I want to create a USB gadget with a raspberry pi zero 2W. I’m starting with imitating a webcam I already have to see how much of this I can figure out. I’ve used the online documentation and a couple AI bots to get this far quickly, but I’m hung up on a ln command. It’s telling me “ln: failed to create symbolic link ‘configs/c.1/uvc.usb0’: No such file or directory” when trying to create the link. This makes no sense to me though. I’m trying to create the link, of course it doesn’t exist yet. That’s what that command is supposed to do.

I’ve confirmed this problem in alpine linux and raspbian lite.

Below is the little script I have so far just to create the device:

#!/bin/bash
modprobe libcomposite
cd /sys/kernel/config/usb_gadget/
mkdir -p fauxcam
cd fauxcam
echo 0x046d > idVendor  # Logitech Vendor ID
echo 0x094b > idProduct # Brio 105 Product ID
echo 0x0200 > bcdUSB
echo 0x9914 > bcdDevice
mkdir -p strings/0x409
echo "111111111111" > strings/0x409/serialnumber
echo "Brio 105" > strings/0x409/product
mkdir -p configs/c.1/strings/0x409
echo "UVC Configuration" > configs/c.1/strings/0x409/configuration
echo 250 > configs/c.1/MaxPower
mkdir -p functions/uvc.usb0
ln -s functions/uvc.usb0 configs/c.1/
echo "usb0" > UDC
  • gnuhaut@lemmy.ml
    1·
    1 hour ago

    IDK how all that works but I will say that the result of this would (in a normal filesystem) create a link named configs/c.1/uvc.usb0 yes, but that link would point to functions/uvc.usb0 relative to its own dir. This doesn’t exist and your symlink would be broken, presumably the special file system there doesn’t like that.

    • dafta@lemmy.blahaj.zoneEnglish
      1·
      41 minutes ago

      Normally, you’d be right, but this special filesystem doesn’t care about that. I’ve done similar with different gadgets so many times, always with relativr symlinks, sometimes directly from the root of the special filesystem, sometimes from the gadgets own subdirectory, and it just works.

  • dafta@lemmy.blahaj.zoneEnglish
    1·
    5 hours ago

    Hey, you need to also modprobe usb_f_uvc at the beggining, right after modprobe libcomposite

    • muusemuuse@lemm.eeOPEnglish
      1·
      2 hours ago

      no change

      ln: failed to create symbolic link 'configs/c.1/uvc.usb0': No such file or directory
./fauxcam-gadget.sh: line 19: echo: write error: Device or resource busy