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Commit 7f847dd3 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Greg Kroah-Hartman
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debugfs: improve DEFINE_DEBUGFS_ATTRIBUTE for !CONFIG_DEBUG_FS 



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: c6468808 ("debugfs: add support for self-protecting attribute file fops")
Fixes: df2294fb ("intel_pmc_core: Convert to DEFINE_DEBUGFS_ATTRIBUTE")
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
[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: default avatarNicolai Stange <nicstange@gmail.com>
Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent edbbf994

include/linux/debugfs.h

+27 −17
Original line number Diff line number Diff line
@@ -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)