From f9afb326b7bad6ca06eeba9912bd6fb6716a7d92 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Wed, 12 Jul 2023 12:16:40 +0100 Subject: [PATCH] regmap: Account for register length in SMBus I/O limits [ Upstream commit 0c9d2eb5e94792fe64019008a04d4df5e57625af ] The SMBus I2C buses have limits on the size of transfers they can do but do not factor in the register length meaning we may try to do a transfer longer than our length limit, the core will not take care of this. Future changes will factor this out into the core but there are a number of users that assume current behaviour so let's just do something conservative here. This does not take account padding bits but practically speaking these are very rarely if ever used on I2C buses given that they generally run slowly enough to mean there's no issue. Cc: stable@kernel.org Signed-off-by: Mark Brown Reviewed-by: Xu Yilun Link: https://lore.kernel.org/r/20230712-regmap-max-transfer-v1-2-80e2aed22e83@kernel.org Signed-off-by: Mark Brown Signed-off-by: Sasha Levin --- drivers/base/regmap/regmap-i2c.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/base/regmap/regmap-i2c.c b/drivers/base/regmap/regmap-i2c.c index ac9b31c57967..6d934c35a770 100644 --- a/drivers/base/regmap/regmap-i2c.c +++ b/drivers/base/regmap/regmap-i2c.c @@ -242,8 +242,8 @@ static int regmap_i2c_smbus_i2c_read(void *context, const void *reg, static struct regmap_bus regmap_i2c_smbus_i2c_block = { .write = regmap_i2c_smbus_i2c_write, .read = regmap_i2c_smbus_i2c_read, - .max_raw_read = I2C_SMBUS_BLOCK_MAX, - .max_raw_write = I2C_SMBUS_BLOCK_MAX, + .max_raw_read = I2C_SMBUS_BLOCK_MAX - 1, + .max_raw_write = I2C_SMBUS_BLOCK_MAX - 1, }; static const struct regmap_bus *regmap_get_i2c_bus(struct i2c_client *i2c,