Unverified Commit f60d7270 authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Mark Brown
Browse files

spi: Avoid undefined behaviour when counting unused native CSs 



ffz(), that has been used to count unused native CSs,
might cause undefined behaviour when called against ~0U.
To fix that, open code it with ffs(~value) - 1.

Fixes: 7d93aecd ("spi: Add generic support for unused native cs with cs-gpios")
Signed-off-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210420164425.40287-2-andriy.shevchenko@linux.intel.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent dbaca8e5

drivers/spi/spi.c

+1 −1
Original line number Diff line number Diff line
@@ -2611,7 +2611,7 @@ static int spi_get_gpio_descs(struct spi_controller *ctlr) 
		native_cs_mask |= BIT(i);

	}



	ctlr->unused_native_cs = ffz(native_cs_mask);

	ctlr->unused_native_cs = ffs(~native_cs_mask) - 1;



	if ((ctlr->flags & SPI_MASTER_GPIO_SS) && num_cs_gpios &&

	    ctlr->max_native_cs && ctlr->unused_native_cs >= ctlr->max_native_cs) {