3 files changed, 175 insertions, 38 deletions

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 548556ff2506..efc97d9b7860 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -45,44 +45,15 @@ struct file_operations debugfs_file_operations = {
         .open =         default_open,
 };
 
-#define simple_type(type, format, temptype, strtolfn)                           \
-static ssize_t read_file_##type(struct file *file, char __user *user_buf,       \
-                                size_t count, loff_t *ppos)                     \
-{                                                                               \
-        char buf[32];                                                           \
-        type *val = file->private_data;                                         \
-                                                                                \
-        snprintf(buf, sizeof(buf), format "\n", *val);                          \
-        return simple_read_from_buffer(user_buf, count, ppos, buf, strlen(buf));\
-}                                                                               \
-static ssize_t write_file_##type(struct file *file, const char __user *user_buf,\
-                                 size_t count, loff_t *ppos)                    \
-{                                                                               \
-        char *endp;                                                             \
-        char buf[32];                                                           \
-        int buf_size;                                                           \
-        type *val = file->private_data;                                         \
-        temptype tmp;                                                           \
-                                                                                \
-        memset(buf, 0x00, sizeof(buf));                                         \
-        buf_size = min(count, (sizeof(buf)-1));                                 \
-        if (copy_from_user(buf, user_buf, buf_size))                            \
-                return -EFAULT;                                                 \
-                                                                                \
-        tmp = strtolfn(buf, &endp, 0);                                          \
-        if ((endp == buf) || ((type)tmp != tmp))                                \
-                return -EINVAL;                                                 \
-        *val = tmp;                                                             \
-        return count;                                                           \
-}                                                                               \
-static struct file_operations fops_##type = {                                   \
-        .read =         read_file_##type,                                       \
-        .write =        write_file_##type,                                      \
-        .open =         default_open,                                           \
-};
-simple_type(u8, "%c", unsigned long, simple_strtoul);
-simple_type(u16, "%hi", unsigned long, simple_strtoul);
-simple_type(u32, "%i", unsigned long, simple_strtoul);
+static void debugfs_u8_set(void *data, u64 val)
+{
+        *(u8 *)data = val;
+}
+static u64 debugfs_u8_get(void *data)
+{
+        return *(u8 *)data;
+}
+DEFINE_SIMPLE_ATTRIBUTE(fops_u8, debugfs_u8_get, debugfs_u8_set, "%llu\n");
 
 /**
  * debugfs_create_u8 - create a file in the debugfs filesystem that is used to read and write a unsigned 8 bit value.
@@ -116,6 +87,16 @@ struct dentry *debugfs_create_u8(const char *name, mode_t mode,
 }
 EXPORT_SYMBOL_GPL(debugfs_create_u8);
 
+static void debugfs_u16_set(void *data, u64 val)
+{
+        *(u16 *)data = val;
+}
+static u64 debugfs_u16_get(void *data)
+{
+        return *(u16 *)data;
+}
+DEFINE_SIMPLE_ATTRIBUTE(fops_u16, debugfs_u16_get, debugfs_u16_set, "%llu\n");
+
 /**
  * debugfs_create_u16 - create a file in the debugfs filesystem that is used to read and write a unsigned 8 bit value.
  *
@@ -148,6 +129,16 @@ struct dentry *debugfs_create_u16(const char *name, mode_t mode,
 }
 EXPORT_SYMBOL_GPL(debugfs_create_u16);
 
+static void debugfs_u32_set(void *data, u64 val)
+{
+        *(u32 *)data = val;
+}
+static u64 debugfs_u32_get(void *data)
+{
+        return *(u32 *)data;
+}
+DEFINE_SIMPLE_ATTRIBUTE(fops_u32, debugfs_u32_get, debugfs_u32_set, "%llu\n");
+
 /**
  * debugfs_create_u32 - create a file in the debugfs filesystem that is used to read and write a unsigned 8 bit value.
  *
diff --git a/fs/libfs.c b/fs/libfs.c
index f90b29595927..5025563e7379 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -519,6 +519,102 @@ int simple_transaction_release(struct inode *inode, struct file *file)
         return 0;
 }
 
+/* Simple attribute files */
+
+struct simple_attr {
+        u64 (*get)(void *);
+        void (*set)(void *, u64);
+        char get_buf[24];       /* enough to store a u64 and "\n\0" */
+        char set_buf[24];
+        void *data;
+        const char *fmt;        /* format for read operation */
+        struct semaphore sem;   /* protects access to these buffers */
+};
+
+/* simple_attr_open is called by an actual attribute open file operation
+ * to set the attribute specific access operations. */
+int simple_attr_open(struct inode *inode, struct file *file,
+                     u64 (*get)(void *), void (*set)(void *, u64),
+                     const char *fmt)
+{
+        struct simple_attr *attr;
+
+        attr = kmalloc(sizeof(*attr), GFP_KERNEL);
+        if (!attr)
+                return -ENOMEM;
+
+        attr->get = get;
+        attr->set = set;
+        attr->data = inode->u.generic_ip;
+        attr->fmt = fmt;
+        init_MUTEX(&attr->sem);
+
+        file->private_data = attr;
+
+        return nonseekable_open(inode, file);
+}
+
+int simple_attr_close(struct inode *inode, struct file *file)
+{
+        kfree(file->private_data);
+        return 0;
+}
+
+/* read from the buffer that is filled with the get function */
+ssize_t simple_attr_read(struct file *file, char __user *buf,
+                         size_t len, loff_t *ppos)
+{
+        struct simple_attr *attr;
+        size_t size;
+        ssize_t ret;
+
+        attr = file->private_data;
+
+        if (!attr->get)
+                return -EACCES;
+
+        down(&attr->sem);
+        if (*ppos) /* continued read */
+                size = strlen(attr->get_buf);
+        else      /* first read */
+                size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
+                                 attr->fmt,
+                                 (unsigned long long)attr->get(attr->data));
+
+        ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
+        up(&attr->sem);
+        return ret;
+}
+
+/* interpret the buffer as a number to call the set function with */
+ssize_t simple_attr_write(struct file *file, const char __user *buf,
+                          size_t len, loff_t *ppos)
+{
+        struct simple_attr *attr;
+        u64 val;
+        size_t size;
+        ssize_t ret;
+
+        attr = file->private_data;
+
+        if (!attr->set)
+                return -EACCES;
+
+        down(&attr->sem);
+        ret = -EFAULT;
+        size = min(sizeof(attr->set_buf) - 1, len);
+        if (copy_from_user(attr->set_buf, buf, size))
+                goto out;
+
+        ret = len; /* claim we got the whole input */
+        attr->set_buf[size] = '\0';
+        val = simple_strtol(attr->set_buf, NULL, 0);
+        attr->set(attr->data, val);
+out:
+        up(&attr->sem);
+        return ret;
+}
+
 EXPORT_SYMBOL(dcache_dir_close);
 EXPORT_SYMBOL(dcache_dir_lseek);
 EXPORT_SYMBOL(dcache_dir_open);
@@ -547,3 +643,7 @@ EXPORT_SYMBOL(simple_read_from_buffer);
 EXPORT_SYMBOL(simple_transaction_get);
 EXPORT_SYMBOL(simple_transaction_read);
 EXPORT_SYMBOL(simple_transaction_release);
+EXPORT_SYMBOL_GPL(simple_attr_open);
+EXPORT_SYMBOL_GPL(simple_attr_close);
+EXPORT_SYMBOL_GPL(simple_attr_read);
+EXPORT_SYMBOL_GPL(simple_attr_write);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0180102dace1..9b8b696d4f15 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1657,6 +1657,52 @@ static inline void simple_transaction_set(struct file *file, size_t n)
         ar->size = n;
 }
 
+/*
+ * simple attribute files
+ *
+ * These attributes behave similar to those in sysfs:
+ *
+ * Writing to an attribute immediately sets a value, an open file can be
+ * written to multiple times.
+ *
+ * Reading from an attribute creates a buffer from the value that might get
+ * read with multiple read calls. When the attribute has been read
+ * completely, no further read calls are possible until the file is opened
+ * again.
+ *
+ * All attributes contain a text representation of a numeric value
+ * that are accessed with the get() and set() functions.
+ */
+#define DEFINE_SIMPLE_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 struct file_operations __fops = {                                \
+        .owner   = THIS_MODULE,                                         \
+        .open    = __fops ## _open,                                     \
+        .release = simple_attr_close,                                   \
+        .read    = simple_attr_read,                                    \
+        .write   = simple_attr_write,                                   \
+};
+
+static inline void __attribute__((format(printf, 1, 2)))
+__simple_attr_check_format(const char *fmt, ...)
+{
+        /* don't do anything, just let the compiler check the arguments; */
+}
+
+int simple_attr_open(struct inode *inode, struct file *file,
+                     u64 (*get)(void *), void (*set)(void *, u64),
+                     const char *fmt);
+int simple_attr_close(struct inode *inode, struct file *file);
+ssize_t simple_attr_read(struct file *file, char __user *buf,
+                         size_t len, loff_t *ppos);
+ssize_t simple_attr_write(struct file *file, const char __user *buf,
+                          size_t len, loff_t *ppos);
+
+
 #ifdef CONFIG_SECURITY
 static inline char *alloc_secdata(void)
 {