Re: [PATCHv2] adp1653: make ->power() method optional

[Sakari Ailus <sakari.ailus@iki.fi>]

On Thu, Aug 18, 2011 at 02:32:02PM +0300, Andy Shevchenko wrote:
> On Thu, 2011-08-18 at 14:22 +0300, Andy Shevchenko wrote: 
> > The ->power() could be absent or not used on some platforms. This patch makes
> > its presence optional.
> > 
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > Cc: Sakari Ailus <sakari.ailus@iki.fi>
> > ---
> >  drivers/media/video/adp1653.c |    5 +++++
> >  1 files changed, 5 insertions(+), 0 deletions(-)
> > 
> > diff --git a/drivers/media/video/adp1653.c b/drivers/media/video/adp1653.c
> > index 0fd9579..f830313 100644
> > --- a/drivers/media/video/adp1653.c
> > +++ b/drivers/media/video/adp1653.c
> > @@ -329,6 +329,11 @@ adp1653_set_power(struct v4l2_subdev *subdev, int on)
> >  	struct adp1653_flash *flash = to_adp1653_flash(subdev);
> >  	int ret = 0;
> >  
> > +	/* There is no need to switch power in case of absence ->power()
> > +	 * method. */
> > +	if (flash->platform_data->power == NULL)
> > +		return 0;
> > +
> >  	mutex_lock(&flash->power_lock);
> >  
> >  	/* If the power count is modified from 0 to != 0 or from != 0 to 0,
> 
> He-h, I guess you are not going to apply this one.
> The patch breaks init logic of the device. If we have no ->power(), we
> still need to bring the device to the known state. I have no good idea
> how to do this.

I don't think it breaks anything actually. Albeit in practice one is still
likely to put the adp1653 reset line to the board since that lowers its power
consumption significantly.

Instead of being in power-up state after opening the flash subdev, it will
reach this state already when the system is powered up. At subdev open all
the relevant registers are written to anyway, so I don't see an issue here.

I think either this one, or one should check in probe() that the power()
callback is non-NULL.

The board code is going away in the near future so this callback will
disappear eventually anyway. The gpio code in the board file should likely
be moved to the driver itself. That assumes that there will be a gpio which
can be used to enable and disable the device and I'm not fully certain this
is generic enough. Hopefully it is, but I don't know where else the adp1653
would be used than on the N900.

Cheers,

-- 
Sakari Ailus
sakari.ailus@iki.fi