linux-kernel - Re: [PATCH 4/4] USB: gadget: Add a new bus for gadgets

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Message-ID: <CAMuHMdVi6jCi=tRBNjBodVcA48ygiqPACQcmHx+1HRYnArJ9tQ@mail.gmail.com>
Date:   Mon, 9 May 2022 16:42:01 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     Felipe Balbi <balbi@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        USB mailing list <linux-usb@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Subject: Re: [PATCH 4/4] USB: gadget: Add a new bus for gadgets

Hi Alan,

On Mon, May 9, 2022 at 4:15 PM Alan Stern <stern@...land.harvard.edu> wrote:
> On Mon, May 09, 2022 at 09:46:25AM +0200, Geert Uytterhoeven wrote:
> > > Geert:
> > >
> > > Can you test the patch below?  It ought to fix the problem (although it
> >
> > Thanks!
> >
> > root@...salvator-xs:~# ls -l /sys/bus/gadget/devices/
> > total 0
> > lrwxrwxrwx 1 root root 0 Feb 14  2019 gadget.0 ->
> > ../../../devices/platform/soc/e659c000.usb/gadget.0
> > lrwxrwxrwx 1 root root 0 Feb 14  2019 gadget.1 ->
> > ../../../devices/platform/soc/ee020000.usb/gadget.1
> > lrwxrwxrwx 1 root root 0 Feb 14  2019 gadget.2 ->
> > ../../../devices/platform/soc/e6590000.usb/gadget.2
> >
> > Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>
> >
> > LGTM, so
> > Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
>
> Thanks!
>
> > > might end up causing other problems down the line...)
> >
> > Can you please elaborate? I'm not too familiar with UBS gadgets.
>
> I was concerned about the fact that changing the name of a file,
> directory, or symbolic link in sysfs means changing a user API, and so
> it might cause some existing programs to fail.  That would be a
> regression.
>
> Perhaps the best way to work around the problem is to leave the name set
> to "gadget" if the ID number is 0, while adding the ID number on to the
> name if the value is > 0.  What do you think?

Oh, you mean the "gadget.N" subdirs, which are the targets of the
symlinks above? These were indeed named "gadget" before.

Would it be possible to append the ".N" suffixes only to the actual
symlinks, while keeping the target directory names unchanged?
E.g. /sys/bus/gadget/devices/gadget.0 ->
../../../devices/platform/soc/e659c000.usb/gadget

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds