[libcamera-devel] Compatibility with cameras

[Guido Körber]

Thank you Dave! This sounds good. Likely we will have some (hardware) things to support the persuation ;)


> Am 24.02.2022 um 17:45 schrieb Dave Stevenson <dave.stevenson at raspberrypi.com>:
> 
> On Thu, 24 Feb 2022 at 15:28, Laurent Pinchart
> <laurent.pinchart at ideasonboard.com> wrote:
>> 
>> 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.
> 
> Analogue gain appears to be there already -
> https://elixir.bootlin.com/linux/v5.16.11/source/drivers/media/i2c/ov2740.c#L590
> 
> It appears that the driver doesn't support Device Tree, only ACPI.
> It'll need a struct of_device_id defining and referenced from
> ov2740_i2c_driver.
> 
> If you're really stuck then doing the basic work should only take one
> of us about 15 minutes, so you may persuade us to do it for you. It
> does rely on you having the same external clock feeding the sensor as
> the driver is expecting (19.2MHz).
> 
>  Dave
> 
>>>> 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

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