[linux-dvb] Supporting the remote control of the Nebula DVB-T card.

[Mikael Rosbacke <rosbacke@nada.kth.se>]

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?

--- Mikael R




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