From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752658AbcJTUIW (ORCPT ); Thu, 20 Oct 2016 16:08:22 -0400 Received: from mail-lf0-f67.google.com ([209.85.215.67]:34492 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750974AbcJTUIT (ORCPT ); Thu, 20 Oct 2016 16:08:19 -0400 From: Nicolai Stange To: Greg Kroah-Hartman Cc: Arnd Bergmann , Andy Shevchenko , Rajneesh Bhardwaj , Darren Hart , linux-kernel@vger.kernel.org, Nicolai Stange Subject: [PATCH v2] debugfs: improve DEFINE_DEBUGFS_ATTRIBUTE for !CONFIG_DEBUG_FS Date: Thu, 20 Oct 2016 22:07:53 +0200 Message-Id: <20161020200753.3252-1-nicstange@gmail.com> X-Mailer: git-send-email 2.10.1 In-Reply-To: <5795991.0oAm3xDhR2@wuerfel> References: <5795991.0oAm3xDhR2@wuerfel> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Arnd Bergmann The slp_s0_residency_usec debugfs file currently uses DEFINE_DEBUGFS_ATTRIBUTE(), but that macro cannot really be used to define files outside of the debugfs code, as it has no reference to the get/set functions if CONFIG_DEBUG_FS is not defined: drivers/platform/x86/intel_pmc_core.c:80:12: error: ‘pmc_core_dev_state_get’ defined but not used [-Werror=unused-function] This fixes the macro to always contain the reference, and instead rely on the stubbed-out debugfs_create_file to not actually refer to its arguments so the compiler can still drop the reference. This works because the attribute definition is always 'static', and the dead-code removal silently drops all static symbols that are not used. Fixes: c64688081490 ("debugfs: add support for self-protecting attribute file fops") Fixes: df2294fb6428 ("intel_pmc_core: Convert to DEFINE_DEBUGFS_ATTRIBUTE") Signed-off-by: Arnd Bergmann [nicstange@gmail.com: Add dummy implementations of debugfs_attr_read() and debugfs_attr_write() in order to protect against possibly broken dead code elimination and to improve readability. Correct CONFIG_DEBUGFS_FS -> CONFIG_DEBUG_FS typo in changelog.] Signed-off-by: Nicolai Stange --- Compile-tested on top of next-20161020 with gcc-4.9.0 and gcc-6.2.1, CONFIG_INTEL_PMC_CORE=y and both, CONFIG_DEBUG_FS=n and CONFIG_DEBUG_FS=y. I verified that there isn't anything in the intel_pmc_core.o that shouldn'tbe there with CONFIG_DEBUG_FS=n. Changes to v1: - Add dummy implementations of debugfs_attr_read()/debugfs_attr_write() for the CONFIG_DEBUG_FS=n case. - Fix a typo in the changelog. include/linux/debugfs.h | 44 +++++++++++++++++++++++++++----------------- 1 file changed, 27 insertions(+), 17 deletions(-) diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h index 4d3f0d1..1b413a9 100644 --- a/include/linux/debugfs.h +++ b/include/linux/debugfs.h @@ -62,6 +62,21 @@ static inline const struct file_operations *debugfs_real_fops(struct file *filp) return filp->f_path.dentry->d_fsdata; } +#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt) \ +static int __fops ## _open(struct inode *inode, struct file *file) \ +{ \ + __simple_attr_check_format(__fmt, 0ull); \ + return simple_attr_open(inode, file, __get, __set, __fmt); \ +} \ +static const struct file_operations __fops = { \ + .owner = THIS_MODULE, \ + .open = __fops ## _open, \ + .release = simple_attr_release, \ + .read = debugfs_attr_read, \ + .write = debugfs_attr_write, \ + .llseek = generic_file_llseek, \ +} + #if defined(CONFIG_DEBUG_FS) struct dentry *debugfs_create_file(const char *name, umode_t mode, @@ -99,21 +114,6 @@ ssize_t debugfs_attr_read(struct file *file, char __user *buf, ssize_t debugfs_attr_write(struct file *file, const char __user *buf, size_t len, loff_t *ppos); -#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt) \ -static int __fops ## _open(struct inode *inode, struct file *file) \ -{ \ - __simple_attr_check_format(__fmt, 0ull); \ - return simple_attr_open(inode, file, __get, __set, __fmt); \ -} \ -static const struct file_operations __fops = { \ - .owner = THIS_MODULE, \ - .open = __fops ## _open, \ - .release = simple_attr_release, \ - .read = debugfs_attr_read, \ - .write = debugfs_attr_write, \ - .llseek = generic_file_llseek, \ -} - struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry, struct dentry *new_dir, const char *new_name); @@ -233,8 +233,18 @@ static inline void debugfs_use_file_finish(int srcu_idx) __releases(&debugfs_srcu) { } -#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt) \ - static const struct file_operations __fops = { 0 } +static inline ssize_t debugfs_attr_read(struct file *file, char __user *buf, + size_t len, loff_t *ppos) +{ + return -ENODEV; +} + +static inline ssize_t debugfs_attr_write(struct file *file, + const char __user *buf, + size_t len, loff_t *ppos) +{ + return -ENODEV; +} static inline struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry, struct dentry *new_dir, char *new_name) -- 2.10.1