From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mauro Carvalho Chehab <mchehab@redhat.com>
Subject: Re: [RFC] What are the goals for the architecture of an in-kernel
 IR  system?
Date: Mon, 07 Dec 2009 22:00:20 -0200
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To: Krzysztof Halasa <khc@pm.waw.pl>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>, Gerd Hoffmann <kraxel@redhat.com>, Jarod Wilson <jarod@wilsonet.com>, Christoph Bartelmus <lirc@bartelmus.de>, awalls@radix.net, j@jannau.net, jarod@redhat.com, jonsmirl@gmail.com, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, superm1@ubuntu.com

Krzysztof Halasa wrote:
> Mauro Carvalho Chehab <mchehab@redhat.com> writes:
> 

>> struct input_keytable_entry {
>>  	u16	index;
>>  	u64	scancode;
>>  	u32	keycode;
>> } __attribute__ ((packed));
>>
>> (the attribute packed avoids needing a compat for 64 bits)
> 
> Maybe { u64 scancode; u32 keycode; u16 index; u16 reserved } would be a
> bit better, no alignment problems and we could eventually change
> "reserved" into something useful.
> 
> But I think, if we are going to redesign it, we better use scancodes of
> arbitrary length (e.g. protocol-dependent length). It should be opaque
> except for the protocol handler.

Yes, an opaque type for scancode at the userspace API can be better, but
passing a pointer to kernel will require some compat32 logic (as pointer
size is different on 32 and 64 bits).

We may use something like an u8[] with an arbitrary large number of bytes.
In this case, we need to take some care to avoid LSB/MSB troubles.

Cheers,
Mauro.