USB: limit usbfs snooping of URB contents
The usbfs_snoop facility can be very useful for debugging problems
involving usbfs. However, it always prints out the entire contents of
every URB. When dealing with large quantities of data, this can be
less than helpful.
This patch ameliorates the situation by adding a module parameter to
usbcore for controlling the maximum number of bytes to print when
snooping an URB. This makes debugging much easier. For backward
compatibility, the default value is set unreasonably high.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 38ae877c..3d41faf 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -100,6 +100,11 @@
module_param(usbfs_snoop, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(usbfs_snoop, "true to log all usbfs traffic");
+static unsigned usbfs_snoop_max = 65536;
+module_param(usbfs_snoop_max, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(usbfs_snoop_max,
+ "maximum number of bytes to print while snooping");
+
#define snoop(dev, format, arg...) \
do { \
if (usbfs_snoop) \
@@ -392,6 +397,7 @@
ep, t, d, length, timeout_or_status);
}
+ data_len = min(data_len, usbfs_snoop_max);
if (data && data_len > 0) {
print_hex_dump(KERN_DEBUG, "data: ", DUMP_PREFIX_NONE, 32, 1,
data, data_len, 1);
@@ -402,7 +408,8 @@
{
int i, size;
- if (!usbfs_snoop)
+ len = min(len, usbfs_snoop_max);
+ if (!usbfs_snoop || len == 0)
return;
if (urb->num_sgs == 0) {