On Mon, Oct 02, 2017 at 02:45:19PM +0200, Pontus Andersson wrote:
> Commit b6c159a9cb69 ("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: b6c159a9cb69 ("i2c: ismt: Don't duplicate the receive length for block reads")
> Signed-off-by: Pontus Andersson <epontan@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Applied to for-current, thanks!
Might have been good to CC the patch author of the problematic commit,
too.
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