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Commit b6c159a9 authored by Stephen Douthit's avatar Stephen Douthit Committed by Wolfram Sang
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i2c: ismt: Don't duplicate the receive length for block reads 



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: default avatarStephen Douthit <stephend@adiengineering.com>
Tested-by: default avatarDan Priamo <danp@adiengineering.com>
Acked-by: default avatarNeil Horman <nhorman@tuxdriver.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
parent cc4a41fe

drivers/i2c/busses/i2c-ismt.c

+2 −2
Original line number Original line Diff line number Diff line
@@ -341,8 +341,8 @@ static int ismt_process_desc(const struct ismt_desc *desc, 
			break;

			break;

		case I2C_SMBUS_BLOCK_DATA:

		case I2C_SMBUS_BLOCK_DATA:

		case I2C_SMBUS_I2C_BLOCK_DATA:

		case I2C_SMBUS_I2C_BLOCK_DATA:

			memcpy(&data->block[1], dma_buffer, desc->rxbytes);

			memcpy(data->block, dma_buffer, desc->rxbytes);

			data->block[0] = desc->rxbytes;

			data->block[0] = desc->rxbytes - 1;

			break;

			break;

		}

		}

		return 0;

		return 0;