cxusb: How to add CI support?

cxusb: How to add CI support?

[Olli Salonen]

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.

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).

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!

Cheers,
-olli

Re: cxusb: How to add CI support?

[Antti Palosaari]

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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