From: Weiping Zhang <zhangweiping@didichuxing.com>
Date: Mon, 26 Feb 2018 22:08:28 +0800
Subject: [PATCH] scsi: sd: Documentation: add sd-parameters.txt
Git-commit: 18d595bf9de99a0f092d8522da42df8b09ef5c2f
Patch-mainline: v4.17-rc1
References: bsc#1118139
Add a file for documenting SCSI sd module parameters and describe the
cache_type setting.
[mkp: tweaked text a bit]
Signed-off-by: Weiping Zhang <zhangweiping@didichuxing.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Hannes Reinecke <hare@suse.com>
---
Documentation/scsi/sd-parameters.txt | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
create mode 100644 Documentation/scsi/sd-parameters.txt
diff --git a/Documentation/scsi/sd-parameters.txt b/Documentation/scsi/sd-parameters.txt
new file mode 100644
index 000000000000..8e5af00d88e7
--- /dev/null
+++ b/Documentation/scsi/sd-parameters.txt
@@ -0,0 +1,22 @@
+Linux SCSI Disk Driver (sd) Parameters
+======================================
+
+cache_type (RW)
+---------------
+Enable/disable drive write & read cache.
+
+ cache_type string | WCE RCD | Write cache | Read cache
+----------------------------+---------+-------------+------------
+ write through | 0 0 | off | on
+ none | 0 1 | off | off
+ write back | 1 0 | on | on
+ write back, no read (daft) | 1 1 | on | off
+
+To set cache type to "write back" and save this setting to the drive:
+
+ # echo "write back" > cache_type
+
+To modify the caching mode without making the change persistent, prepend
+"temporary " to the cache type string. E.g.:
+
+ # echo "temporary write back" > cache_type
--
2.12.3