From 4d4f527029e290d8e67703409518af9b4a71edb1 Mon Sep 17 00:00:00 2001 From: Pontus Andersson Date: Mon, 2 Oct 2017 14:45:19 +0200 Subject: [PATCH] i2c: ismt: Separate I2C block read from SMBus block read commit c6ebcedbab7ca78984959386012a17b21183e1a3 upstream. 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 Tested-by: Stephen Douthit Signed-off-by: Wolfram Sang Signed-off-by: Greg Kroah-Hartman --- drivers/i2c/busses/i2c-ismt.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/busses/i2c-ismt.c b/drivers/i2c/busses/i2c-ismt.c index 8477292e92c8..7aea28815d99 100644 --- a/drivers/i2c/busses/i2c-ismt.c +++ b/drivers/i2c/busses/i2c-ismt.c @@ -340,12 +340,15 @@ static int ismt_process_desc(const struct ismt_desc *desc, data->word = dma_buffer[0] | (dma_buffer[1] << 8); break; case I2C_SMBUS_BLOCK_DATA: - case I2C_SMBUS_I2C_BLOCK_DATA: if (desc->rxbytes != dma_buffer[0] + 1) return -EMSGSIZE; memcpy(data->block, dma_buffer, desc->rxbytes); break; + case I2C_SMBUS_I2C_BLOCK_DATA: + memcpy(&data->block[1], dma_buffer, desc->rxbytes); + data->block[0] = desc->rxbytes; + break; } return 0; } -- 2.11.0