[linux-dvb] Re: Supporting the remote control of the Nebula DVB-Tcard.

[Holger Waechtler <holger@convergence.de>]

Mikael Rosbacke wrote:
> Greetings fellow DVB citizens.
>
> I have a Nebula DVB-T card and it comes bundled with a universal remote 
> control. As far as I can tell, it does not have support in lirc.
> I've spent some time tracing the the circuit and it requres collaboration from 
> both the bt878 and the interrupt-handlers to make sense of the signal. The 
> short story is that the flank (either positive or negative) from the 
> IR-sensor triggers an interrupt through a D-latch, which has to be reset by 
> the bt878 before the next interrupt arrives. It is then up to the driver to 
> meassure the timing between interrupts to dechiper the actual control word.
> This is my current understanding of the circuit but I havn't really looked 
> into the role of bt878 yet, which might change my perception.
>
> I'd figured a driver for this remote sensor would be a good starting project 
> to try some kernel module programming, so I'd like some feedback on the idea 
> of API to this module.
>
> I plan to create a new special file, say ir0 alongside the others in the 
> adapter directory. This could e.g. be /dev/dvb/adapter0/ir0.
> This special file support read operations, where each read returns the latest 
> control word not yet read. The control words are stored in a fifo and there 
> should be a ioctl call for removing all the old data, i.e. clearing the FIFO 
> queue.
>
> Is this a recommended approach? Are there any issues I should consider before 
> I dive to deeply into this little project?
Existing IR controller drivers use the linux input event device layer. 
Take a look into the example drivers: 
dvb-kernel/linux/drivers/media/dvb/ttpci/av7110_ir.c and
dvb-kernel/linux/drivers/media/dvb/ttpci/budget-ci.c.

A few days ago there was a short discussion on this list intiated by 
Adrian Look who proposed to generalize the IR control code, maybe you 
want to start here: 
http://www.linuxtv.org/mailinglists/linux-dvb/2003/11-2003/msg00473.html

hope this helps to dig deeper,

Holger



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