From: Andy Shevchenko Date: Tue, 20 Apr 2021 16:44:25 +0000 (+0300) Subject: spi: Avoid undefined behaviour when counting unused native CSs X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f60d7270c8a3d2beb1c23ae0da42497afa3584c2;p=linux.git 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: 7d93aecdb58d ("spi: Add generic support for unused native cs with cs-gpios") Signed-off-by: Andy Shevchenko Link: https://lore.kernel.org/r/20210420164425.40287-2-andriy.shevchenko@linux.intel.com Signed-off-by: Mark Brown --- diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 2e5dca20c8d00..6fe2a9509675f 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -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) {