Re: [PATCH v3] media: imx319: Add imx319 camera sensor driver

[jacopo mondi <jacopo@jmondi.org>]

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Hi Tomasz,

On Fri, May 25, 2018 at 03:18:38PM +0900, Tomasz Figa wrote:
> On Fri, May 25, 2018 at 5:47 AM Sakari Ailus <sakari.ailus@linux.intel.com>
> wrote:
>
> > Hi Jacopo,
>
> > On Thu, May 24, 2018 at 10:07:38PM +0200, jacopo mondi wrote:
> > ...
> > > > > about that, but I wonder why setting controls should be enabled only
> > > > > when streaming. I would have expected runtime_pm_get/put in
> subdevices
> > > > > node open/close functions not only when streaming. Am I missing
> something?
> > > >
> > > > You can do it either way. If powering on the sensor takes a long
> time, then
> > > > doing that in the open callback may be helpful as the user space has
> a way
> > > > to keep the device powered.
> > >
> > > Ok, so I assume my comment could be ignored, assuming is fine not
> > > being able to set control if the sensor is not streaming. Is it?
>
> > I'd say so. From the user's point of view, the sensor doesn't really do
> > anything when it's in software standby mode.
>
> Just to make sure we're on the same page, the code actually does nothing
> when the sensor is not in streaming mode (i.e. powered off). When stream is
> being started, the V4L2 control framework will call s_ctrl for all the
> controls in the handler to synchronize hardware state and this is when all
> the controls set before powering on will actually be programmed into the
> hardware registers.

Thanks, I had missed that part.

I quickly tried searching for 's_ctrl' calls in the v4l2-core/ code
and I've found nothing that invokes that in response to a streaming
start operation. Just if you happen to have any reference handy, could
you please point me to that part, just for my better understanding?

Thanks
   j

>
> Best regards,
> Tomasz

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