[libcamera-devel] [PATCH] libipa: Add CameraSensorHelper for OV13858

[Dave Stevenson]

On Wed, 30 Jun 2021 at 12:26, Jean-Michel Hautbois
<jeanmichel.hautbois at ideasonboard.com> wrote:
>
> Hi Kieran,
>
> Thanks for the patch.
>
> On 30/06/2021 13:21, Kieran Bingham wrote:
> > Extend the CameraSensorHelper factory with support for an
> > OV13858 sensor as found in the Soraka Chromebook.
> >
> > Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > ---
> >  src/ipa/libipa/camera_sensor_helper.cpp | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git a/src/ipa/libipa/camera_sensor_helper.cpp b/src/ipa/libipa/camera_sensor_helper.cpp
> > index 23335ed66b02..8e95b8b10102 100644
> > --- a/src/ipa/libipa/camera_sensor_helper.cpp
> > +++ b/src/ipa/libipa/camera_sensor_helper.cpp
> > @@ -313,6 +313,20 @@ public:
> >  };
> >  REGISTER_CAMERA_SENSOR_HELPER("ov5693", CameraSensorHelperOv5693)
> >
> > +/**
> > + * \class CameraSensorHelperOv13858
> > + * \brief Create and give helpers for the ov13858 sensor
> > + */
>
> As proposed by Laurent, I have a patch which (among other things)
> removes the Doxygen comments for the sub-classes as it is not really
> needed: https://patchwork.libcamera.org/patch/12736/
>
> > +class CameraSensorHelperOv13858 : public CameraSensorHelper
> > +{
> > +public:
> > +     CameraSensorHelperOv13858()
> > +     {
> > +             analogueGainConstants_ = { AnalogueGainLinear, 1, 0, 0, 256 };
>
> This is based on minimum, maximum and step value, as you don't have the
> datasheet...

OV13850 appears to be a very similar 10bit 4224x3136 sensor, and there
is a datasheet online at
http://download.t-firefly.com/product/RK3288/Docs/Peripherals/OV13850%20datasheet/Sensor_OV13850-G04A_OmniVision_SpecificationV1.pdf

It matches the driver with analogue gain being registers 0x3508/9, and
confirms that the "Low 4 bits are fraction bits which are not
supported and should always be 0".
It's making some assumptions, but seems a reasonable match.

 Dave

> That's something we should be thinking about: how to be sure of the
> values when we don't have the datasheet.
> A tuning code which would set the gains from min to max and compare the
> raw pixel values from one gain to another to deduce a linear (or not)
> relationship ?
>
> > +     }
> > +};
> > +REGISTER_CAMERA_SENSOR_HELPER("ov13858", CameraSensorHelperOv13858)
> > +
> >  } /* namespace ipa */
> >
> >  } /* namespace libcamera */
> >