On Sat 2017-03-11 23:14:56, Russell King - ARM Linux wrote: > On Sat, Mar 11, 2017 at 08:25:49AM -0300, Mauro Carvalho Chehab wrote: > > This situation is there since 2009. If I remember well, you tried to write > > such generic plugin in the past, but never finished it, apparently because > > it is too complex. Others tried too over the years. > > > > The last trial was done by Jacek, trying to cover just the exynos4 driver. > > Yet, even such limited scope plugin was not good enough, as it was never > > merged upstream. Currently, there's no such plugins upstream. > > > > If we can't even merge a plugin that solves it for just *one* driver, > > I have no hope that we'll be able to do it for the generic case. > > This is what really worries me right now about the current proposal for > iMX6. What's being proposed is to make the driver exclusively MC-based. > > What that means is that existing applications are _not_ going to work > until we have some answer for libv4l2, and from what you've said above, > it seems that this has been attempted multiple times over the last _8_ > years, and each time it's failed. Yeah. We need a mid-layer between legacy applications and MC devices. Such layer does not exist in userspace or in kernel. > Loading the problem onto the user in the hope that the user knows > enough to properly configure it also doesn't work - who is going to > educate the user about the various quirks of the hardware they're > dealing with? We have docs. Users can write shell scripts. Still, mid-layer would be nice. > So, the problem space we have here is absolutely huge, and merely > having a plugin that activates when you open a /dev/video* node > really doesn't solve it. > > All in all, I really don't think "lets hope someone writes a v4l2 > plugin to solve it" is ever going to be successful. I don't even > see that there will ever be a userspace application that is anything > more than a representation of the dot graphs that users can use to > manually configure the capture system with system knowledge. > > I think everyone needs to take a step back and think long and hard > about this from the system usability perspective - I seriously > doubt that we will ever see any kind of solution to this if we > continue to progress with "we'll sort it in userspace some day." Mid-layer is difficult... there are _hundreds_ of possible pipeline setups. If it should live in kernel or in userspace is a question... but I don't think having it in kernel helps in any way. 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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