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regmap: Account for register length in SMBus I/O limits

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[ 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 <broonie@kernel.org>
Reviewed-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20230712-regmap-max-transfer-v1-2-80e2aed22e83@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Mark Brown 2023-07-12 12:16:40 +01:00 committed by Greg Kroah-Hartman
parent 7e1d1456c8
commit f9afb326b7
1 changed files with 2 additions and 2 deletions
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4
drivers/base/regmap/regmap-i2c.c
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@ -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,