Driver Attributes
~~~~~~~~~~~~~~~~~
struct driver_attribute {
struct attribute attr;
ssize_t (*show)(struct device_driver *driver, char *buf);
ssize_t (*store)(struct device_driver *, const char * buf, size_t count);
};
Device drivers can export attributes via their sysfs directories.
Drivers can declare attributes using a DRIVER_ATTR macro that works
identically to the DEVICE_ATTR macro.
Example:
DRIVER_ATTR(debug,0644,show_debug,store_debug);
This is equivalent to declaring:
struct driver_attribute driver_attr_debug;
This can then be used to add and remove the attribute from the
driver's directory using:
int driver_create_file(struct device_driver *, const struct driver_attribute *);
void driver_remove_file(struct device_driver *, const struct driver_attribute *);
Device Attributes
~~~~~~~~~~~~~~~~~
struct device_attribute {
struct attribute attr;
ssize_t (*show)(struct device *dev, struct device_attribute *attr,
char *buf);
ssize_t (*store)(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count);
};
Attributes of devices can be exported via drivers using a simple
procfs-like interface.
Please see Documentation/filesystems/sysfs.txt for more information
on how sysfs works.
Attributes are declared using a macro called DEVICE_ATTR:
#define DEVICE_ATTR(name,mode,show,store)
Example:
DEVICE_ATTR(power,0644,show_power,store_power);
This declares a structure of type struct device_attribute named
'dev_attr_power'. This can then be added and removed to the device's
directory using:
int device_create_file(struct device *device, struct device_attribute * entry);
void device_remove_file(struct device * dev, struct device_attribute * attr);
Example:
device_create_file(dev,&dev_attr_power);
device_remove_file(dev,&dev_attr_power);
The file name will be 'power' with a mode of 0644 (-rw-r--r--).