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authorSeymour, Shane M <shane.seymour@hpe.com>2015-10-12 04:31:17 +0000
committerJames Bottomley <JBottomley@Odin.com>2015-11-09 17:17:27 -0800
commitd9b43a10f0d04564c6e05de3728c3cbba64c644d (patch)
tree5661a5a688a92e9260af7e7d5cea0a04acca5cf3 /Documentation/scsi
parentc59ab4e5afade13fdb65efc99c07fb8455aecba5 (diff)
st: allow debug output to be enabled or disabled via sysfs
Change st driver to allow enabling or disabling debug output via sysfs file /sys/bus/scsi/drivers/st/debug_flag. Previously the only way to enable debug output was: 1. loading the driver with the module parameter debug_flag=1 2. an ioctl call (this method was also the only way to dynamically disable debug output). To use the ioctl you need a second tape drive (if you are actively testing the first tape drive) since a second process cannot open the first tape drive if it is in use. The this change is only functional if the value of the macro DEBUG in st.c is a non-zero value (which it is by default). Signed-off-by: Shane Seymour <shane.seymour@hpe.com> Reviewed-by: Laurence Oberman <oberman.l@gmail.com> Acked-by: Kai Mäkisara <kai.makisara@kolumbus.fi> Signed-off-by: James Bottomley <JBottomley@Odin.com>
Diffstat (limited to 'Documentation/scsi')
-rw-r--r--Documentation/scsi/st.txt4
1 files changed, 3 insertions, 1 deletions
diff --git a/Documentation/scsi/st.txt b/Documentation/scsi/st.txt
index f29fa550665a..b3211af63b79 100644
--- a/Documentation/scsi/st.txt
+++ b/Documentation/scsi/st.txt
@@ -569,7 +569,9 @@ Debugging code is now compiled in by default but debugging is turned off
with the kernel module parameter debug_flag defaulting to 0. Debugging
can still be switched on and off with an ioctl. To enable debug at
module load time add debug_flag=1 to the module load options, the
-debugging output is not voluminous.
+debugging output is not voluminous. Debugging can also be enabled
+and disabled by writing a '0' (disable) or '1' (enable) to the sysfs
+file /sys/bus/scsi/drivers/st/debug_flag.
If the tape seems to hang, I would be very interested to hear where
the driver is waiting. With the command 'ps -l' you can see the state