| From a97c2a412056b9110611a9dac1f1af1472212488 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Tue, 20 Apr 2021 19:44:25 +0300 |
| Subject: spi: Avoid undefined behaviour when counting unused native CSs |
| |
| From: Andy Shevchenko <andriy.shevchenko@linux.intel.com> |
| |
| [ Upstream commit f60d7270c8a3d2beb1c23ae0da42497afa3584c2 ] |
| |
| 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 <andriy.shevchenko@linux.intel.com> |
| Link: https://lore.kernel.org/r/20210420164425.40287-2-andriy.shevchenko@linux.intel.com |
| Signed-off-by: Mark Brown <broonie@kernel.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| drivers/spi/spi.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c |
| index a1a85f0baf7c..8c261eac2cee 100644 |
| --- a/drivers/spi/spi.c |
| +++ b/drivers/spi/spi.c |
| @@ -2614,7 +2614,7 @@ 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) { |
| -- |
| 2.30.2 |
| |
