Commit bebf29b1 authored by Thomas Weißschuh's avatar Thomas Weißschuh Committed by Greg Kroah-Hartman
Browse files

sysfs: introduce callback attribute_group::bin_size 



Several drivers need to dynamically calculate the size of an binary
attribute. Currently this is done by assigning attr->size from the
is_bin_visible() callback.

This has drawbacks:
* It is not documented.
* A single attribute can be instantiated multiple times, overwriting the
  shared size field.
* It prevents the structure to be moved to read-only memory.

Introduce a new dedicated callback to calculate the size of the
attribute.

Signed-off-by: default avatarThomas Weißschuh <linux@weissschuh.net>
Acked-by: default avatarKrzysztof Wilczyński <kw@linux.com>
Link: https://lore.kernel.org/r/20241103-sysfs-const-bin_attr-v2-2-71110628844c@weissschuh.net


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 0afcee13

fs/sysfs/group.c

+2 −0
Original line number Diff line number Diff line
@@ -98,6 +98,8 @@ static int create_files(struct kernfs_node *parent, struct kobject *kobj, 
				if (!mode)

					continue;

			}

			if (grp->bin_size)

				size = grp->bin_size(kobj, *bin_attr, i);



			WARN(mode & ~(SYSFS_PREALLOC | 0664),

			     "Attribute %s: Invalid permissions 0%o\n",

include/linux/sysfs.h

+8 −0
Original line number Diff line number Diff line
@@ -87,6 +87,11 @@ do { \ 
 *		SYSFS_GROUP_VISIBLE() when assigning this callback to

 *		specify separate _group_visible() and _attr_visible()

 *		handlers.

 * @bin_size:

 *		Optional: Function to return the size of a binary attribute

 *		of the group. Will be called repeatedly for each binary

 *		attribute in the group. Overwrites the size field embedded

 *		inside the attribute itself.

 * @attrs:	Pointer to NULL terminated list of attributes.

 * @bin_attrs:	Pointer to NULL terminated list of binary attributes.

 *		Either attrs or bin_attrs or both must be provided.
@@ -97,6 +102,9 @@ struct attribute_group { 
					      struct attribute *, int);

	umode_t			(*is_bin_visible)(struct kobject *,

						  struct bin_attribute *, int);

	size_t			(*bin_size)(struct kobject *,

					    const struct bin_attribute *,

					    int);

	struct attribute	**attrs;

	struct bin_attribute	**bin_attrs;

};