linux-kernel - Re: [PATCH RESEND] media: rc: gpio-ir-recv: add support for device tree parsing

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Message-ID: <20130208155707.65a0fbab@redhat.com>
Date:	Fri, 8 Feb 2013 15:57:07 -0200
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Cc:	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	Benoit Thebaudeau <benoit.thebaudeau@...ansee.com>,
	David Hardeman <david@...deman.nu>,
	Trilok Soni <tsoni@...eaurora.org>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH RESEND] media: rc: gpio-ir-recv: add support for device
 tree parsing

Em Wed, 06 Feb 2013 18:18:22 +0100
Sebastian Hesselbarth <sebastian.hesselbarth@...il.com> escreveu:

> On 02/06/2013 02:48 PM, Sylwester Nawrocki wrote:
> > On 02/06/2013 09:03 AM, Sebastian Hesselbarth wrote:
> >> This patch adds device tree parsing for gpio_ir_recv platform_data and
> >> the mandatory binding documentation. It basically follows what we already
> >> have for e.g. gpio_keys. All required device tree properties are OS
> >> independent but optional properties allow linux specific support for rc
> >> protocols and maps.
> >>
> >> There was a similar patch sent by Matus Ujhelyi but that discussion
> >> died after the first reviews.
> >>
> >> Signed-off-by: Sebastian Hesselbarth<sebastian.hesselbarth@...il.com>
> >> ---
> > ...
> >> diff --git a/Documentation/devicetree/bindings/media/gpio-ir-receiver.txt b/Documentation/devicetree/bindings/media/gpio-ir-receiver.txt
> >> new file mode 100644
> >> index 0000000..937760c
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/media/gpio-ir-receiver.txt
> >> @@ -0,0 +1,20 @@
> >> +Device-Tree bindings for GPIO IR receiver
> >> +
> >> +Required properties:
> >> +	- compatible = "gpio-ir-receiver";
> >> +	- gpios: OF device-tree gpio specification.
> >> +
> >> +Optional properties:
> >> +	- linux,allowed-rc-protocols: Linux specific u64 bitmask of allowed
> >> +	    rc protocols.
> >
> > You likely need to specify in these bindings documentation which bit
> > corresponds to which RC protocol.
> >
> > I'm not very familiar with the RC internals, but why it has to be
> > specified statically in the device tree, when decoding seems to be
> > mostly software defined ? I might be missing something though..
> 
> Sylwester,
> 
> I am not familiar with RC internals either. Maybe somebody with more
> insight in media/rc can clarify the specific needs for the rc subsystem.
> I was just transferring the DT support approach taken by gpio_keys to
> gpio_ir_recv as I will be using it on mach-dove/cubox soon.

The allowed rc protocol field are there for devices with hardware IR
support, where only a limited set of remote protocols can be decoded.

For software decoders RC_BIT_ALL is the proper setup. Users of course
can change it via sysfs at runtime, or a software decoder may be
disabled at compilation time by not selecting its CONFIG_* var.

> > Couldn't this be configured at run time, with all protocols allowed
> > as the default ?
> 
> Actually, this is how the internal rc code works. If there is nothing
> defined for allowed_protocols it assumes that all protocols are supported.
> That is why above node properties are optional.
> 
> About the binding documentation of allowed_protocols, rc_map, or the
> default behavior of current linux code, I don't think they will stay
> in-sync for long. 

Why not? The rc_map name is used either by Kernelspace or by Userspace,
in order to provide the IR keycode name that matches a given keytable.

There's no plans to change it, even in the long term.

Regards,
Mauro.

-- 

Cheers,
Mauro
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