attributes.
Attributes should be ASCII text files, preferably with only one value
-per file. It is noted that it may not be efficient to contain only
+per file. It is noted that it may not be efficient to contain only one
value per file, so it is socially acceptable to express an array of
values of the same type.
It also defines this helper for defining device attributes:
-#define DEVICE_ATTR(_name,_mode,_show,_store) \
+#define DEVICE_ATTR(_name, _mode, _show, _store) \
struct device_attribute dev_attr_##_name = { \
.attr = {.name = __stringify(_name) , .mode = _mode }, \
.show = _show, \
For example, declaring
-static DEVICE_ATTR(foo,0644,show_foo,store_foo);
+static DEVICE_ATTR(foo, S_IWUSR | S_IRUGO, show_foo, store_foo);
is equivalent to doing:
static struct device_attribute dev_attr_foo = {
.attr = {
.name = "foo",
- .mode = 0644,
+ .mode = S_IWUSR | S_IRUGO,
},
.show = show_foo,
.store = store_foo,
show and store methods of the attribute owners.
struct sysfs_ops {
- ssize_t (*show)(struct kobject *, struct attribute *,char *);
- ssize_t (*store)(struct kobject *,struct attribute *,const char *);
+ ssize_t (*show)(struct kobject *, struct attribute *, char *);
+ ssize_t (*store)(struct kobject *, struct attribute *, const char *);
};
[ Subsystems should have already defined a struct kobj_type as a
To illustrate:
-#define to_dev_attr(_attr) container_of(_attr,struct device_attribute,attr)
+#define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)
#define to_dev(d) container_of(d, struct device, kobj)
static ssize_t
ssize_t ret = 0;
if (dev_attr->show)
- ret = dev_attr->show(dev,buf);
+ ret = dev_attr->show(dev, buf);
return ret;
}
static ssize_t show_name(struct device *dev, struct device_attribute *attr, char *buf)
{
- return sprintf(buf,"%s\n",dev->name);
+ return snprintf(buf, PAGE_SIZE, "%s\n", dev->name);
}
static ssize_t store_name(struct device * dev, const char * buf)
{
- sscanf(buf,"%20s",dev->name);
- return strlen(buf);
+ sscanf(buf, "%20s", dev->name);
+ return strnlen(buf, PAGE_SIZE);
}
-static DEVICE_ATTR(name,S_IRUGO,show_name,store_name);
+static DEVICE_ATTR(name, S_IRUGO, show_name, store_name);
(Note that the real implementation doesn't allow userspace to set the
The sysfs directory arrangement exposes the relationship of kernel
data structures.
-The top level sysfs diretory looks like:
+The top level sysfs directory looks like:
block/
bus/
devices/
firmware/
net/
+fs/
devices/ contains a filesystem representation of the device tree. It maps
directly to the internal kernel device tree, which is a hierarchy of
for devices on that particular bus (this assumes that drivers do not
span multiple bus types).
+fs/ contains a directory for some filesystems. Currently each
+filesystem wanting to export attributes must create its own hierarchy
+below fs/ (see ./fuse.txt for an example).
+
More information can driver-model specific features can be found in
Documentation/driver-model/.
Declaring:
-DEVICE_ATTR(_name,_str,_mode,_show,_store);
+DEVICE_ATTR(_name, _str, _mode, _show, _store);
Creation/Removal:
Declaring:
-BUS_ATTR(_name,_mode,_show,_store)
+BUS_ATTR(_name, _mode, _show, _store)
Creation/Removal:
Declaring:
-DRIVER_ATTR(_name,_mode,_show,_store)
+DRIVER_ATTR(_name, _mode, _show, _store)
Creation/Removal: