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Subject[PATCH][RFC 20/23]: Documentation for scst_local driver
This patch contains documentation for scst_local driver.

Signed-off-by: Richard Sharpe <>
Signed-off-by: Vladislav Bolkhovitin <>
Documentation/scst/README.scst_local | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 95 insertions(+)

diff -uprN orig/linux-2.6.27/Documentation/scst/README.scst_local linux-2.6.27/Documentation/scst/README.scst_local
--- orig/linux-2.6.27/Documentation/scst/README.scst_local
+++ linux-2.6.27/Documentation/scst/README.scst_local
@@ -0,0 +1,95 @@
+SCST Debug ...
+Richard Sharpe, 30-Nov-2008
+This is the SCST Local driver. Its function is to allow you to access devices
+that are exported via SCST directly on the same Linux system that they are
+exported from.
+No assumptions are made in the code about the device types on the target, so
+any device handlers that you load in SCST should be visible, including tapes
+and so forth.
+To build, simply issue 'make' in the scst-local directory.
+Try 'modinfo scst_local' for a listing of module parameters so far.
+NOTE! This is now part of scst and supports being built in the scst tree.
+Here is how I have used it so far:
+1. Load up scst:
+ modprobe scst
+ modprobe scst_vdisk
+2. Create a virtual disk (or your own device handler):
+ dd if=/dev/zero of=/some/path/vdisk1.img bs=16384 count=1000000
+# dd if=/dev/zero of=/some/path/vdisk2.img bs=16384 count=1000000
+ echo "open vm_disk1 /some/path/vdisk1.img" > /proc/scsi_tgt/vdisk/vdisk
+# echo "open vm_disk2 /some/path/vdisk2.img" > /proc/scsi_tgt/vdisk/vdisk
+ echo "add vm_disk1 0" > /proc/scsi_tgt/groups/Default/devices
+# echo "add vm_disk2 1" > /proc/scsi_tgt/groups/Default/devices
+3. Load the scst_local driver:
+ insmod scst_local
+# insmod scst_local max_luns=8
+4. Check what you have
+ cat /proc/scsi/scsi
+ Attached devices:
+ Host: scsi0 Channel: 00 Id: 00 Lun: 00
+ Vendor: ATA Model: ST9320320AS Rev: 0303
+ Type: Direct-Access ANSI SCSI revision: 05
+ Host: scsi4 Channel: 00 Id: 00 Lun: 00
+ Vendor: TSSTcorp Model: CD/DVDW TS-L632D Rev: TO04
+ Type: CD-ROM ANSI SCSI revision: 05
+ Host: scsi7 Channel: 00 Id: 00 Lun: 00
+ Vendor: SCST_FIO Model: vm_disk1 Rev: 101
+ Type: Direct-Access ANSI SCSI revision: 04
+5. Have fun.
+Some of this was coded while in Santa Clara, some in Bangalore, and some in
+Hyderabad. Noe doubt some will be coded on the way back to Santa Clara.
+The code still has bugs, so if you encounter any, email me the fixes at:
+I am thinking of renaming this to something more interesting.
+6. Change log
+V0.1 24-Sep-2008 (Hyderabad) Initial coding, pretty chatty and messy,
+ but worked.
+V0.2 25-Sep-2008 (Hong Kong) Cleaned up the code a lot, reduced the log
+ chatter, fixed a bug where multiple LUNs did not
+ work. Also, added logging control. Tested with
+ five virtual disks. They all came up as /dev/sdb
+ through /dev/sdf and I could dd to them. Also
+ fixed a bug preventing multiple adapters.
+V0.3 26-Sep-2008 (Santa Clara) Added back a copyright plus cleaned up some
+ unused functions and structures.
+V0.4 5-Oct-2008 (Santa Clara) Changed name to scst_local as suggested, cleaned
+ up some unused variables (made them used) and
+ change allocation to a kmem_cache pool.
+V0.5 5-Oct-2008 (Santa Clara) Added mgmt commands to handle dev reset and
+ aborts. Not sure if aborts works. Also corrected
+ the version info and renamed readme to README.
+V0.6 7-Oct-2008 (Santa Clara) Removed some redundant code and made some
+ changes suggested by Vladislav.
+V0.7 11-Oct-2008 (Santa Clara) Moved into the scst tree. Cleaned up some
+ unused functions, used TRACE macros etc.
+V0.9 30-Nov-2008 (Mtn View) Cleaned up an additional problem with symbols not
+ being defined in older version of the kernel. Also
+ fixed some English and cleaned up this doc.

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