Failure to Assign UDC to ConfigFS Gadget

Failure to Assign UDC to ConfigFS Gadget

[Sid Spry]

Hi, I'm just following these slides: https://events.static.linuxfound.org/sites/events/files/slides/USB%20Gadget%20Configfs%20API_0.pdf

On page 18 I need to assign the UDC. On my version of Debian (repackaged by Armbian, with my own kernel and modules) there is no device in /sys/class/udc as expected, but there is a link that resolves to a device:

# stat /sys/class/udc/musb-hdrc.1.auto
  File: /sys/class/udc/musb-hdrc.1.auto -> ../../devices/platform/soc/1c19000.usb/musb-hdrc.1.auto/udc/musb-hdrc.1.auto

If I try to assign the UDC using the string 1c19000.usb I get:

# echo "1c19000.usb" > UDC                                       
bash: echo: write error: No such device

It's at this point I'm lost. I appreciate any help.

Cheers!

RE: Failure to Assign UDC to ConfigFS Gadget

[Gopal, Saranya]

Hi Sid,

> # stat /sys/class/udc/musb-hdrc.1.auto
>   File: /sys/class/udc/musb-hdrc.1.auto ->
> ../../devices/platform/soc/1c19000.usb/musb-hdrc.1.auto/udc/musb-
> hdrc.1.auto
> 
> If I try to assign the UDC using the string 1c19000.usb I get:
> 
> # echo "1c19000.usb" > UDC
> bash: echo: write error: No such device
> 
> It's at this point I'm lost. I appreciate any help.

You need to give the exact name of UDC as present in /sys/class/udc.
So, try this:
echo "musb-hdrc.1.auto" > UDC

Thanks,
Saranya

> Cheers!

Re: Failure to Assign UDC to ConfigFS Gadget

[Sid Spry]

Ah, thanks. I actually tried that, but must have made a typo a couple times in a row. At least now I get a kernel bug printout!

On Wed, Apr 22, 2020, at 10:28 PM, Gopal, Saranya wrote:
> Hi Sid,
> 
> > # stat /sys/class/udc/musb-hdrc.1.auto
> > File: /sys/class/udc/musb-hdrc.1.auto ->
> > ../../devices/platform/soc/1c19000.usb/musb-hdrc.1.auto/udc/musb-
> > hdrc.1.auto
> > 
> > If I try to assign the UDC using the string 1c19000.usb I get:
> > 
> > # echo "1c19000.usb" > UDC
> > bash: echo: write error: No such device
> > 
> > It's at this point I'm lost. I appreciate any help.
> 
> You need to give the exact name of UDC as present in /sys/class/udc.
> So, try this:
> echo "musb-hdrc.1.auto" > UDC
> 
> Thanks,
> Saranya
> 
> > Cheers!
>