Commit 4dd9572a authored May 30, 2013 by Stephen Warren Committed by Mark Brown Jun 01, 2013

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 <fengguang.wu@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark 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;

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