hi, "Andrew P. Lentvorski" <bsder@xxxxxxxxxxx> writes: > On 1/15/20 7:14 AM, Alan Stern wrote: > >> I don't think any earlier messages in this thread made it through the >> mailing list, but this one definitely did. > > Yay! I also saw this one in the archives so I was hopeful. > >>>> I've been trying to set "iInterface" in my usb gadget to a specific >>>> string, but I simply can't find a way to make configfs accept this. iInterface is not a string. It's the index to a string descriptor table. >>>> When I set my gadget up on my Beaglebone Black (uname -a: Linux >>>> beaglebone 4.14.108-ti-r113 #1 SMP PREEMPT Wed Jul 31 00:01:10 UTC >>>> 2019 armv7l GNU/Linux). >>>> >>>> I get (output from lsusb): >>>> >>>> iInterface 5 HID Interface >>>> >>>> >>>> But I want it to be something like: >>>> >>>> iInterface 4 LPC-LINK2 CMSIS-DAP V5.224 Why? Oh, you want your beaglebone to behave as a CMSIS-DAP to trick some other SW? Do we need to support that upstream, though? It seems like this is a one-off thing. Does anybody else need to configure interface string descriptor? >> Then maybe you need to fix f_hid.c. Or maybe configfs isn't meant to >> allow the user to specify these string index values (I don't know any >> of the configfs details). > > That's kind of my problem in that I was hoping to get someone far more > knowledegable than me to at least flag these before attacking it: > > A) I didn't overlook something stupid and this really is hardwired with > no way to change it (either in configfs or ... some other? kernel mechanism) yes, it really is hardwired > B) This is an *actual* bug. Not a bug, just was never a requirement. > C) This is an actual bug *that should be fixed* and isn't that way > intentionally for some Linux reason. Up until now, it has been intentional. Currently, I don't see a need to change it. I may be persuaded otherwise, but I need to see arguments other than "I want to trick some SW into thinking I'm something else". > D) This is actually the right place to fix it. Obviously there is going > to be something at the configfs level, too, and I have *zero* idea where > to start looking for that. drivers/usb/gadget/configfs.c, look for GS_STRINGS_RW(). Note, also, that you should *not* allow for strings to be changed after the device has been enumerated. -- balbi
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