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[PATCH] sysfs: Allow sysfs attribute files to be pollable

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It works like this:
  Open the file
  Read all the contents.
  Call poll requesting POLLERR or POLLPRI (so select/exceptfds works)
  When poll returns,
     close the file and go to top of loop.
   or lseek to start of file and go back to the 'read'.

Events are signaled by an object manager calling
   sysfs_notify(kobj, dir, attr);

If the dir is non-NULL, it is used to find a subdirectory which
contains the attribute (presumably created by sysfs_create_group).

This has a cost of one int  per attribute, one wait_queuehead per kobject,
one int per open file.

The name "sysfs_notify" may be confused with the inotify
functionality.  Maybe it would be nice to support inotify for sysfs
attributes as well?

This patch also uses sysfs_notify to allow /sys/block/md*/md/sync_action
to be pollable

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
NeilBrown
2006-03-20 17:53:53 +11:00
committed by Greg Kroah-Hartman
parent f043ca43c1
commit 4508a7a734
7 changed files with 88 additions and 0 deletions
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2
include/linux/kobject.h
View File

@@ -24,6 +24,7 @@
#include <linux/rwsem.h>
#include <linux/kref.h>
#include <linux/kernel.h>
#include <linux/wait.h>
#include <asm/atomic.h>
#define KOBJ_NAME_LEN 20
@@ -56,6 +57,7 @@ struct kobject {
struct kset * kset;
struct kobj_type * ktype;
struct dentry * dentry;
wait_queue_head_t poll;
};
extern int kobject_set_name(struct kobject *, const char *, ...)

6
include/linux/sysfs.h
View File

@@ -74,6 +74,7 @@ struct sysfs_dirent {
umode_t s_mode;
struct dentry * s_dentry;
struct iattr * s_iattr;
atomic_t s_event;
};
#define SYSFS_ROOT 0x0001
@@ -117,6 +118,7 @@ int sysfs_remove_bin_file(struct kobject * kobj, struct bin_attribute * attr);
int sysfs_create_group(struct kobject *, const struct attribute_group *);
void sysfs_remove_group(struct kobject *, const struct attribute_group *);
void sysfs_notify(struct kobject * k, char *dir, char *attr);
#else /* CONFIG_SYSFS */
@@ -185,6 +187,10 @@ static inline void sysfs_remove_group(struct kobject * k, const struct attribute
;
}
static inline void sysfs_notify(struct kobject * k, char *dir, char *attr)
{
}
#endif /* CONFIG_SYSFS */
#endif /* _SYSFS_H_ */