UVC (USB Video Class) on CM3

Cyril_Nick_Engmann · March 26, 2024, 4:49pm

I am currently developing on the most recent release of radxa-build for the cm3-io board

Confirmed that kernel has the necessary flags enabled for UVC

CONFIG_USB_LIBCOMPOSITE=y
CONFIG_USB_CDC_COMPOSITE=m
CONFIG_USB_F_UVC=y
CONFIG_USB_CONFIGFS_F_UVC=y

So I’m working on enabling UVC functionality utilizing the micro OTG port in peripheral mode.

Using rsetup I enabled the peripheral mode USB overlay, and from rsetup I found radxa-otgutils

github.com

radxa-pkg/radxa-otgutils/blob/main/src/radxa-otgutils

#!/bin/bash -e

lock_udc()
{
    configfs_make
    exec 100<"/sys/kernel/config/usb_gadget/$UDC"
    flock 100
}

unlock_udc()
{
    exec 100<&-
}

enable_udc()
{
    if [[ -n $(cat "/sys/kernel/config/usb_gadget/$UDC/UDC") ]];
    then
        echo "" > "/sys/kernel/config/usb_gadget/$UDC/UDC"
    fi

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Using that as a reference, I built a script, radxa-uvcutils.sh, to try to enable UVC by forwarding the /dev/video0 interface from another program.

gist.github.com

https://gist.github.com/NickEngmann/c0af916fc6c6ad5258842503fffd4c0f

gistfile1.txt

#!/bin/bash -e

lock_udc()
{
    configfs_make
    exec 100<"/sys/kernel/config/usb_gadget/$UDC"
    flock 100
}

unlock_udc()

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I’m consistently running into errors initialing the UVC device after setting up the directory structure and running the enable_udc() function, which results in dmesg errors

[  157.471232] configfs-gadget gadget: uvc: uvc_function_bind()
[  157.471253] configfs-gadget gadget: uvc: overriding streaming_maxpacket to 1024
[  157.471290] udc fcc00000.dwc3: failed to start fcc00000.dwc3: -19

I am wondering if any community member or Radxa engineer has dealt with similar issues and managed to create a functioning solution