There may be cases (most obviously, sysfs-writable charp parameters) where
a module needs to prevent sysfs access to parameters.
Rather than express this in terms of a big lock, the functions are
expressed in terms of what they protect against. This is clearer, esp.
if the implementation changes to a module-level or even param-level lock.
Signed-off-by: Rusty Russell <firstname.lastname@example.org>
Reviewed-by: Takashi Iwai <email@example.com>
Tested-by: Phil Carmody <firstname.lastname@example.org>