On Tue, May 03, 2022 at 12:14:30PM +0200, Geert Uytterhoeven wrote:
> Hi Alan,
>
> On Sat, 23 Apr 2022, Alan Stern wrote:
> > This patch adds a "gadget" bus and uses it for registering gadgets and
> > their drivers. From now on, bindings will be managed by the driver
> > core rather than through ad-hoc manipulations in the UDC core.
> >
> > As part of this change, the driver_pending_list is removed. The UDC
> > core won't need to keep track of unbound drivers for later binding,
> > because the driver core handles all of that for us.
> >
> > However, we do need one new feature: a way to prevent gadget drivers
> > from being bound to more than one gadget at a time. The existing code
> > does this automatically, but the driver core doesn't -- it's perfectly
> > happy to bind a single driver to all the matching devices on the bus.
> > The patch adds a new bitflag to the usb_gadget_driver structure for
> > this purpose.
> >
> > A nice side effect of this change is a reduction in the total lines of
> > code, since now the driver core will do part of the work that the UDC
> > used to do.
> >
> > A possible future patch could add udc devices to the gadget bus, say
> > as a separate device type.
> >
> > Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
>
> Thanks for your patch, which is now commit fc274c1e997314bf ("USB:
> gadget: Add a new bus for gadgets") in usb-next.
>
> This patch cause a regression on the Renesas Salvator-XS development
> board, as R-Car H3 has multiple USB gadget devices:
Then these gadgets ought to have distinct names in order to avoid the
conflict below:
> sysfs: cannot create duplicate filename '/bus/gadget/devices/gadget'
> CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.18.0-rc1-arm64-renesas-00074-gfc274c1e9973 #1587
> Hardware name: Renesas Salvator-X 2nd version board based on r8a77951 (DT)
> Call trace:
> dump_backtrace+0xcc/0xd8
> show_stack+0x14/0x30
> dump_stack_lvl+0x88/0xb0
> dump_stack+0x14/0x2c
> sysfs_warn_dup+0x60/0x78
> sysfs_do_create_link_sd.isra.0+0xe4/0xf0
> sysfs_create_link+0x20/0x40
> bus_add_device+0x64/0x110
> device_add+0x31c/0x850
> usb_add_gadget+0x124/0x1a0
> usb_add_gadget_udc_release+0x1c/0x50
> usb_add_gadget_udc+0x10/0x18
> renesas_usb3_probe+0x450/0x728
...
Having three gadget devices, all named "gadget", doesn't seem like a
good idea.
> After boot-up, only one gadget device is visible:
Naturally, since the first registration succeeds and the later ones fail
because they can't reuse the same name.
> root@h3-salvator-xs:~# ls -l /sys/bus/gadget/devices/
> total 0
> lrwxrwxrwx 1 root root 0 Feb 14 2019 gadget -> ../../../devices/platform/soc/e659c000.usb/gadget
> root@h3-salvator-xs:~#
>
> Reverting this patch fixes the issue.
This doesn't seem like it should be too hard to fix, although I'm not
at all familiar with the renesas-usb3 driver. Do you know who maintains
that driver? Is it you?
Alan Stern
