From 4dd9572abc224019a042b662fb0eececca283cb9 Mon Sep 17 00:00:00 2001 From: Stephen Warren Date: Thu, 30 May 2013 09:59:39 -0600 Subject: [PATCH] spi: fix undefined behaviour in SPI_BPW_RANGE_MASK The parameters to SPI_BPW_RANGE_MASK() are in the range 1..32. If 32 is used as a parameter, part of the expression is "1 << 32". Since 32 is >= the size of the type in use, such a shift is undefined behaviour. Add macro SPI_BIT_MASK to Implement a special case and thus avoid undefined behaviour. Use this new macro rather than BIT() when implementing SPI_BPW_RANGE_MASK(). This fixes build warnings such as: drivers/spi/spi-gpio.c:446:2: warning: left shift count >= width of type [enabled by default] SPI_BPW_MASK() already avoids this, since its parameter is also in range 1..32, yet it only shifts by up to one less than the input parameter. Reported-by: Fengguang Wu Signed-off-by: Stephen Warren Signed-off-by: Mark Brown --- include/linux/spi/spi.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 173725622252..3e9479134d9d 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -309,7 +309,8 @@ struct spi_master { /* bitmask of supported bits_per_word for transfers */ u32 bits_per_word_mask; #define SPI_BPW_MASK(bits) BIT((bits) - 1) -#define SPI_BPW_RANGE_MASK(min, max) ((BIT(max) - 1) - (BIT(min) - 1)) +#define SPI_BIT_MASK(bits) (((bits) == 32) ? ~0UL : (BIT(bits) - 1)) +#define SPI_BPW_RANGE_MASK(min, max) (SPI_BIT_MASK(max) - SPI_BIT_MASK(min)) /* other constraints relevant to this driver */ u16 flags; -- 2.20.1