lkml.org 
[lkml]   [2017]   [Aug]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 1/2] i2c: ismt: Don't duplicate the receive length for block reads
Date
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@adiengineering.com>
Tested-by: Dan Priamo <danp@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
\
 
 \ /
  Last update: 2017-08-07 23:12    [W:0.164 / U:0.480 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site