There are a few different corner cases to the current logic that seem
undesirable:
* mtd_lock() with offs==0 trips a bounds issue on
ofs - mtd->erasesize < 0
* mtd_unlock() on the middle of a flash that is already unlocked will
return -EINVAL
* probably other corner cases
So, let's stop doing "smart" checks like "check the block below us",
let's just do the following:
(a) pass only non-negative offsets/lengths to stm_is_locked_sr()
(b) add a similar stm_is_unlocked_sr() function, so we can check if the
*entire* range is unlocked (and not just whether some part of it is
unlocked)
Then armed with (b), we can make lock() and unlock() much more
symmetric:
(c) short-circuit the procedure if there is no work to be done, and
(d) check the entire range above/below
This also aligns well with the structure needed for proper TB
(Top/Bottom) support.
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
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