2009/7/12 Hans Verkuil <hverkuil@xxxxxxxxx>:
> On Saturday 11 July 2009 13:02:33 Dongsoo, Nathaniel Kim wrote:
>> Hi,
>>
>> The thing is - Is it possible to make the subdev device not to be
>> turned on in registering process using any of v4l2_i2c_new_subdev*** ?
>> You can say that I can ignore the i2c errors in booting process, but I
>> think it is not a pretty way.
>>
>> And for the reason I'm asking you about this, I need you to consider
>> following conditions I carry.
>>
>> 1. ARM embedded platform especially mobile handset.
>> 2. Mass production which is very concerned about power consumption.
>> 3. Strict and automated test process in product line.
>>
>> So, what I want to ask you is about s_config subdev call which is
>> called from every single I2C subdev load in some kind of probe
>> procedure. As s_config is supposed to do, it tries to initialize
>> subdev device. which means it needs to turn on the subdev to make that
>> initialized.
>
> Actually, all s_config does is to pass the irq and platform_data arguments
> to the subdev driver. The subdev driver can just store that information
> somewhere and only use it when needed. It does not necessarily have to turn
> on the sub-device.
>
> Whether to just store this info or turn on the sub-device is something that
> each subdev driver writer has to decide.
>
> Note that this really has nothing to do with the existance of s_config:
> s_config was only introduced in order to support legacy v4l2 drivers and
> subdev drivers. In the (far?) future this will probably disappear and this
> information will always be passed via struct i2c_board_info.
>
>> But as I mentioned above if we make the product go through the product
>> line, it turns on the subdev device even though nobody intended to
>> turn the subdev on. It might be an issue in product vendor's point of
>> view, because there should be a crystal clear reason for the
>> consumption of power the subdev made. I'm working on camera device and
>> speaking of which, camera devices are really power consuming device
>> and some camera devices even take ages to be initialized as well.
>>
>> So far I hope I made a good explanation about why I'm asking you about
>> following question.
>> By the way, it seems to be similar to the issue I've faced whe using
>> old i2c driver model..I mean probing i2c devices on boot up sequence.
>
> That at least should no longer be a problem anymore (as long as you don't
> use the address-probing variants).
>
> Regards,
>
> Hans
>
> --
> Hans Verkuil - video4linux developer - sponsored by TANDBERG
>
Hello Hans,
I just needed an API for initializing soc camera device ;-( but after
reading your mail, it seems to be that I'm using a wrong API.
As you know, almost every cmos camera module needs to be programmed
through I2C(or SPI) when it is turned on to be initialized. And I
thought that s_config is the one which could be used.
If I'm getting wrong, which one can I use for that initialization
purpose? I referenced every v4l2 device driver in linuxtv repository
and cherry-picked the API in my own way.
Cheers,
Nate
--
=
DongSoo, Nathaniel Kim
Engineer
Mobile S/W Platform Lab.
Digital Media & Communications R&D Centre
Samsung Electronics CO., LTD.
e-mail : dongsoo.kim@xxxxxxxxx
dongsoo45.kim@xxxxxxxxxxx
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