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| author | Seymour, Shane M <shane.seymour@hpe.com> | 2015-10-12 06:31:17 +0200 |
|---|---|---|
| committer | James Bottomley <JBottomley@Odin.com> | 2015-11-10 02:17:27 +0100 |
| commit | d9b43a10f0d04564c6e05de3728c3cbba64c644d (patch) | |
| tree | 5661a5a688a92e9260af7e7d5cea0a04acca5cf3 /Documentation | |
| parent | libfc: Use the correct function name in kernel-doc comment. (diff) | |
| download | linux-d9b43a10f0d04564c6e05de3728c3cbba64c644d.tar.xz linux-d9b43a10f0d04564c6e05de3728c3cbba64c644d.zip | |
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')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-driver-st | 12 | ||||
| -rw-r--r-- | Documentation/scsi/st.txt | 4 |
2 files changed, 15 insertions, 1 deletions
diff --git a/Documentation/ABI/testing/sysfs-driver-st b/Documentation/ABI/testing/sysfs-driver-st new file mode 100644 index 000000000000..ba5d77008a85 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-driver-st @@ -0,0 +1,12 @@ +What: /sys/bus/scsi/drivers/st/debug_flag +Date: October 2015 +Kernel Version: ?.? +Contact: shane.seymour@hpe.com +Description: + This file allows you to turn debug output from the st driver + off if you write a '0' to the file or on if you write a '1'. + Note that debug output requires that the module be compiled + with the #define DEBUG set to a non-zero value (this is the + default). If DEBUG is set to 0 then this file will not + appear in sysfs as its presence is conditional upon debug + output support being compiled into the module. 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 |