From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ACEE6C433EF for ; Tue, 3 May 2022 14:54:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237465AbiECO5q (ORCPT ); Tue, 3 May 2022 10:57:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51436 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236357AbiECO5p (ORCPT ); Tue, 3 May 2022 10:57:45 -0400 Received: from netrider.rowland.org (netrider.rowland.org [192.131.102.5]) by lindbergh.monkeyblade.net (Postfix) with SMTP id CE2FF38D8F for ; Tue, 3 May 2022 07:54:11 -0700 (PDT) Received: (qmail 1087789 invoked by uid 1000); 3 May 2022 10:54:10 -0400 Date: Tue, 3 May 2022 10:54:10 -0400 From: Alan Stern To: Geert Uytterhoeven Cc: Felipe Balbi , Greg KH , USB mailing list , linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/4] USB: gadget: Add a new bus for gadgets Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org 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 > > 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