Re: cxusb: How to add CI support?

[Antti Palosaari <crope@iki.fi>]

Moikka!

On 07/23/2014 10:24 PM, Olli Salonen wrote:
> Hi everyone,
>
> I'm in need of advice when it comes to the implementation of the
> drivers. I recently added support for TechnoTrend CT2-4400 DVB-T2
> tuner into the dvb-usb-cxusb module. Now I have gotten another
> TechnoTrend device CT2-4650 and it seems this is more or less the same
> device as CT2-4400 but with an added CI slot. The CI is realized using
> a CIMaX SP2HF chip.

Here is some brief cip info from manufacturer
http://www.smardtv.com/component/zoo/item/cimax.html

> There seems to be support already for the said CIMaX chip, but only in
> combination with cx23885 (drivers/media/pci/cx23885/
> cimax2.c). This cannot be reused directly in my case. When I look at
> the other dvb-usb devices that have CI slot the support for CI has
> been implemented directly in the code of the USB device (for example,
> pctv452e or az6027).

That is because CI driver usually by USB interface firmware. You could 
see also anysee as one of such example more.


> Of course, an easy way to do it is to reuse a lot of code from the
> existing cimax2 and add it in the cxusb. However, I'm not sure if
> that's an ok approach. As I'm relatively new to linux kernel coding,
> I'd like to ask your recommendation for implementing the CI support
> here before the endeavour. Thanks!

Implement CIMaX driver as a standalone SPI (I am not sure if it is SPI 
or I2C) driver, which implements CI (struct dvb_ca_en50221 callbacks). 
Then load it properly, like si2168/si2157 drivers. It could be hard to 
convert cx23885 without a hardware, but don't worry it - you could left 
it as it is.

regards
Antti

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