[PATCH v1 1/1] spi: Switch to signed types for *_native_cs SPI controller fields

[PATCH v1 1/1] spi: Switch to signed types for *_native_cs SPI controller fields

[Andy Shevchenko]

While fixing undefined behaviour the commit f60d7270c8a3 ("spi: Avoid
undefined behaviour when counting unused native CSs") missed the case
when all CSs are GPIOs and thus unused_native_cs will be evaluated to
-1 in unsigned representation. This will falsely trigger a condition
in the spi_get_gpio_descs().

Switch to signed types for *_native_cs SPI controller fields to fix above.

Fixes: f60d7270c8a3 ("spi: Avoid undefined behaviour when counting unused native CSs")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 include/linux/spi/spi.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 360a3bc767ca..74239d65c7fd 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -644,8 +644,8 @@ struct spi_controller {
 	int			*cs_gpios;
 	struct gpio_desc	**cs_gpiods;
 	bool			use_gpio_descriptors;
-	u8			unused_native_cs;
-	u8			max_native_cs;
+	s8			unused_native_cs;
+	s8			max_native_cs;
 
 	/* statistics */
 	struct spi_statistics	statistics;
-- 
2.30.2

Re: [PATCH v1 1/1] spi: Switch to signed types for *_native_cs SPI controller fields

[Mark Brown]

On Mon, 10 May 2021 16:12:42 +0300, Andy Shevchenko wrote:
> While fixing undefined behaviour the commit f60d7270c8a3 ("spi: Avoid
> undefined behaviour when counting unused native CSs") missed the case
> when all CSs are GPIOs and thus unused_native_cs will be evaluated to
> -1 in unsigned representation. This will falsely trigger a condition
> in the spi_get_gpio_descs().
> 
> Switch to signed types for *_native_cs SPI controller fields to fix above.

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: Switch to signed types for *_native_cs SPI controller fields
      commit: 35f3f8504c3b60a1ae5576e178b27fc0ddd6157d

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark