[linux-dvb] Re: Getting IR-codes directly from DVB-S?

[Oliver Endriss <o.endriss@gmx.de>]

On Monday 13 October 2003 12:07, Vojtech Pavlik wrote:
> On Mon, Oct 13, 2003 at 05:41:12AM +0200, Oliver Endriss wrote:
> 
> > Basically we need 2 pass-through ioctls:
> > - set low level configuration
> > - get low level configuration
> 
> I'm not really keen on passing ioctl()s to drivers, but if there is no
> other way around, then well ...

Well, we need a clean interface to pass some remote-specific parameters
to the low-level driver. Until now this is done using /proc/av7110_ir.
But this is just a hack. ;-)

> > Each of these ioctls could have several sub-types:
> > - access config flags (for example: signal inversion)
> > - access keymap (raw addr/code <-> key code mapping)
> > - ...
> > 
> > It should be possible to read the current keymap from the device.
> > This way one could write something like a keymap editor, or
> > add another remote control to a loaded keymap.
> 
> Well, it is currently possible to read a keymap from a keyboard via the
> event interface. It doesn't efficiently handle sparse keycode tables,
> though, like the remote seems to be using (address + code).

Ok, this is a new feature in kernel 2.6. (I checked 2.4 sources only.)
Typically, a remote control has less that 50 keys, so it would have
been better to read/write keycodes using a low-level driver function
and move the implementation (array or list) into the driver.

For a reasonable implementation, we need 13-bits or more for scancodes
(5 bits address + 8 bits data). We have to select keycode size 16 bits.
So we need 8K x 2 = 16Kbyte for the keymap, while 100 bytes would have
been sufficient. No problem right now, but what if we need 16/24/32 bit
scancodes?

> > Another feature which is really missing in the event device stuff is a
> > interface to read *raw* keycodes from the device.
> 
> Indeed. That's because the abstraction is placed in the level of defined
> keycodes. Since the raw codes are device specific, they should be
> contained in the drivers as much as possible. However, I do see that
> keymap editors will need the access to these.
>
> At the moment it's possible to load some kind of 1:1 mapping keytable
> and then look at the keycodes, and then look at what keycodes are
> coming. This again doesn't handle sparse tables very well (number of
> scancodes >> number of keycodes).

Unfortunately, keycodes are currently limited to 9 bits (KEY_MAX).
Therefore this approach does not work. :-(
Currently I'm using some tricks to work around the problem, but that's
causing trouble again...

> I'm considering to add a new 'raw' event type for this.

This would be great!

Oliver


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