sysfs.txt: add note on available attribute macros

[sfrench/cifs-2.6.git] / Documentation / filesystems / sysfs.txt

diff --git a/Documentation/filesystems/sysfs.txt b/Documentation/filesystems/sysfs.txt
index a1426cabcef12c814ed3527e0d8663eddea8277b..d70c8f112662340e57e01988c266364b8049ad60 100644 (file)
--- a/Documentation/filesystems/sysfs.txt
+++ b/Documentation/filesystems/sysfs.txt
@@ -116,6 +116,27 @@ static struct device_attribute dev_attr_foo = {
        .store = store_foo,
 };
 
+Note as stated in include/linux/kernel.h "OTHER_WRITABLE?  Generally
+considered a bad idea." so trying to set a sysfs file writable for
+everyone will fail reverting to RO mode for "Others".
+
+For the common cases sysfs.h provides convenience macros to make
+defining attributes easier as well as making code more concise and
+readable. The above case could be shortened to:
+
+static struct device_attribute dev_attr_foo = __ATTR_RW(foo);
+
+the list of helpers available to define your wrapper function is:
+__ATTR_RO(name): assumes default name_show and mode 0444
+__ATTR_WO(name): assumes a name_store only and is restricted to mode
+                 0200 that is root write access only.
+__ATTR_RO_MODE(name, mode): fore more restrictive RO access currently
+                 only use case is the EFI System Resource Table
+                 (see drivers/firmware/efi/esrt.c)
+__ATTR_RW(name): assumes default name_show, name_store and setting
+                 mode to 0644.
+__ATTR_NULL: which sets the name to NULL and is used as end of list
+                 indicator (see: kernel/workqueue.c)
 
 Subsystem-Specific Callbacks
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~