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

[Naushir Patuck]

On Thu, 23 Jun 2022 at 16:12, Dave Stevenson <dave.stevenson at raspberrypi.com>
wrote:

> 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.
>

That's a good point - embedded data values will always be guaranteed to be
synced with the
frame in question.  But sync granularity might not be such a big deal for a
temperature measurement...

Naush



>
>   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(-)
> >> >>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.libcamera.org/pipermail/libcamera-devel/attachments/20220623/bed694a7/attachment.htm>