RE: [RFC v2 2/7] media: rc: Add cec protocol handling

From: Kamil Debski <k.debski@samsung.com>
To: 'Bastien Nocera' <hadess@hadess.net>
Cc: 'Mauro Carvalho Chehab' <mchehab@osg.samsung.com>,
	dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	hverkuil@xs4all.nl, kyungmin.park@samsung.com,
	thomas@tommie-lie.de, sean@mess.org, linux-input@vger.kernel.org
Subject: RE: [RFC v2 2/7] media: rc: Add cec protocol handling
Date: Tue, 10 Mar 2015 16:40:13 +0100	[thread overview]
Message-ID: <002e01d05b48$80c19e90$8244dbb0$%debski@samsung.com> (raw)
In-Reply-To: <1425996895.11726.3.camel@hadess.net>

From: Bastien Nocera [mailto:hadess@hadess.net]
Sent: Tuesday, March 10, 2015 3:15 PM
> 
> On Tue, 2015-03-10 at 13:02 +0100, Kamil Debski wrote:
> > Hi Bastien,
> >
> > From: Bastien Nocera [mailto:hadess@hadess.net]
> > Sent: Monday, March 09, 2015 5:44 PM
> > >
> > > On Mon, 2015-03-09 at 17:22 +0100, Kamil Debski wrote:
> > > > Hi Mauro,
> > > >
> > > > From: Mauro Carvalho Chehab [mailto:mchehab@osg.samsung.com]
> > > > Sent: Sunday, March 08, 2015 3:21 PM
> > > >
> > > > > Em Thu, 22 Jan 2015 17:04:34 +0100 Kamil Debski
> > > > > <k.debski@samsung.com> escreveu:
> > > > >
> > > > > (c/c linux-input ML)
> > > > >
> > > > > > Add cec protocol handling the RC framework.
> > > > >
> > > > > I added some comments, that reflects my understanding from
> > > > > what's there at the keymap definitions found at:
> > > > >         http://xtreamerdev.googlecode.com/files/CEC_Specs.pdf
> > > >
> > > > Thank you very much for the review, Mauro. Your comments are very
> > > much
> > > > appreciated.
> > >
> > > How does one use this new support? If I plug in my laptop to my TV,
> > > will using the TV's remote automatically send those key events to
> > > the laptop?
> >
> > It depends on the hardware that is used in your laptop to handle HDMI.
> > If there is hardware support for CEC then this framework can be used
> > to create a driver for the laptop's HDMI hardware. Then the laptop
> > will be able to communicate with the TV over CEC - this includes
> > receiving key events from the TV.
> >
> > Currently there are some CEC devices (and drivers) that enable Linux
> > to use CEC, but there is no generic framework for CEC in the Linux
> > kernel. My goal is to introduce such a framework, such that userspace
> > application could work with different hardware using the same
> > interface.
> >
> > Getting back to your question - using this framework. There should be
> > some initialization done by a user space application:
> > - enabling CEC (if needed by the hardware/driver)
> 
> I have 2 machines that this could work on, a Intel Baytrail tablet, and
> a laptop with Intel Haswell. Is that part going to be covered by your
> library, or will there be a drm API for that?

Enabling CEC is done by the CEC framework. The idea is to have it
independent of other frameworks (such as drm, or v4l2).

> 
> > - configuring the connection (e.g. what kind of device should the
> >   laptop appear as, request the TV to pass remote control keys, etc.)
> 
> That's done through the CEC API as well?

Yes.

> 
> > - the TV will also send other CEC messages to the laptop, hence the
> >   application should listen for such messages and act accordingly
> 
> That's easier to deal with :)
> 
> Something like LIRC can be used in the short-term.
> 
> > How this should be done userspace? Definitely, it would be a good
> idea
> > to use a library. Maybe a deamon that does the steps mentioned above
> > would be a good idea? I am working on a simple library implementation
> > that would wrap the kernel ioctls and provide a more user friendly
> > API.
> 
> Great. Do drop me a mail when you have something that I could test.

Will do.

> Cheers

Best wishes,
-- 
Kamil Debski
Samsung R&D Institute Poland