[libcamera-devel] [PATCH 0/3] Add SensorTemperature control

[Dave Stevenson]

Hi Naush and Jean-Michel

On Thu, 23 Jun 2022 at 15:56, Naushir Patuck via libcamera-devel
<libcamera-devel at lists.libcamera.org> wrote:
>
> Hi Jean-Michel,
>
> On Thu, 23 Jun 2022 at 15:51, Jean-Michel Hautbois <jeanmichel.hautbois at yoseli.org> wrote:
>>
>>
>>
>> On 23/06/2022 16:50, Jean-Michel Hautbois via libcamera-devel wrote:
>> > Hi Naushir,
>> >
>> > Thanks for the series !
>> >
>> > On 23/06/2022 16:44, Naushir Patuck via libcamera-devel wrote:
>> >> Hi,
>> >>
>> >> This series adds a sensor temperature metadata control to libcamera.
>> >> This
>> >> control is returned out through Request metadata when available.
>> >> There is an
>> >> open PR [1] to enable the temperature sensor on the imx477 on the
>> >> Raspberry Pi
>> >> platforms.
>> >>
>> >> At present, there is no mechanism in V4L2 to return the temperature
>> >> from the
>> >> sensor device driver, so we rely on the embedded data to fetch the
>> >> values every
>> >> frame.
>> >
>> > I think this PR along with a V4L2 control introduction
>> > (V4L2_CID_TEMPERATURE :-) ?) could be interesting to be sent to the
>> > linux-media ML at the same time ?
>
>
> I was hoping to decouple this with V4L2 changes for now.  From what I can tell,
> the topic of V4L2_CID_TEMPERATURE is a long ongoing discussion, and my
> change here does not rely on it.  So our users can get this feature earlier!

I've flagged it for discussion at the proposed Media Summit alongside
ELCE in September -
https://www.spinics.net/lists/linux-media/msg212772.html

Laurent has responded in support of V4L2_CID_TEMPERATURE in preference
to hwmon API, but that still doesn't make it a done deal.
When Benjamin brought it up in
https://lore.kernel.org/linux-media/20220415111845.27130-3-benjamin.mugnier@foss.st.com/,
it became quite a long debate with no resolution, leading to the patch
just being dropped.

As Naush says, with imx477 (and others) carrying this value in
embedded metadata, we may as well extract it from there and avoid the
complication. It'll actually be a more up to date value than reading
it on demand over I2C.

  Dave

>>
>>
>> I forgot to ask the use case though ? :-)
>
>
> We have had a few requests for this feature, see https://github.com/raspberrypi/libcamera-apps/issues/306
> for the most recent one where the temperature value is useful for long exposures to
> help with dark frame subtraction in post processing for astrophotography.
>
> Regards,
> Naush
>
>>
>>
>> >
>> > JM
>> >
>> >>
>> >> Thanks,
>> >> Naush
>> >>
>> >> [1] https://github.com/raspberrypi/linux/pull/5067
>> >>
>> >> Naushir Patuck (3):
>> >>    libcamera: controls: Add SensorTemperature control
>> >>    ipa: raspberrypi: Add sensor temperature to DeviceStatus
>> >>    ipa: raspberrypi: imx477: Get sensor temperature from embedded data
>> >>
>> >>   src/ipa/raspberrypi/cam_helper.cpp               |  7 ++++---
>> >>   src/ipa/raspberrypi/cam_helper_imx477.cpp        |  5 ++++-
>> >>   src/ipa/raspberrypi/controller/device_status.cpp |  3 +++
>> >>   src/ipa/raspberrypi/controller/device_status.h   |  4 +++-
>> >>   src/ipa/raspberrypi/raspberrypi.cpp              |  2 ++
>> >>   src/libcamera/control_ids.yaml                   | 10 ++++++++++
>> >>   6 files changed, 26 insertions(+), 5 deletions(-)
>> >>