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 <[email protected]>
Reviewed-by: Laurence Oberman <[email protected]>
Acked-by: Kai Mäkisara <[email protected]>
Signed-off-by: James Bottomley <[email protected]>
diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index b37b9b0..e0a1e52 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -4452,11 +4452,41 @@
}
static DRIVER_ATTR_RO(version);
+#if DEBUG
+static ssize_t debug_flag_store(struct device_driver *ddp,
+ const char *buf, size_t count)
+{
+/* We only care what the first byte of the data is the rest is unused.
+ * if it's a '1' we turn on debug and if it's a '0' we disable it. All
+ * other values have -EINVAL returned if they are passed in.
+ */
+ if (count > 0) {
+ if (buf[0] == '0') {
+ debugging = NO_DEBUG;
+ return count;
+ } else if (buf[0] == '1') {
+ debugging = 1;
+ return count;
+ }
+ }
+ return -EINVAL;
+}
+
+static ssize_t debug_flag_show(struct device_driver *ddp, char *buf)
+{
+ return scnprintf(buf, PAGE_SIZE, "%d\n", debugging);
+}
+static DRIVER_ATTR_RW(debug_flag);
+#endif
+
static struct attribute *st_drv_attrs[] = {
&driver_attr_try_direct_io.attr,
&driver_attr_fixed_buffer_size.attr,
&driver_attr_max_sg_segs.attr,
&driver_attr_version.attr,
+#if DEBUG
+ &driver_attr_debug_flag.attr,
+#endif
NULL,
};
ATTRIBUTE_GROUPS(st_drv);
