There are cases when it is useful to check a bit-mask has only one bit set. Add a generic helper for it instead of baking own one for each user. Signed-off-by: Matti Vaittinen --- I am not at all sure what would be the best place for this. Please let me know if you think some other file would be more appropriate. --- include/linux/bitops.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 5e62e2383b7f..dd6c7baed3d3 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -66,6 +66,26 @@ extern unsigned long __sw_hweight64(__u64 w); (start) < (size); \ (start) = find_next_clump8(&(clump), (bits), (size), (start) + 8)) +/** + * single_bit_set - check if only one bit is set in value + * @bits: value to check + * @bits_to_check: how many bits we should scan + * + * Return: true if only one of the checked bits is set, othervice return false. + */ +static inline bool single_bit_set(const unsigned long bits, int bits_to_check) +{ + int bit; + + bit = find_first_bit(&bits, bits_to_check); + if (bit == bits_to_check) + return false; + + bit = find_next_bit(&bits, bits_to_check, bit + 1); + + return (bit == bits_to_check); +} + static inline int get_bitmask_order(unsigned int count) { int order; -- 2.31.1 -- Matti Vaittinen, Linux device drivers ROHM Semiconductors, Finland SWDC Kiviharjunlenkki 1E 90220 OULU FINLAND ~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~ Simon says - in Latin please. ~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~ Thanks to Simon Glass for the translation =]