sysfs: refill attribute buffer when reading from offset 0

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

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 4045bdcc4b331dbf7f4cdd7c6d781f16021ffbf2..ade9a7e6a75763cd11304a638113f86e18f09d01 100644 (file)
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -12,6 +12,8 @@
 
 #include <linux/module.h>
 #include <linux/kobject.h>
+#include <linux/kallsyms.h>
+#include <linux/slab.h>
 #include <linux/namei.h>
 #include <linux/poll.h>
 #include <linux/list.h>
@@ -20,43 +22,6 @@
 
 #include "sysfs.h"
 
-#define to_sattr(a) container_of(a,struct subsys_attribute, attr)
-
-/*
- * Subsystem file operations.
- * These operations allow subsystems to have files that can be 
- * read/written. 
- */
-static ssize_t 
-subsys_attr_show(struct kobject * kobj, struct attribute * attr, char * page)
-{
-       struct kset *kset = to_kset(kobj);
-       struct subsys_attribute * sattr = to_sattr(attr);
-       ssize_t ret = -EIO;
-
-       if (sattr->show)
-               ret = sattr->show(kset, page);
-       return ret;
-}
-
-static ssize_t 
-subsys_attr_store(struct kobject * kobj, struct attribute * attr, 
-                 const char * page, size_t count)
-{
-       struct kset *kset = to_kset(kobj);
-       struct subsys_attribute * sattr = to_sattr(attr);
-       ssize_t ret = -EIO;
-
-       if (sattr->store)
-               ret = sattr->store(kset, page, count);
-       return ret;
-}
-
-static struct sysfs_ops subsys_sysfs_ops = {
-       .show   = subsys_attr_show,
-       .store  = subsys_attr_store,
-};
-
 /*
  * There's one sysfs_buffer for each open file and one
  * sysfs_open_dirent for each sysfs_dirent with one or more open
@@ -66,7 +31,7 @@ static struct sysfs_ops subsys_sysfs_ops = {
  * sysfs_dirent->s_attr.open points to sysfs_open_dirent.  s_attr.open
  * is protected by sysfs_open_dirent_lock.
  */
-static spinlock_t sysfs_open_dirent_lock = SPIN_LOCK_UNLOCKED;
+static DEFINE_SPINLOCK(sysfs_open_dirent_lock);
 
 struct sysfs_open_dirent {
        atomic_t                refcnt;
@@ -123,7 +88,12 @@ static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer
         * The code works fine with PAGE_SIZE return but it's likely to
         * indicate truncated result or overflow in normal use cases.
         */
-       BUG_ON(count >= (ssize_t)PAGE_SIZE);
+       if (count >= (ssize_t)PAGE_SIZE) {
+               print_symbol("fill_read_buffer: %s returned bad count\n",
+                       (unsigned long)ops->show);
+               /* Try to struggle along */
+               count = PAGE_SIZE - 1;
+       }
        if (count >= 0) {
                buffer->needs_read_fill = 0;
                buffer->count = count;
@@ -159,7 +129,7 @@ sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
        ssize_t retval = 0;
 
        mutex_lock(&buffer->mutex);
-       if (buffer->needs_read_fill) {
+       if (buffer->needs_read_fill || *ppos == 0) {
                retval = fill_read_buffer(file->f_path.dentry,buffer);
                if (retval)
                        goto out;
@@ -354,31 +324,23 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
 {
        struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
        struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
-       struct sysfs_buffer * buffer;
-       struct sysfs_ops * ops = NULL;
-       int error;
+       struct sysfs_buffer *buffer;
+       struct sysfs_ops *ops;
+       int error = -EACCES;
 
        /* need attr_sd for attr and ops, its parent for kobj */
        if (!sysfs_get_active_two(attr_sd))
                return -ENODEV;
 
-       /* if the kobject has no ktype, then we assume that it is a subsystem
-        * itself, and use ops for it.
-        */
-       if (kobj->kset && kobj->kset->ktype)
-               ops = kobj->kset->ktype->sysfs_ops;
-       else if (kobj->ktype)
+       /* every kobject with an attribute needs a ktype assigned */
+       if (kobj->ktype && kobj->ktype->sysfs_ops)
                ops = kobj->ktype->sysfs_ops;
-       else
-               ops = &subsys_sysfs_ops;
-
-       error = -EACCES;
-
-       /* No sysfs operations, either from having no subsystem,
-        * or the subsystem have no operations.
-        */
-       if (!ops)
+       else {
+               printk(KERN_ERR "missing sysfs attribute operations for "
+                      "kobject: %s\n", kobject_name(kobj));
+               WARN_ON(1);
                goto err_out;
+       }
 
        /* File needs write support.
         * The inode's perms must say it's ok, 
@@ -448,8 +410,7 @@ static int sysfs_release(struct inode *inode, struct file *filp)
  * 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'.
+ * need to close and re-open the file, or seek to 0 and read again.
  * 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 (Neither 'poll' nor 'select' return
@@ -568,7 +529,11 @@ int sysfs_add_file_to_group(struct kobject *kobj,
        struct sysfs_dirent *dir_sd;
        int error;
 
-       dir_sd = sysfs_get_dirent(kobj->sd, group);
+       if (group)
+               dir_sd = sysfs_get_dirent(kobj->sd, group);
+       else
+               dir_sd = sysfs_get(kobj->sd);
+
        if (!dir_sd)
                return -ENOENT;
 
@@ -656,7 +621,10 @@ void sysfs_remove_file_from_group(struct kobject *kobj,
 {
        struct sysfs_dirent *dir_sd;
 
-       dir_sd = sysfs_get_dirent(kobj->sd, group);
+       if (group)
+               dir_sd = sysfs_get_dirent(kobj->sd, group);
+       else
+               dir_sd = sysfs_get(kobj->sd);
        if (dir_sd) {
                sysfs_hash_and_remove(dir_sd, attr->name);
                sysfs_put(dir_sd);