Re: em28xx: msi Digivox ATSC board id [0db0:8810]

[Mauro Carvalho Chehab <mchehab@redhat.com>]

Em Thu, 13 Dec 2012 18:07:16 -0200
Mauro Carvalho Chehab <mchehab@redhat.com> escreveu:

> Em Tue, 11 Dec 2012 21:51:34 +0100
> Frank Schäfer <fschaefer.oss@googlemail.com> escreveu:
> 
> > Am 10.12.2012 21:48, schrieb Antti Palosaari:
> > > On 12/10/2012 09:24 PM, Frank Schäfer wrote:
> > >> Am 10.12.2012 18:57, schrieb Antti Palosaari:
> > >>> On 12/10/2012 06:13 PM, Devin Heitmueller wrote:
> > >>>> On Mon, Dec 10, 2012 at 11:01 AM, Frank Schäfer
> > >>>>> Adding a new property to the RC profile certainly seems to be the
> > >>>>> cleanest solution.
> > >>>>> Do all protocols have paritiy checking ? Otherwise we could add a new
> > >>>>> type RC_TYPE_NEC_NO_PARITY.
> > >>>>> OTOH, introducing a new bitfield in struct rc_map might be usefull
> > >>>>> for
> > >>>>> other flags, too, in the future...
> > >>>>
> > >>>> It's probably also worth mentioning that in that mode the device
> > >>>> reports four bytes, not two.  I guess perhaps if parity is ignored it
> > >>>> reports the data in some other format?  You will probably have to do
> > >>>> some experimentation there.
> > 
> > ...
> > 
> > >>>
> > >>> Uh, current em28xx NEC implementation is locked to traditional 16 bit
> > >>> NEC, where is hw checksum used.
> > >>>
> > >>> Implementation should be changed to more general to support 24 and 32
> > >>> bit NEC too. There is multiple drivers doing already that, for example
> > >>> AF9015.
> > >>>
> > >>
> > >> Hmm... are there and documents (, links, books, ...) where I can learn
> > >> more about all those RC protocols ?
> > >
> > > Specification comes here:
> > > NEC send always 32 bit, 4 bytes. There is 3 different "sub" protocols:
> > >
> > > 1) 16bit NEC standard, 1 byte address code, 1 byte key code
> > > full 4 byte code: AA BB CC DD
> > > where:
> > > AA = address code
> > > BB = ~address code
> > > CC = key code
> > > DD = ~key code
> > >
> > > checksum:
> > > AA + BB = 0xff
> > > CC + DD = 0xff
> > >
> > > 2) 24bit NEC extended, 2 byte address code, 1 byte key code
> > > full 4 byte code: AA BB CC DD
> > > where:
> > > AA = address code (MSB)
> > > BB = address code (LSB)
> > > CC = key code
> > > DD = ~key code
> 
> Actually, on both above, AFAIKT, instead of "key code", the last 8
> bits are called as "command code" at the specs.
> > >
> > > 3) 32bit NEC full, 4 byte key code
> > > full 4 byte code: AA BB CC DD
> > > where:
> > > AA =
> > > BB =
> > > CC =
> > > DD =
> > >
> > > I am not sure if there is separate parts for address and key code in
> > > case of 32bit NEC. See some existing remote keytables if there is any
> > > such table. It is very rare protocol. 1) and 2) are much more common.
> 
> On all 32-bits NEC IR's I tested, this is mapped as:
> 
> address code = AABBCC
> command code = DD

Hmm... actually, tivo NEC IR seems to be, instead:

address code = AABB
command code = CCDD

       	{ 0xa10c900f, KEY_MEDIA },      /* TiVo Button */
        { 0xa10c0807, KEY_POWER2 },     /* TV Power */
       	{ 0xa10c8807, KEY_TV },         /* Live TV/Swap */
        { 0xa10c2c03, KEY_VIDEO_NEXT }, /* TV Input */
        { 0xa10cc807, KEY_INFO },
        { 0xa10cfa05, KEY_CYCLEWINDOWS }, /* Window */
        { 0x0085305f, KEY_CYCLEWINDOWS },
        { 0xa10c6c03, KEY_EPG },        /* Guide */

(I guess that the second KEY_CYCLEWINDOWS is likely due to some different
IR device - the same 0x0085 pattern with duplicated keycode also happens
on key '8' on this table).

It should be noticed that those 24/32 bit "extended-NEC" aren't part of the
NEC protocol specs, AFAIKT. It is just some manufacturer's decision to use
a NEC chip to produce non-parity scancodes.

The manufacturer can obviously do whatever it wants with the protocol 
keycode, either using some standard, or to inventing their own way.
That's one of the reasons why we don't split the code into address/command
inside the RC core. Tthe other one is that a table lookup is simpler than
if this were broken into two separate fields.

Regards,
Mauro