According to SPC-4, in a Mode Select, the PS bit in Mode Pages is
reserved and must be set to 0 by the driver. In the sd implementation,
function cache_type_store does a Mode Sense, which might set the PS bit
on the read buffer, followed by a Mode Select, which receives the same
buffer, without explicitly clearing the PS bit. So, in cases where
target supports saving the Mode Page to a non-volatile location, we end
up doing a Mode Select with the PS bit set, which could cause an illegal
request error if the target is checking this.
This was observed on a new firmware change, which was subsequently
reverted, but this changes sd.c to be more compliant with SPC-4.
This patch clears the PS bit in the buffer returned by Mode Select,
right before it is used in the Mode Select command.
Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxxxxxxx>
---
drivers/scsi/sd.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 3f37022..f724777 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -204,6 +204,7 @@ cache_type_store(struct device *dev, struct device_attribute *attr,
buffer_data[2] &= ~0x05;
buffer_data[2] |= wce << 2 | rcd;
sp = buffer_data[0] & 0x80 ? 1 : 0;
+ buffer_data[0] &= ~0x80;
if (scsi_mode_select(sdp, 1, sp, 8, buffer_data, len, SD_TIMEOUT,
SD_MAX_RETRIES, &data, &sshdr)) {
--
2.1.0
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