > > > I'll have to go through the patches, et8ek8 driver is probably not
> > > > enough to get useful video. platform/video-bus-switch.c is needed for
> > > > camera switching, then some omap3isp patches to bind flash and
> > > > autofocus into the subdevice.
> > > > 
> > > > Then, device tree support on n900 can be added.
> > > 
> > > I briefly discussed with with Sebastian.
> > > 
> > > Do you think the elusive support for the secondary camera is worth keeping
> > > out the main camera from the DT in mainline? As long as there's a reasonable
> > > way to get it working, I'd just merge that. If someone ever gets the
> > > secondary camera working properly and nicely with the video bus switch,
> > > that's cool, we'll somehow deal with the problem then. But frankly I don't
> > > think it's very useful even if we get there: the quality is really
> > > bad.
> > 
> > Well, I am a little bit worried that /dev/video* entries will
> > renumber themself when the the front camera support is merged,
> > breaking userspace.
> > 
> > But the first step is still the same: get et8ek8 support merged :-).
> 
> Do you happen to have a patch for the DT part as well? People could more
> easily test this...

If you want complete/working tree for testing, it is at

https://git.kernel.org/cgit/linux/kernel/git/pavel/linux-n900.git/?h=camera-v4.9

If you want userspace to go with that, there's fcam-dev. It is on
gitlab:

https://gitlab.com/pavelm/fcam-dev


> > > > > Do all the modes work for you currently btw.?
> > > > 
> > > > I don't think I got 5MP mode to work. Even 2.5MP mode is tricky (needs
> > > > a lot of continuous memory).
> > > 
> > > The OMAP 3 ISP has got an MMU, getting some contiguous memory is not really
> > > a problem when you have a 4 GiB empty space to use.
> > 
> > Ok, maybe it is something else. 2.5MP mode seems to work better when
> > there is free memory.
> 
> That's very odd. Do you use MMAP or USERPTR buffers btw.? I remember the
> cache was different on 3430, that could be an issue as well (VIVT AFAIR, so
> flushing requires making sure there are no other mappings or flushing the
> entire cache).

The userland code I'm using does

 struct v4l2_requestbuffers req;
 memset(&req, 0, sizeof(req));
 req.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 req.memory = V4L2_MEMORY_MMAP;
 req.count  = 8;
 printf("Reqbufs\n");
 if (ioctl(fd, VIDIOC_REQBUFS, &req) < 0) {
 ...
		

so I guess answer to your question is "MMAP". The v4l interface is at

https://gitlab.com/pavelm/fcam-dev/blob/master/src/N900/V4L2Sensor.cpp

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

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