linux-kernel - Re: [RFC] What are the goals for the architecture of an in-kernel IR system?

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Message-ID: <4BB2E554.6030308@redhat.com>
Date:	Wed, 31 Mar 2010 03:01:56 -0300
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jon Smirl <jonsmirl@...il.com>, Pavel Machek <pavel@....cz>,
	Krzysztof Halasa <khc@...waw.pl>,
	hermann pitton <hermann-pitton@...or.de>,
	Christoph Bartelmus <lirc@...telmus.de>, awalls@...ix.net,
	j@...nau.net, jarod@...hat.com, jarod@...sonet.com,
	kraxel@...hat.com, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	superm1@...ntu.com
Subject: Re: [RFC] What are the goals for the architecture of an in-kernel
 IR system?

David Härdeman wrote:
> On Sun, Mar 28, 2010 at 09:51:17PM -0300, Mauro Carvalho Chehab wrote:
>> I spoke too soon... removing the index causes a problem at the read ioctl: there's no way
>> to retrieve just the non-sparsed values.
>>
>> There's one solution that would allow both read/write and compat to work nicely,
>> but the API would become somewhat asymmetrical:
>>
>> At get (EVIOCGKEYCODEBIG):
>> 	use index/len as input and keycode/scancode as output;
>>
>> At set (EVIOCSKEYCODEBIG):
>> 	use scancode/keycode/len as input (and, optionally, index as output).
>>
> 
> This was exactly the approach I had in mind when I suggested using 
> indexes.

Doesn't work perfectly. The asymmetry has a side effect on the internal logic: 

EVIOCGKEYCODEBIG should be implemented with a pseudo-code like:
	kt_entry = getkeycodebig_from_index(index);

EVIOCSKEYCODEBIG should be implemented with a pseudo-code like:
	kt_entry = getkeycodebig_from_scan(scan, len);
	old_key = kt_entry->keycode;

	kt_entry->keycode = newkey;
	if (setkeycodebig(kt_entry) == 0)
		keyup(old_key);

As you see, the input parameters for the getkeycodebig*() are different.

So, this approach requires 3 ops instead of 2. Yet, as scancode->keycode is
needed anyway, this doesn't actually hurts.

I just added the patches that implement those two ioctls on my IR development tree.
I tested only the original EVIOCGKEYCODE/EVIOSGKEYCODE and calling a clear_table
function using EVIOCSKEYCODEBIG via emulation.

My next step is to test the remaining ir-keytable functions via emulation, and then
implement the *BIG ioctls at ir-core, for testing.

I haven't test yet the *keycode*default methods. 

After having it fully tested, I'll submit the complete input ioctl patch via ML.

-- 

Cheers,
Mauro
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