Re: [PATCH v2 2/5] media: v4l: ctrls: Add a control for temperature

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Wed, Apr 20, 2022 at 09:19:53AM -0700, Guenter Roeck wrote:
> On 4/20/22 08:19, Benjamin Mugnier wrote:
> [ ... ]
> >>
> >> It's the two most common use cases for imaging sensor temperature
> >> measurements that I know of. My question to Benjamin is if he has the
> >> same and/or other use cases.
> >>
> > 
> > Just like you said in a previous mail. This temperature sensor can
> > be used to implement a retroactive loop from the host according to
> > its value, such as noise correction for instance.
> > We don't have anything in the Linux user space that implements this
> > yet, this was in anticipation.
> > So dropping it is fine, I will come back to it if need be ;)
> 
> When you implement this in userspace, you might want to consider situations
> where the temperature is _not_ reported via media controls (which might
> at least in theory happen if the temperature sensor is not part of the
> v4l device), or for existing drivers with hwmon support
> (drivers/media/i2c/video-i2c.c comes into mind).

That's a good point. I wouldn't expect external temperature sensors to
be very useful for this use case though, as what we really need is the
temperature of the camera sensor die.

-- 
Regards,

Laurent Pinchart