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Commit 4dd9572a authored by Stephen Warren's avatar Stephen Warren Committed by Mark Brown
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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: default avatarFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: default avatarStephen Warren <swarren@nvidia.com>
Signed-off-by: default avatarMark Brown <broonie@linaro.org>
parent 6051426f

include/linux/spi/spi.h

+2 −1
Original line number Diff line number Diff line
@@ -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;