[libcamera-devel] Compatibility with cameras

[Laurent Pinchart]

On Thu, Feb 24, 2022 at 04:22:15PM +0100, Guido Körber wrote:
> Hi Laurent,
> 
> can’t check that at the moment but will do.
> 
> The camera supposedly contains an Omnivision OV2740 sensor.

You're lucky,

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/media/i2c/ov2740.c

> I was hoping that we would only need to tell some existing driver to
> use this camera.

After a quick look at the driver, it seems you will only have to
implement support for the V4L2_CID_ANALOG_GAIN control, and for the crop
selection targets mentioned in the libcamera documentation.

> > Am 24.02.2022 um 16:12 schrieb Laurent Pinchart:
> > On Thu, Feb 24, 2022 at 04:02:58PM +0100, Guido Körber wrote:
> >> We can see a device on the I2C. (Took a bit more testing to get the
> >> hardware to really respond…)
> >> 
> >> So will we need a specific kernel driver for that camera, or is there
> >> some way to handle it via a generic driver?
> > 
> > It needs a kernel driver. Have you checked in drivers/media/i2c/ (in the
> > kernel) if the sensor you're using is already supported ? If so, some
> > work may still be needed to support all the features required by
> > libcamera (see Documentation/sensor_driver_requirements.rst), but it
> > would be much easier than writing a new driver from scratch.
> > 
> >>> Am 17.02.2022 um 17:43 schrieb Laurent Pinchart:
> >>> On Thu, Feb 17, 2022 at 05:00:23PM +0100, Guido Körber wrote:
> >>>> Is there a simple way to check if the hardware is present even if
> >>>> the camera is not detected by software?
> >>>> 
> >>>> I have set up a prototype with a hand soldered connector and would
> >>>> like to know if I did all the wiring correct.
> >>> 
> >>> You can use i2cdetect and i2cget ([1]) to talk to the sensor. You may
> >>> need to first enable power by toggling the corresponding GPIO, which can
> >>> also be done from userspace ([2]). Checking video transmission is more
> >>> difficult, you will need to get at least the kernel driver for the
> >>> sensor and Unicam up and running.
> >>> 
> >>> [1] https://manpages.debian.org/unstable/i2c-tools/i2cdetect.8.en.html
> >>> [2] https://manpages.debian.org/experimental/gpiod/gpioset.1.en.html
> >>> 
> >>>>> Am 17.02.2022 um 14:09 schrieb Kieran Bingham:
> >>>>> Quoting Guido Körber (2022-02-17 13:04:18)
> >>>>>> 
> >>>>>> I want to use libcamera on Raspberry with a camera that is not
> >>>>>> explicitly supported by libcamera but does generic CSI-2. Will this
> >>>>>> work, or do I need a camera specific plugin or something else?
> >>>>> 
> >>>>> You will likely need to make sure you have a relevant kernel driver, and
> >>>>> may likely need to do some updates to libcamera, to manage the
> >>>>> CameraSensorHelper classes.
> >>>>> 
> >>>>> You might also then want to follow the Raspberry Pi ISP tuning
> >>>>> procedures.
> >>>>> 
> >>>>> https://datasheets.raspberrypi.com/camera/raspberry-pi-camera-guide.pdf
> >>>>> 
> >>>>> But yes, you should be able to get it to work.

-- 
Regards,

Laurent Pinchart