The migration of 'struct attribute' and its related structures and
macros are more complicated than those for 'struct bin_attribute'.
Mostly because they are all shared by various custom attribute types.
Introduce some initial utilities to support the migration.
These are enough to migrate some specialized attributes atomically or
those which don't use 'struct attribute' in their callbacks stepwise.

The big outstanding problems are 'struct device_attribute' and
'struct kobj_attribute'. These are used everywhere and I'm not yet sure
about a migration plan.

Based on driver-core-next.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
Changes in v2:
- Rebase onto driver-core-next
- Simplify attribute macro definitions
- +Cc Danilo
- Link to v1: https://lore.kernel.org/r/20250116-sysfs-const-attr-prep-v1-0-15e72dba4205@weissschuh.net

---
Thomas Weißschuh (7):
      sysfs: attribute_group: allow registration of const attribute
      sysfs: transparently handle const pointers in ATTRIBUTE_GROUPS()
      sysfs: introduce __SYSFS_FUNCTION_ALTERNATIVE()
      sysfs: attribute_group: enable const variants of is_visible()
      samples/kobject: add is_visible() callback to attribute group
      samples/kobject: constify 'struct foo_attribute'
      sysfs: simplify attribute definition macros

 fs/sysfs/group.c               | 10 +++++++--
 include/linux/sysfs.h          | 48 +++++++++++++++++++++++++-----------------
 samples/kobject/kset-example.c | 44 ++++++++++++++++++++++++++------------
 3 files changed, 67 insertions(+), 35 deletions(-)
---
base-commit: c79cbde9b7bc7a650af96269588518950e3c2441
change-id: 20250114-sysfs-const-attr-prep-e9414982dc4f

Best regards,
-- 
Thomas Weißschuh <linux@weissschuh.net>