Re: Question about saa7115

[Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxx>]

On Wed, 6 Feb 2008 17:44:05 -0800
"Guillaume Quintard" <guillaume.quintard@xxxxxxxxx> wrote:

> Hi,
> (I'm not sure it's the right place, but I couldn't find any better
> place, so, if there is, please let me know)

This is the proper place ;)

> I'm kinda new to V4L2 (and kernel drivers in general) and I've been
> asked to se if I could control a saa7115 on an embedded linux
> platform, using the V4L2 driver.
> the driver loads without a problem, it creates an interface in /dev/,
> but that a I2C (89) file, and not a video (81) one. The thing is I
> have two saa7115 on the I2C bus, and I don't how to issue my command
> to the one I want.
> 
> Well, from what I understood, I can send instructions to the bus using
> ioctl() and /dev/i2c-0, but these are i2c/smbus commands, not V4L2
> ones, right ?
> 
> I read the sources and I still don't have a clue what I'm supposed to
> do, could you please give me a few hints ?

On most devices, you don't have direct access to i2c bus, since it is located
on a separate board. So, v4l drivers creates a host driver with PCI or USB bus.
The host driver then implements i2c methods. This is the case of cx88-i2c, for
example.

On embedded processors, you generally attach devices directly to the CPU i2c
bus. In this case, you'll need to implement a host v4l2 module for your
processor, and use it to access the i2c device.

Cheers,
Mauro

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