On Wednesday, December 08, 2010 05:12:22 Kim, HeungJun wrote:
> Hi Hans and everyone,
>
> I wonder if the subdev driver need pm features, like a power-off when suspend
> and power-on when resume.
> Commonly, It seems alright that the platform driver using this subdev driver
> must do such process.
> But, thinking deeply, irrelevantly at this dependency of the platform and the
> subdev,
> I think the subdev driver must support pm features.
> If the platform driver dosen't support subdev driver's pm, the ISP or camera
> device controlled with non-pm-support subdev driver, may have a problems when
> the system is suspended/resumed.
>
> In the subev driver, using pm or not. which one is right??
Both. It depends on the type of hardware. Most subdevs are i2c drivers. And
pm is a standard feature of such drivers. Proper pm is unfortunately rarely
implemented in v4l drivers, but there are a few i2c subdev drivers that do it.
If a subdev is not part of a i2c/spi bus, then pm is more likely handled by the
main v4l driver which will call s_power whenever a subdev needs to power up or
down.
Regards,
Hans
--
Hans Verkuil - video4linux developer - sponsored by Cisco
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