Commit 44a47f0e authored by Nicholas Mc Guire's avatar Nicholas Mc Guire Committed by Jonathan Corbet
Browse files

sysfs.txt: add note on available attribute macros 



The common cases of attributes wrappers should probably be using the
__ATTR_XXX macros to make code more concise and readable but the current
sysfs.txt does not point developers to those convenience macros. Further
there is no note in sysfs.txt currently explaining why trying to set a
sysfs file to mode 0666 will fail respectively revert to 0664.

Signed-off-by: default avatarNicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent 8a3680e2

Documentation/filesystems/sysfs.txt

+21 −0
Original line number Diff line number Diff line
@@ -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)



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