4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mark Brown <broonie@xxxxxxxxxx> [ 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@xxxxxxxxxx Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> Reviewed-by: Xu Yilun <yilun.xu@xxxxxxxxx> Link: https://lore.kernel.org/r/20230712-regmap-max-transfer-v1-2-80e2aed22e83@xxxxxxxxxx Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/base/regmap/regmap-i2c.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/base/regmap/regmap-i2c.c +++ b/drivers/base/regmap/regmap-i2c.c @@ -246,8 +246,8 @@ static int regmap_i2c_smbus_i2c_read(voi 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,
