[linux-dvb] Re: CI implementation question

[Johannes Stezenbach <js@convergence.de>]

Andrew de Quincey wrote:
> 
> Out of interest, if a CI module has two slots, and you're using read()/write() 
> to communicate, how do you know which slot to talk to?
> 
> The ca.h in the linuxtv dvb-kernel implies that there is ONE ca device for 
> each CI module, and you select the slot you want when you send the IOCTLS.... 
> whereas if you're using read/write it would be more natural to create a 
> seperate ca devive for each slot..?

The API isn't clearly defined, but each write() takes / read() delivers:

- 1 byte slot number
- 1 byte transport connection id
- and one complete TPDU

IMHO the ioctl() API is cleaner, but the av7110 driver implemented read()
write() instead, and thus this is used by VDR and the Metzler's libdvbci.

Johannes


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