Re: How to register a new "function" in configfs?

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Any pointers, please?

On Sat, Sep 11, 2021 at 8:28 PM Ajay Garg <ajaygargnsit@xxxxxxxxx> wrote:
>
> Hi Michael,
>
> Thanks for the reply.
>
> I am a bit of old-school, and would prefer things in one place only
> (in the kernel) :)
> Thus :
>
> a)
> I wish to have all the endpoints configuration/management in the
> kernel only (like done in drivers/usb/gadget/function/f_serial.c,
> drivers/usb/gadget/function/u_serial.c).
>
> b)
> Only the attributes like vendorId/productId would be in configfs, to
> help setup the device.
>
> c)
> No user-space management of kernel objects.
>
>
> Either-way, I think that my issue of "function exposure" would remain
> the same, irrespective of whether we use configfs for managing the
> kernel-objects (please correct me if I am wrong).
>
>
> Thanks again for your time, look forward to listening back !
>
>
> Thanks and Regards,
> Ajay
>
> On Sat, Sep 11, 2021 at 8:01 PM Michael Sweet <msweet@xxxxxxxxxx> wrote:
> >
> > Ajay,
> >
> > Quick question (as someone who has been down this road), do you need to do a kernel driver or could you just use the functionfs support to implement everything in userspace?  I found that path to be much easier and less error-prone (and one of these days I'm going to be contributing some documentation changes to make some things clearer...) and I was able to get my IPP-USB implementation up and running very quickly.
> >
> >
> > > On Sep 11, 2021, at 1:43 AM, Ajay Garg <ajaygargnsit@xxxxxxxxx> wrote:
> > >
> > > Hi All.
> > >
> > > As a first step, I have been able to load a gadget on configfs, which
> > > binds to the function "gser" (thus loading up the usb_f_serial module
> > > when the gadget mounts). Things work well till here.
> > >
> > > Now, I have written a brand-new gadget-side device-driver, trying to
> > > create a new function "gusb", via DECLARE_USB_FUNCTION_INIT.
> > > However, now when I try to load the gadget for binding to "gusb", I
> > > get the error that the function cannot be found.
> > >
> > > Seems that firing up a new gadget-side driver, that registers a new
> > > function via DECLARE_USB_FUNCTION_INIT, is not enough to make the new
> > > function visible across the kernel.
> > >
> > > Kindly let know what I am missing.
> > > Will be grateful for pointers.
> > >
> > >
> > > Thanks and Regards,
> > > Ajay
> > >
> >
> > ________________________
> > Michael Sweet
> >
> >
> >




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