[PATCH] sysfs: Allow sysfs attribute files to be pollable
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>
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 392da5a..1ea5d3c 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -74,6 +74,7 @@
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_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_notify(struct kobject * k, char *dir, char *attr)
+{
+}
+
#endif /* CONFIG_SYSFS */
#endif /* _SYSFS_H_ */