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 <steph...@adiengineering.com>
Tested-by: Dan Priamo <d...@adiengineering.com>
---
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
