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Commit f8a1af6b authored by Mike Murphy's avatar Mike Murphy Committed by Linus Torvalds
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PATCH [2/2] Documentation/filesystems/sysfs.txt: fix descriptions of device attributes 



Fix descriptions of device attributes to be consistent with the actual
implementations in include/linux/device.h

Signed-off-by: Mike Murphy <mamurph[at]cs.clemson.edu>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 245127db

Documentation/filesystems/sysfs.txt

+28 −22
Original line number Diff line number Diff line
@@ -2,8 +2,10 @@ 
sysfs - _The_ filesystem for exporting kernel objects. 



Patrick Mochel	<mochel@osdl.org>

Mike Murphy <mamurph@cs.clemson.edu>



10 January 2003

Revised:    22 February 2009

Original:   10 January 2003





What it is:
@@ -64,12 +66,13 @@ An attribute definition is simply: 


struct attribute {

        char                    * name;

        struct module		*owner;

        mode_t                  mode;

};





int sysfs_create_file(struct kobject * kobj, struct attribute * attr);

void sysfs_remove_file(struct kobject * kobj, struct attribute * attr);

int sysfs_create_file(struct kobject * kobj, const struct attribute * attr);

void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr);





A bare attribute contains no means to read or write the value of the
@@ -81,8 +84,10 @@ For example, the driver model defines struct device_attribute like: 


struct device_attribute {

	struct attribute	attr;

        ssize_t (*show)(struct device * dev, char * buf);

        ssize_t (*store)(struct device * dev, const char * buf);

	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);

};



int device_create_file(struct device *, struct device_attribute *);
@@ -91,11 +96,7 @@ void device_remove_file(struct device *, struct device_attribute *); 
It also defines this helper for defining device attributes: 



#define DEVICE_ATTR(_name, _mode, _show, _store) \

struct device_attribute dev_attr_##_name = {            \

        .attr = {.name  = __stringify(_name) , .mode   = _mode },      \

        .show   = _show,                                \

        .store  = _store,                               \

};

struct device_attribute dev_attr_##_name = __ATTR(_name, _mode, _show, _store)



For example, declaring
@@ -107,9 +108,9 @@ static struct device_attribute dev_attr_foo = { 
       .attr	= {

		.name = "foo",

		.mode = S_IWUSR | S_IRUGO,

	},

		.show = show_foo,

		.store = store_foo,

	},

};
@@ -161,10 +162,12 @@ To read or write attributes, show() or store() methods must be 
specified when declaring the attribute. The method types should be as

simple as those defined for device attributes:



        ssize_t (*show)(struct device * dev, char * buf);

        ssize_t (*store)(struct device * dev, const char * buf);

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);



IOW, they should take only an object and a buffer as parameters. 

IOW, they should take only an object, an attribute, and a buffer as parameters.





sysfs allocates a buffer of size (PAGE_SIZE) and passes it to the
@@ -300,13 +303,15 @@ Structure: 


struct device_attribute {

	struct attribute	attr;

        ssize_t (*show)(struct device * dev, char * buf);

        ssize_t (*store)(struct device * dev, const char * buf);

	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);

};



Declaring:



DEVICE_ATTR(_name, _str, _mode, _show, _store);

DEVICE_ATTR(_name, _mode, _show, _store);



Creation/Removal:
@@ -342,7 +347,8 @@ Structure: 
struct driver_attribute {

        struct attribute        attr;

        ssize_t (*show)(struct device_driver *, char * buf);

        ssize_t (*store)(struct device_driver *, const char * buf);

        ssize_t (*store)(struct device_driver *, const char * buf,

                         size_t count);

};



Declaring: