6.6-stable review patch. If anyone has any objections, please let me know.
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From: Andy Shevchenko andy.shevchenko@gmail.com
[ Upstream commit d4ea1d504d2701ba04412f98dc00d45a104c52ab ]
If we ever meet a hardware that uses weird register bits and padding, we may end up in off-by-one error since x/8 + y/8 might not be equal to (x + y)/8 in some cases.
bits pad x/8+y/8 (x+y)/8 4..7 0..3 0 0 // x + y from 4 up to 7 4..7 4..7 0 1 // x + y from 8 up to 11 4..7 8..11 1 1 // x + y from 12 up to 15 8..15 0..7 1 1 // x + y from 8 up to 15 8..15 8..15 2 2 // x + y from 16 up to 23
Fix this by using (x+y)/8.
Signed-off-by: Andy Shevchenko andy.shevchenko@gmail.com Link: https://msgid.link/r/20240605205315.19132-1-andy.shevchenko@gmail.com Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/base/regmap/regmap-spi.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/base/regmap/regmap-spi.c b/drivers/base/regmap/regmap-spi.c index 37ab23a9d034..7f14c5ed1e22 100644 --- a/drivers/base/regmap/regmap-spi.c +++ b/drivers/base/regmap/regmap-spi.c @@ -122,8 +122,7 @@ static const struct regmap_bus *regmap_get_spi_bus(struct spi_device *spi, return ERR_PTR(-ENOMEM);
max_msg_size = spi_max_message_size(spi); - reg_reserve_size = config->reg_bits / BITS_PER_BYTE - + config->pad_bits / BITS_PER_BYTE; + reg_reserve_size = (config->reg_bits + config->pad_bits) / BITS_PER_BYTE; if (max_size + reg_reserve_size > max_msg_size) max_size -= reg_reserve_size;