Linus Torvalds [off-list ref] writes:

More people *should* generally ask themselves: "was the warning worth it?" 
and then, if the answer is "no", they shouldn't add code, they should 
remove the thing that causes the warning in the first place.

Sure. If a routine uses must_check yet its return value may be
safely ignored then that must_check is simply misplaced and should
be removed. It does not mean all must_checks are bad - each of them
isn't bad unless one can demonstrate it is.

Back to sysfs_create_bin_file() - if one can demonstrate a caller
can safely ignore the return value (which, it seems, is the
case), then exactly this very must_check should be removed.
-- 
Krzysztof Halasa