Commit 3b35f2a6 authored by Yury Norov's avatar Yury Norov Committed by Greg Kroah-Hartman
Browse files

bitmap: extend comment to bitmap_print_bitmask/list_to_buf 



Extend comment to new function to warn potential users about caveats.

Signed-off-by: default avatarYury Norov <yury.norov@gmail.com>
Signed-off-by: default avatarBarry Song <song.bao.hua@hisilicon.com>
Link: https://lore.kernel.org/r/20210806110251.560-6-song.bao.hua@hisilicon.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 75bd50fa

lib/bitmap.c

+18 −0
Original line number Diff line number Diff line
@@ -568,6 +568,24 @@ static int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp, 
 * and it can break the size limit of converted decimal list and hexadecimal

 * bitmask.

 *

 * WARNING!

 *

 * This function is not a replacement for sprintf() or bitmap_print_to_pagebuf().

 * It is intended to workaround sysfs limitations discussed above and should be

 * used carefully in general case for the following reasons:

 *  - Time complexity is O(nbits^2/count), comparing to O(nbits) for snprintf().

 *  - Memory complexity is O(nbits), comparing to O(1) for snprintf().

 *  - @off and @count are NOT offset and number of bits to print.

 *  - If printing part of bitmap as list, the resulting string is not a correct

 *    list representation of bitmap. Particularly, some bits within or out of

 *    related interval may be erroneously set or unset. The format of the string

 *    may be broken, so bitmap_parselist-like parser may fail parsing it.

 *  - If printing the whole bitmap as list by parts, user must ensure the order

 *    of calls of the function such that the offset is incremented linearly.

 *  - If printing the whole bitmap as list by parts, user must keep bitmap

 *    unchanged between the very first and very last call. Otherwise concatenated

 *    result may be incorrect, and format may be broken.

 *

 * Returns the number of characters actually printed to @buf

 */

int bitmap_print_bitmask_to_buf(char *buf, const unsigned long *maskp,