[libcamera-devel] How to detect camera after power on the raspberryPi.

[Dave Stevenson]

Hi Nomura

On Mon, 19 Oct 2020 at 10:38, <tetsuya.nomura at soho-enterprise.com> wrote:
>
> Dear Sirs.
>
> May I have your favor about initialization of the RaspberryPi and the camera?
>
> I'm now evaluating the camera extension board of FPD LINK III technology to extend the camera cable for 2~3m from the RaspberryPi.
> https://soho-enterprise.com/2020/10/11/post-866/
>
> This board can pass the I2C communication to IMX219 after configuring the transceiver chip,
> However, after configuration and run the qcam, it seems the qcam program does not detect the IMX219
> And I cannot start the camera even I designate the image sensor name.

The Pi kernel driver for imx219 probes the sensor driver as the module
loads, which is only a few seconds into boot if you've added
"dtoverlay=imx219" into config.txt. No or incorrect response from the
sensor and it won't create the /dev/video0 device nodes. If your
transceivers need some form of configuration then I suspect this has
not happened by this point.

The correct approach is probably to have a driver for your transceiver
in the kernel driver chain, ie imx219 -> transceiver -> Unicam,
however that opens a big can of worms over configuration as it forces
the use of the Media Controller API to configure each link
independently.

One workaround would be to remove "dtoverlay=imx219" from config.txt
and use dynamic device tree overlay loading to load the relevant
modules later in boot. "sudo dtoverlay imx219" should do that for you.
The niggle is that when done from config.txt the firmware fixes up the
camera shutdown GPIO to match the platform (it moves GPIOs between
different variants of the Pi). If loading dynamically then this can't
happen, and you'll need to fix up the regulator shutdown line manually
[1] (assuming that it is actually controllable at the other end of the
FPD Link)

  Dave

[1] (https://github.com/raspberrypi/linux/blob/rpi-5.4.y/arch/arm/boot/dts/overlays/imx219-overlay.dts#L77)

> I can start the IMX219, get the RAW image by our own program and see the image.
> Then if qcam can send the necessary command to IMX219 when start running the qcam,
> I think I can see the image through qcam program.
>
> It would be great if you could give us an advice to solve it.
> I appreciate your kind help in advance.
>
> Best Regards,
>
> NOMURA
>
> ================================
>   Tetsuya NOMURA
> ================================
>  Soho Enterprise Ltd.
>  4-11-26 Gent BLDG 2F, Asahi-cho, Atsugi-shi,
>  Kanagawa, Japan  243-0014
>  URL: https://soho-enterprise.com
>  Mail: tetsuya.nomura at soho-enterprise.com
>  Phone: +81-90-1839-1135
> ================================
>
>
>
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