• Pontus Andersson's avatar
    i2c: ismt: Separate I2C block read from SMBus block read · c6ebcedb
    Pontus Andersson authored
    Commit b6c159a9 ("i2c: ismt: Don't duplicate the receive length for
    block reads") broke I2C block reads. It aimed to fix normal SMBus block
    read, but changed the correct behavior of I2C block read in the process.
    
    According to Documentation/i2c/smbus-protocol, one vital difference
    between normal SMBus block read and I2C block read is that there is no
    byte count prefixed in the data sent on the wire:
    
     SMBus Block Read:  i2c_smbus_read_block_data()
     S Addr Wr [A] Comm [A]
                S Addr Rd [A] [Count] A [Data] A [Data] A ... A [Data] NA P
    
     I2C Block Read:  i2c_smbus_read_i2c_block_data()
     S Addr Wr [A] Comm [A]
                S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P
    
    Therefore the two transaction types need to be processed differently in
    the driver by copying of the dma_buffer as done previously for the
    I2C_SMBUS_I2C_BLOCK_DATA case.
    
    Fixes: b6c159a9 ("i2c: ismt: Don't duplicate the receive length for block reads")
    Signed-off-by: default avatarPontus Andersson <epontan@gmail.com>
    Tested-by: default avatarStephen Douthit <stephend@adiengineering.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
    c6ebcedb
i2c-ismt.c 26.9 KB