driverfs: add glue layer for drivers to export attributes via driverfs

This defines struct driver_attribute so device drivers themselves can export attributes 
via driverfs.

The macro DRIVER_ATTR is defined for declaring the attributes.

driver_{create,remove}_file are implemented for creating and removing files.

 

drivers/base/fs/driver.c

 #include <linux/device.h>
+#include <linux/module.h>
+#include <linux/stat.h>
+#include <linux/err.h>
 #include "fs.h"
 
+#define to_drv_attr(_attr) container_of(_attr,struct driver_attribute,attr)
+
+#define to_drv(d) container_of(d, struct device_driver, dir)
+
+
+/* driverfs ops for device attribute files */
+
+static int
+drv_attr_open(struct driver_dir_entry * dir)
+{
+	struct device_driver * drv = to_drv(dir);
+	get_driver(drv);
+	return 0;
+}
+
+static int
+drv_attr_close(struct driver_dir_entry * dir)
+{
+	struct device_driver * drv = to_drv(dir);
+	put_driver(drv);
+	return 0;
+}
+
+static ssize_t
+drv_attr_show(struct driver_dir_entry * dir, struct attribute * attr,
+	      char * buf, size_t count, loff_t off)
+{
+	struct driver_attribute * drv_attr = to_drv_attr(attr);
+	struct device_driver * drv = to_drv(dir);
+	ssize_t ret = 0;
+
+	if (drv_attr->show)
+		ret = drv_attr->show(drv,buf,count,off);
+	return ret;
+}
+
+static ssize_t
+drv_attr_store(struct driver_dir_entry * dir, struct attribute * attr,
+	       const char * buf, size_t count, loff_t off)
+{
+	struct driver_attribute * drv_attr = to_drv_attr(attr);
+	struct device_driver * drv = to_drv(dir);
+	ssize_t ret = 0;
+
+	if (drv_attr->store)
+		ret = drv_attr->store(drv,buf,count,off);
+	return ret;
+}
+
+static struct driverfs_ops drv_attr_ops = {
+	open:	drv_attr_open,
+	close:	drv_attr_close,
+	show:	drv_attr_show,
+	store:	drv_attr_store,
+};
+
+int driver_create_file(struct device_driver * drv, struct driver_attribute * attr)
+{
+	int error;
+	if (get_driver(drv)) {
+		error = driverfs_create_file(&attr->attr,&drv->dir);
+		put_driver(drv);
+	} else
+		error = -EINVAL;
+	return error;
+}
+
+void driver_remove_file(struct device_driver * drv, struct driver_attribute * attr)
+{
+	if (get_driver(drv)) {
+		driverfs_remove_file(&drv->dir,attr->attr.name);
+		put_driver(drv);
+	}
+}
+
 /**
  * driver_make_dir - create a driverfs directory for a driver
  * @drv:	driver in question
@@ -8,6 +86,8 @@
 int driver_make_dir(struct device_driver * drv)
 {
 	drv->dir.name = drv->name;
+	drv->dir.ops = &drv_attr_ops;
+
 	return device_create_dir(&drv->dir,&drv->bus->driver_dir);
 }
 
@@ -16,3 +96,5 @@ void driver_remove_dir(struct device_driver * drv)
 	driverfs_remove_dir(&drv->dir);
 }
 
+EXPORT_SYMBOL(driver_create_file);
+EXPORT_SYMBOL(driver_remove_file);

include/linux/device.h

@@ -142,6 +142,24 @@ extern int driver_for_each_dev(struct device_driver * drv, void * data,
 			       int (*callback)(struct device * dev, void * data));
 
 
+/* driverfs interface for exporting driver attributes */
+
+struct driver_attribute {
+	struct attribute	attr;
+	ssize_t (*show)(struct device_driver *, char * buf, size_t count, loff_t off);
+	ssize_t (*store)(struct device_driver *, const char * buf, size_t count, loff_t off);
+};
+
+#define DRIVER_ATTR(_name,_str,_mode,_show,_store)	\
+struct driver_attribute driver_attr_##_name = { 		\
+	.attr = {.name	= _str,	.mode	= _mode },	\
+	.show	= _show,				\
+	.store	= _store,				\
+};
+
+extern int driver_create_file(struct device_driver *, struct driver_attribute *);
+extern void driver_remove_file(struct device_driver *, struct driver_attribute *);
+
 struct device {
 	struct list_head g_list;        /* node in depth-first order list */
 	struct list_head node;		/* node in sibling list */