According to Table 15-14 of the C2000 EDS (Intel doc #510524) the rx data pointed to by the descriptor dptr contains the byte count. desc->rxbytes reports all bytes read on the wire, including the "byte count" byte. So if a device sends 4 bytes in response to a block read, on the wire and in the DMA buffer we see: count data1 data2 data3 data4 0x04 0xde 0xad 0xbe 0xef That's what we want to return in data->block to the next level. Instead we were actually prefixing that with desc->rxbytes: bad count count data1 data2 data3 data4 0x05 0x04 0xde 0xad 0xbe 0xef This was discovered while developing a BMC solution relying on the ipmi_ssif.c driver which was trying to interpret the bogus length field as part of the IPMI response. Signed-off-by: Stephen Douthit <stephend@xxxxxxxxxxxxxxxxxx> Tested-by: Dan Priamo <danp@xxxxxxxxxxxxxxxxxx> --- drivers/i2c/busses/i2c-ismt.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/i2c/busses/i2c-ismt.c b/drivers/i2c/busses/i2c-ismt.c index e98e44e..9af2337 100644 --- a/drivers/i2c/busses/i2c-ismt.c +++ b/drivers/i2c/busses/i2c-ismt.c @@ -341,8 +341,8 @@ static int ismt_process_desc(const struct ismt_desc *desc, break; case I2C_SMBUS_BLOCK_DATA: case I2C_SMBUS_I2C_BLOCK_DATA: - memcpy(&data->block[1], dma_buffer, desc->rxbytes); - data->block[0] = desc->rxbytes; + memcpy(data->block, dma_buffer, desc->rxbytes); + data->block[0] = desc->rxbytes - 1; break; } return 0; -- 2.7.5
