Re: [PATCH 1/6 v4] media: V4L2: support asynchronous subdevice registration

[Sylwester Nawrocki <sylvester.nawrocki@gmail.com>]

Hi,

On 01/08/2013 11:35 AM, Laurent Pinchart wrote:
>>>>> If we need a workaround, I'd rather pass the device name in addition
>>>>> to the I2C adapter number and address, instead of embedding the
>>>>> workaround in this new API.
>>>>
>>>> ...or we can change the I2C subdevice name format. The actual need to do
>>>>
>>>> 	snprintf(clk_name, sizeof(clk_name), "%s %d-%04x",
>>>> 	
>>>> 		 asdl->dev->driver->name,
>>>> 		 i2c_adapter_id(client->adapter), client->addr);
>>>>
>>>> in soc-camera now to exactly match the subdevice name, as created by
>>>> v4l2_i2c_subdev_init(), doesn't make me specifically happy either. What
>>>> if the latter changes at some point? Or what if one driver wishes to
>>>> create several subdevices for one I2C device?
>>>
>>> The common clock framework uses %d-%04x, maybe we could use that as well
>>> for clock names ?
>>
>> And preserve the subdevice names? Then matching would be more difficult
>> and less precise. Or change subdevice names too? I think, we can do the
>> latter, since anyway at any time only one driver can be attached to an I2C
>> device.
>
> That's right. Where else is the subdev name used ?

Subdev names are exposed to user space by the media controller API.
So they are really part of an ABI, aren't they ?

Also having I2C bus number or I2C slave address as part of the subdev
name makes it more difficult to write portable applications. Hence
in sensor drivers I used to overwrite subdev name to remove I2C bus
and slave address, as the format used v4l2_i2c_subdev_init() seemed
highly unsuitable..

--

Regards,
Sylwester