Re: Documentation for Raw USB ConfigFS

["Sid Spry" <sid@aeam.us>]

On Thu, May 14, 2020, at 8:05 PM, Peter Chen wrote:
> 
> > >
> > > Would you please let ECM gadget work first at your board, then let
> > > f_fs work using test application (you need to compile both host and
> > > device application for it). After that, you may have more precise
> > > concept for Linux USB gadget framework.
> > >
> > 
> > I don't see anything that harmonizes preexsting function usage with specifying
> > custom endpoints.
> > 
> > I've gotten the ECM gadget, and then the ECM gadget via ffs working. I've read
> > through the ffs test but I don't see any way to assign functionality to the endpoints.
> > The example seems to transport raw data via a bulk endpoint. I know enough to
> > instead assign an isochronous endpoint to the UDC and transfer via that, but I don't
> > want it to be the *only* functionality the device offers.
> > 
> > Are you saying I can assign the ECM gadget via ffs and then add another driver
> > after the fact? 
> 
> ffs (f_fs.c) is used for customized function, other functions, like ECM (f_ecm.c)
> and Mass Storage (f_mass_storage.c) are used for certain function. You could
> use configfs (like you have done below) to put customized function and certain functions
> into one configuration, and let the host see them at the same time. Do your
> real requirement is one customized function and one ECM function in one USB gadget?
> If it is, below is the example to combine f_fs, mass_storage, and NCM together.
> 
> cd /sys/kernel/config/usb_gadget
> cd g1
> echo "0x1d6b" > idVendor
> echo "0x0105" > idProduct
> mkdir /dev/usb-ffs
> mkdir functions/ffs.usb
> mount -t functionfs usb /dev/usb-ffs
> ln -s functions/ffs.usb configs/c.1
> /home/root/usb_test/ffs_test/ffs-test & /* your own test application */
> while [ ! -e /dev/usb-ffs/ep1 ]
> do
>  echo "."
>  sleep 1;
> done
> mkdir functions/ncm.0 
> ln -s functions/ncm.0 configs/c.1 
> mkdir functions/mass_storage.0
> ln -s functions/mass_storage.0 configs/c.1
> echo $FILE > functions/mass_storage.0/lun.0/file 
> 
> Peter 
> 

Hi Peter, thanks for the advice. I realized I was confusing FunctionFS and ConfigFS a little while after I sent my message and saw the FFS configuration in the ConfigFS documentation.

And yes, I need ECM/NCM (one is newer and faster, will go look it up again) and my custom function. I may also include a serial port.

I have been having issues creating any file called "ffs.${id}" in the gadget directory. It fails with device or resource busy. I assume this means I have misconfigured it, but I am copying your example; or missing the driver, but I have ensured it is there.[1] I have also tried ensuring the ffs function is added first. Any pointers?


[1]: I actually did not have CONFIG_USB_CONFIGFS_F_FS nor F_NCM/ECM set however the necessary code seemed to have been pulled in some other way and the modules were available. They were loaded, and as explained my shell-based configfs code worked. They are set now and the problem persists.