[v2,0/2] CameraSensorHelper measurement tool and guide
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Message ID 20260810174611.2472046-1-john.cronin@opcenter.com
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John Cronin Aug. 10, 2026, 5:46 p.m. UTC 
Hi,

Thanks Laurent for the review of the v1 series, and for looping in
Barnabas and Stefan.

Changes since v1:

- Do not install the measurement script (developer tool only; run from
  the libcamera source tree). Dropped the utils/meson.build install_data
  rule and the libcamera-measure-analogue-gain rename.
- Documentation notes that the helper is not packaged and should be run
  as ./utils/measure-analogue-gain.py from a checkout.

On longer-term direction:

- camshark: happy to leave that for later if Stefan sees a fit for a
  plugin; this series keeps a small standalone utils script for now, as
  you suggested is fine for a first merge.
- Setting analogue gain through libcamera rather than v4l2-ctl: agreed
  that is nicer. Happy to revisit once Barnabas AGC rework exposes raw
  AnalogueGain for sensors without a helper (or with one). The current
  tool documents the v4l2-ctl path that works today for soft-ISP helper
  bring-up.

Patches below (v2).

Thanks,
John Cronin


John Cronin (2):
  utils: Add measure-analogue-gain helper
  Documentation: Add Camera Sensor Helper guide

 Documentation/guides/camera-sensor-helper.rst | 148 ++++++
 Documentation/index.rst                       |   1 +
 Documentation/meson.build                     |   1 +
 utils/measure-analogue-gain.py                | 466 ++++++++++++++++++
 4 files changed, 616 insertions(+)
 create mode 100644 Documentation/guides/camera-sensor-helper.rst
 create mode 100755 utils/measure-analogue-gain.py

Comments

Barnabás Pőcze Aug. 11, 2026, 12:08 p.m. UTC | #1 
Hi

2026. 08. 10. 19:46 keltezéssel, John Cronin írta:
> Hi,
> 
> Thanks Laurent for the review of the v1 series, and for looping in
> Barnabas and Stefan.
> 
> Changes since v1:
> 
> - Do not install the measurement script (developer tool only; run from
>    the libcamera source tree). Dropped the utils/meson.build install_data
>    rule and the libcamera-measure-analogue-gain rename.
> - Documentation notes that the helper is not packaged and should be run
>    as ./utils/measure-analogue-gain.py from a checkout.
> 
> On longer-term direction:
> 
> - camshark: happy to leave that for later if Stefan sees a fit for a
>    plugin; this series keeps a small standalone utils script for now, as
>    you suggested is fine for a first merge.
> - Setting analogue gain through libcamera rather than v4l2-ctl: agreed
>    that is nicer. Happy to revisit once Barnabas AGC rework exposes raw
>    AnalogueGain for sensors without a helper (or with one). The current
>    tool documents the v4l2-ctl path that works today for soft-ISP helper
>    bring-up.

I suppose in that case you could just create a capture script for `cam` and run that?


> 
> Patches below (v2).
> 
> Thanks,
> John Cronin
> 
> 
> John Cronin (2):
>    utils: Add measure-analogue-gain helper
>    Documentation: Add Camera Sensor Helper guide
> 
>   Documentation/guides/camera-sensor-helper.rst | 148 ++++++
>   Documentation/index.rst                       |   1 +
>   Documentation/meson.build                     |   1 +
>   utils/measure-analogue-gain.py                | 466 ++++++++++++++++++
>   4 files changed, 616 insertions(+)
>   create mode 100644 Documentation/guides/camera-sensor-helper.rst
>   create mode 100755 utils/measure-analogue-gain.py
>
John Cronin Aug. 11, 2026, 12:41 p.m. UTC | #2 
Hi Barnabás,

Yes — a cam-based capture path is preferable once AnalogueGain (and
fixed exposure) can be set through libcamera for the sensor under test.
v4l2-ctl in v2 is for bring-up when no helper exists yet and the
libcamera control path is not enough. Happy to document both, and to
add a cam mode in a follow-up when that works.

Thanks,
John