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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9EFEEC46460 for ; Fri, 31 May 2019 05:45:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8153F263BE for ; Fri, 31 May 2019 05:45:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726721AbfEaFo7 (ORCPT ); Fri, 31 May 2019 01:44:59 -0400 Received: from mga18.intel.com ([134.134.136.126]:41385 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725988AbfEaFo6 (ORCPT ); Fri, 31 May 2019 01:44:58 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 May 2019 22:44:58 -0700 X-ExtLoop1: 1 Received: from pipin.fi.intel.com (HELO pipin) ([10.237.72.175]) by orsmga003.jf.intel.com with ESMTP; 30 May 2019 22:44:55 -0700 From: Felipe Balbi To: Chunfeng Yun Cc: Greg Kroah-Hartman , Matthias Brugger , Randy Dunlap , linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [v3 PATCH] usb: create usb_debug_root for gadget only In-Reply-To: <1559201499.8487.40.camel@mhfsdcap03> References: <87k1ebj8vt.fsf@linux.intel.com> <1559201499.8487.40.camel@mhfsdcap03> Date: Fri, 31 May 2019 08:44:55 +0300 Message-ID: <87sgsv2n54.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Chunfeng Yun writes: > Hi Felipe, > On Tue, 2019-05-28 at 11:11 +0300, Felipe Balbi wrote: >> Hi, >> >> Chunfeng Yun writes: >> > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c >> > index 7fcb9f782931..88b3ee03a12d 100644 >> > --- a/drivers/usb/core/usb.c >> > +++ b/drivers/usb/core/usb.c >> > @@ -1190,7 +1190,7 @@ EXPORT_SYMBOL_GPL(usb_debug_root); >> > >> > static void usb_debugfs_init(void) >> > { >> > - usb_debug_root = debugfs_create_dir("usb", NULL); >> > + usb_debug_root = debugfs_create_dir(USB_DEBUG_ROOT_NAME, NULL); >> > debugfs_create_file("devices", 0444, usb_debug_root, NULL, >> > &usbfs_devices_fops); >> > } >> >> might be a better idea to move this to usb common. Then have a function >> which can be called by both host and gadget to maybe create the >> directory: >> >> static struct dentry *usb_debug_root; >> >> struct dentry *usb_debugfs_init(void) >> { >> if (!usb_debug_root) >> usb_debug_root = debugfs_create_dir("usb", NULL); >> >> return usb_debug_root; >> } >> >> >> Then usb core would be updated to something like: >> >> static void usb_core_debugfs_init(void) >> { >> struct dentry *root = usb_debugfs_init(); >> >> debugfs_create_file("devices", 0444, root, NULL, &usbfs_devices_fops); >> } >> > I find a problem when move usb_debugfs_init() and usb_debugfs_cleanup() > into usb common, it's easy to create "usb" directory, but difficult to > cleanup it: > > common/common.c > > struct dentry *usb_debugfs_init(void) > { > if (!usb_debug_root) > usb_debug_root = debugfs_create_dir("usb", NULL); > > return usb_debug_root; > } > > void usb_debugfs_cleanup(void) > { > debugfs_remove_recursive(usb_debug_root); > usb_debug_root = NULL; > } > > core/usb.c > > static void usb_core_debugfs_init(void) > { > struct dentry *root = usb_debugfs_init(); > > debugfs_create_file("devices", 0444, root, NULL, > &usbfs_devices_fops); > } > > static int __init usb_init(void) > { > ... > usb_core_debugfs_init(); > ... > } > > static void __exit usb_exit(void) > { > ... > usb_debugfs_cleanup(); > // will be error, gadget may use it. > ... > } > > gadget/udc/core.c > > static int __init usb_udc_init(void) > { > ... > usb_debugfs_init(); > ... > } > > static void __exit usb_udc_exit(void) > { > ... > usb_debugfs_cleanup(); > // can't cleanup in fact, usb core may use it. > } > > How to handle this case? introduce a reference count? do you have any > suggestion? I guess a simple refcount is the way to go: struct dentry *usb_debugfs_init(void) { if (!usb_debug_root) usb_debug_root = debugfs_create_dir("usb", NULL); usb_debug_root_refcnt++; return usb_debug_root; } void usb_debugfs_cleanup(void) { if (!(--usb_debug_root_refcnt)) { debugfs_remove_recursive(usb_debug_root); usb_debug_root = NULL; } } Or something along those lines -- balbi