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SubjectRe: [PATCH 4/4] USB: gadget: Add a new bus for gadgets
 	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@rowland.harvard.edu>

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:

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
platform_probe+0x64/0xd0
really_probe+0x100/0x2a0
__driver_probe_device+0x74/0xd8
driver_probe_device+0x3c/0xe0
__driver_attach+0x80/0x110
bus_for_each_dev+0x6c/0xc0
driver_attach+0x20/0x28
bus_add_driver+0x138/0x1e0
driver_register+0x60/0x110
__platform_driver_register+0x24/0x30
renesas_usb3_driver_init+0x18/0x20
do_one_initcall+0x15c/0x31c
kernel_init_freeable+0x2f0/0x354
kernel_init+0x20/0x120
ret_from_fork+0x10/0x20
renesas_usb3: probe of ee020000.usb failed with error -17
...
renesas_usbhs: probe of e6590000.usb failed with error -17

After boot-up, only one gadget device is visible:

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.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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

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