Commit effa4531 authored by Heiner Kallweit's avatar Heiner Kallweit Committed by Wolfram Sang
Browse files

i2c: i801: Don't silently correct invalid transfer size 



If an invalid block size is provided, reject it instead of silently
changing it to a supported value. Especially critical I see the case of
a write transfer with block length 0. In this case we have no guarantee
that the byte we would write is valid. When silently reducing a read to
32 bytes then we don't return an error and the caller may falsely
assume that we returned the full requested data.

If this change should break any (broken) caller, then I think we should
fix the caller.

Signed-off-by: default avatarHeiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: default avatarJean Delvare <jdelvare@suse.de>
Signed-off-by: default avatarWolfram Sang <wsa@kernel.org>
parent bd2fdedb

drivers/i2c/busses/i2c-i801.c

+5 −10
Original line number Diff line number Diff line
@@ -775,6 +775,11 @@ static int i801_block_transaction(struct i801_priv *priv, union i2c_smbus_data * 
	int result = 0;

	unsigned char hostc;



	if (read_write == I2C_SMBUS_READ && command == I2C_SMBUS_BLOCK_DATA)

		data->block[0] = I2C_SMBUS_BLOCK_MAX;

	else if (data->block[0] < 1 || data->block[0] > I2C_SMBUS_BLOCK_MAX)

		return -EPROTO;



	if (command == I2C_SMBUS_I2C_BLOCK_DATA) {

		if (read_write == I2C_SMBUS_WRITE) {

			/* set I2C_EN bit in configuration register */
@@ -788,16 +793,6 @@ static int i801_block_transaction(struct i801_priv *priv, union i2c_smbus_data * 
		}

	}



	if (read_write == I2C_SMBUS_WRITE

	 || command == I2C_SMBUS_I2C_BLOCK_DATA) {

		if (data->block[0] < 1)

			data->block[0] = 1;

		if (data->block[0] > I2C_SMBUS_BLOCK_MAX)

			data->block[0] = I2C_SMBUS_BLOCK_MAX;

	} else {

		data->block[0] = 32;	/* max for SMBus block reads */

	}



	/* Experience has shown that the block buffer can only be used for

	   SMBus (not I2C) block transactions, even though the datasheet

	   doesn't mention this limitation. */