Re: [PATCH] [media] nec decoder: wrong bit order for nec32 protocol

[Sean Young <sean@mess.org>]

On Tue, Nov 22, 2016 at 09:19:19AM -0500, Jarod Wilson wrote:
> On Tue, Nov 22, 2016 at 11:35:06AM -0200, Mauro Carvalho Chehab wrote:
> > Em Wed,  9 Nov 2016 16:13:35 +0000
> > Sean Young <sean@mess.org> escreveu:
> > 
> > > The bits are sent in lsb first. Hardware decoders also send nec32
> > > in this order (e.g. dib0700). This should be consistent, however
> > > I have no way of knowing which order the LME2510 and Tivo keymaps
> > > are (the only two kernel keymaps with NEC32).
> > 
> > Hmm.. the lme2510 receives the scancode directly. So, this
> > patch shouldn't affect it. So, we're stuck with the Tivo IR.
> > 
> > On Tivo, only a few keys (with duplicated scancodes) don't start with
> > 0xa10c. So, it *seems* that this is an address.

The problem here is that each *byte* is sent lsb first, so only the 
ordering within each byte would change. 

> > The best here would be to try to get a Tivo remote controller[1], and
> > do some tests with a driver that has a hardware decoder capable of
> > output NEC32 data, and some driver that receives raw IR data in
> > order to be sure.
> > 
> > In any case, we need to patch both the NEC32 decoder and the table
> > at the same time, to be 100% sure.
> > 
> > [1] or some universal remote controller that could emulate
> > the Tivo's scan codes. I suspect that the IR in question is
> > this one, but maybe Jarod could shed some light here:
> > 	https://www.amazon.com/TiVo-Remote-Control-Universal-Replacement/dp/B00DYYKA04
> 
> Been away from the game for a few years now, so there are a good number of
> cobwebs in this section of my brain... I'm pretty sure I do have both a
> remote and receiver on hand that would fit the bill here though. Is the
> question primarily about what actually gets emitted by the TiVo remote?

Yes, it is. Hardware nec decoders send each byte lsb first, but 
ir-nec-decoder.c decoder does msb first for nec32 (not for extended nec or
plain nec).

If we have a mode2 recording of the remote (and if we know what button it
is), then we can replay it against a hardware nec decoder and the software
decoder. Rather than mode2, this can also be done with ir-ctl which is in
v4l-utils git.

Alternatively simply checking if the tivo keymap works with the
software decoder (mceusb hardware for example) should be sufficient.

That would be really helpful, thanks.


Sean