[PATCH v1 1/5] scsi: Adjust DBD setting in mode sense for caching mode page per LLD

[Can Guo <cang@codeaurora.org>]

Host sends MODE_SENSE_10 with caching mode page, to check if the device
supports the cache feature.
Some LLD standards requires DBD field to be set to 1.

This patch allows LLD to define the setting of DBD if required.

Change-Id: I0c8752c1888654942d6d7e6e0f6dc197033ac326
Signed-off-by: Can Guo <cang@codeaurora.org>
---
 drivers/scsi/sd.c        | 6 +++++-
 include/scsi/scsi_host.h | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index aab4ed8..6d8194f 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2629,6 +2629,7 @@ static int sd_try_rc16_first(struct scsi_device *sdp)
 {
 	int len = 0, res;
 	struct scsi_device *sdp = sdkp->device;
+	struct Scsi_Host *host = sdp->host;
 
 	int dbd;
 	int modepage;
@@ -2660,7 +2661,10 @@ static int sd_try_rc16_first(struct scsi_device *sdp)
 		dbd = 8;
 	} else {
 		modepage = 8;
-		dbd = 0;
+		if (host->set_dbd_for_caching)
+			dbd = 8;
+		else
+			dbd = 0;
 	}
 
 	/* cautiously ask */
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 2c3f0c5..3900987 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -650,6 +650,12 @@ struct Scsi_Host {
 	unsigned no_scsi2_lun_in_cdb:1;
 
 	/*
+	 * Set "DBD" field in mode_sense caching mode page in case it is
+	 * mandatory by LLD standard.
+	 */
+	unsigned set_dbd_for_caching:1;
+
+	/*
 	 * Optional work queue to be utilized by the transport
 	 */
 	char work_q_name[20];
-- 
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