From d9b43a10f0d04564c6e05de3728c3cbba64c644d Mon Sep 17 00:00:00 2001 From: "Seymour, Shane M" Date: Mon, 12 Oct 2015 04:31:17 +0000 Subject: st: allow debug output to be enabled or disabled via sysfs MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Laurence Oberman Acked-by: Kai Mäkisara Signed-off-by: James Bottomley --- Documentation/ABI/testing/sysfs-driver-st | 12 ++++++++++++ Documentation/scsi/st.txt | 4 +++- 2 files changed, 15 insertions(+), 1 deletion(-) create mode 100644 Documentation/ABI/testing/sysfs-driver-st (limited to 'Documentation') 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 -- cgit v1.2.3