Merge branch 'upstream-linus' of master.kernel.org:/pub/scm/linux/kernel/git/jgarzik...

[linux-2.6-omap-h63xx.git] / fs / sysfs / file.c

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index f1cb1ddde511d7db0978ebc9bb7c7e3feb453394..95c165101c98d16e7a6e537ff6b54a2a95b6ccc2 100644 (file)
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -6,6 +6,7 @@
 #include <linux/fsnotify.h>
 #include <linux/kobject.h>
 #include <linux/namei.h>
+#include <linux/poll.h>
 #include <asm/uaccess.h>
 #include <asm/semaphore.h>
 
@@ -57,6 +58,7 @@ struct sysfs_buffer {
        struct sysfs_ops        * ops;
        struct semaphore        sem;
        int                     needs_read_fill;
+       int                     event;
 };
 
 
@@ -72,6 +74,7 @@ struct sysfs_buffer {
  */
 static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
 {
+       struct sysfs_dirent * sd = dentry->d_fsdata;
        struct attribute * attr = to_attr(dentry);
        struct kobject * kobj = to_kobj(dentry->d_parent);
        struct sysfs_ops * ops = buffer->ops;
@@ -83,6 +86,7 @@ static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer
        if (!buffer->page)
                return -ENOMEM;
 
+       buffer->event = atomic_read(&sd->s_event);
        count = ops->show(kobj,attr,buffer->page);
        buffer->needs_read_fill = 0;
        BUG_ON(count > (ssize_t)PAGE_SIZE);
@@ -153,8 +157,8 @@ sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
                if ((retval = fill_read_buffer(file->f_dentry,buffer)))
                        goto out;
        }
-       pr_debug("%s: count = %d, ppos = %lld, buf = %s\n",
-                __FUNCTION__,count,*ppos,buffer->page);
+       pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
+                __FUNCTION__, count, *ppos, buffer->page);
        retval = flush_read_buffer(buffer,buf,count,ppos);
 out:
        up(&buffer->sem);
@@ -186,6 +190,9 @@ fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t
                count = PAGE_SIZE - 1;
        error = copy_from_user(buffer->page,buf,count);
        buffer->needs_read_fill = 1;
+       /* if buf is assumed to contain a string, terminate it by \0,
+          so e.g. sscanf() can scan the string easily */
+       buffer->page[count] = 0;
        return error ? -EFAULT : count;
 }
 
@@ -348,12 +355,84 @@ static int sysfs_release(struct inode * inode, struct file * filp)
        return 0;
 }
 
+/* Sysfs attribute files are pollable.  The idea is that you read
+ * the content and then you use 'poll' or 'select' to wait for
+ * the content to change.  When the content changes (assuming the
+ * manager for the kobject supports notification), poll will
+ * return POLLERR|POLLPRI, and select will return the fd whether
+ * it is waiting for read, write, or exceptions.
+ * Once poll/select indicates that the value has changed, you
+ * need to close and re-open the file, as simply seeking and reading
+ * again will not get new data, or reset the state of 'poll'.
+ * Reminder: this only works for attributes which actively support
+ * it, and it is not possible to test an attribute from userspace
+ * to see if it supports poll (Nether 'poll' or 'select' return
+ * an appropriate error code).  When in doubt, set a suitable timeout value.
+ */
+static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
+{
+       struct sysfs_buffer * buffer = filp->private_data;
+       struct kobject * kobj = to_kobj(filp->f_dentry->d_parent);
+       struct sysfs_dirent * sd = filp->f_dentry->d_fsdata;
+       int res = 0;
+
+       poll_wait(filp, &kobj->poll, wait);
+
+       if (buffer->event != atomic_read(&sd->s_event)) {
+               res = POLLERR|POLLPRI;
+               buffer->needs_read_fill = 1;
+       }
+
+       return res;
+}
+
+
+static struct dentry *step_down(struct dentry *dir, const char * name)
+{
+       struct dentry * de;
+
+       if (dir == NULL || dir->d_inode == NULL)
+               return NULL;
+
+       mutex_lock(&dir->d_inode->i_mutex);
+       de = lookup_one_len(name, dir, strlen(name));
+       mutex_unlock(&dir->d_inode->i_mutex);
+       dput(dir);
+       if (IS_ERR(de))
+               return NULL;
+       if (de->d_inode == NULL) {
+               dput(de);
+               return NULL;
+       }
+       return de;
+}
+
+void sysfs_notify(struct kobject * k, char *dir, char *attr)
+{
+       struct dentry *de = k->dentry;
+       if (de)
+               dget(de);
+       if (de && dir)
+               de = step_down(de, dir);
+       if (de && attr)
+               de = step_down(de, attr);
+       if (de) {
+               struct sysfs_dirent * sd = de->d_fsdata;
+               if (sd)
+                       atomic_inc(&sd->s_event);
+               wake_up_interruptible(&k->poll);
+               dput(de);
+       }
+}
+EXPORT_SYMBOL_GPL(sysfs_notify);
+
 const struct file_operations sysfs_file_operations = {
        .read           = sysfs_read_file,
        .write          = sysfs_write_file,
        .llseek         = generic_file_llseek,
        .open           = sysfs_open_file,
        .release        = sysfs_release,
+       .poll           = sysfs_poll,
 };
 
 
@@ -407,17 +486,12 @@ int sysfs_update_file(struct kobject * kobj, const struct attribute * attr)
                    (victim->d_parent->d_inode == dir->d_inode)) {
                        victim->d_inode->i_mtime = CURRENT_TIME;
                        fsnotify_modify(victim);
-
-                       /**
-                        * Drop reference from initial sysfs_get_dentry().
-                        */
-                       dput(victim);
                        res = 0;
                } else
                        d_drop(victim);
                
                /**
-                * Drop the reference acquired from sysfs_get_dentry() above.
+                * Drop the reference acquired from lookup_one_len() above.
                 */
                dput(victim);
        }