debugfs: add helpers for exporting a size_t simple value

In the same spirit as debugfs_create_*(), introduce helpers for
exporting size_t values over debugfs.

The only trick done is that the format verifier is kept at %llu
instead of %zu; otherwise type warnings would pop up:

format ‘%zu’ expects type ‘size_t’, but argument 2 has type ‘long long unsigned int’

There is no real way to fix this one--however, we can consider %llu
and %zu to be compatible if we consider that we are using the same for
validating in debugfs_create_{x,u}{8,16,32}().

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

fs/debugfs/file.c

@@ -294,6 +294,38 @@ struct dentry *debugfs_create_x32(const char *name, mode_t mode,
 }
 EXPORT_SYMBOL_GPL(debugfs_create_x32);
 
+
+static int debugfs_size_t_set(void *data, u64 val)
+{
+	*(size_t *)data = val;
+	return 0;
+}
+static int debugfs_size_t_get(void *data, u64 *val)
+{
+	*val = *(size_t *)data;
+	return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(fops_size_t, debugfs_size_t_get, debugfs_size_t_set,
+			"%llu\n");	/* %llu and %zu are more or less the same */
+
+/**
+ * debugfs_create_size_t - create a debugfs file that is used to read and write an size_t value
+ * @name: a pointer to a string containing the name of the file to create.
+ * @mode: the permission that the file should have
+ * @parent: a pointer to the parent dentry for this file.  This should be a
+ *          directory dentry if set.  If this parameter is %NULL, then the
+ *          file will be created in the root of the debugfs filesystem.
+ * @value: a pointer to the variable that the file should read to and write
+ *         from.
+ */
+struct dentry *debugfs_create_size_t(const char *name, mode_t mode,
+				     struct dentry *parent, size_t *value)
+{
+	return debugfs_create_file(name, mode, parent, value, &fops_size_t);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_size_t);
+
+
 static ssize_t read_file_bool(struct file *file, char __user *user_buf,
 			      size_t count, loff_t *ppos)
 {

include/linux/debugfs.h

@@ -63,6 +63,8 @@ struct dentry *debugfs_create_x16(const char *name, mode_t mode,
 				  struct dentry *parent, u16 *value);
 struct dentry *debugfs_create_x32(const char *name, mode_t mode,
 				  struct dentry *parent, u32 *value);
+struct dentry *debugfs_create_size_t(const char *name, mode_t mode,
+				     struct dentry *parent, size_t *value);
 struct dentry *debugfs_create_bool(const char *name, mode_t mode,
 				  struct dentry *parent, u32 *value);