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authorJason Wessel <jason.wessel@windriver.com>2009-05-11 15:24:07 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2009-06-15 21:44:45 -0700
commit715b1dc01fe44537e8fce9566e4bb48d6821d84b (patch)
treeb1fc0b5c61a7317e7104468afddad544fb3fc34c /drivers/usb/serial/usb_debug.c
parentb0cda8c5f7b652c6c27bcb3891d174534d2f1a91 (diff)
USB: usb_debug, usb_generic_serial: implement multi urb write
The usb_debug driver, when used as the console, will always fail to insert the carriage return and new line sequence as well as randomly drop console output. This is a result of only having the single write_urb and that the tty layer will have a lock that prevents the processing of the back to back urb requests. The solution is to allow more than one urb to be outstanding and have a slightly deeper transmit queue. The idea and some code is borrowed from the ftdi_sio usb driver. The generic usb serial driver was modified so as to allow the classic method of 1 write urb, or a multi write urb scheme with N allowed outstanding urbs where N is controlled by max_in_flight_urbs. When max_in_flight_urbs in a "struct usb_serial_driver" is non zero the multi write urb scheme will be used. The size of 4000 was selected for the usb_debug driver so that the driver lowers possibility of losing the queued console messages during the kernel startup. Signed-off-by: Jason Wessel <jason.wessel@windriver.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/serial/usb_debug.c')
-rw-r--r--drivers/usb/serial/usb_debug.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/usb/serial/usb_debug.c b/drivers/usb/serial/usb_debug.c
index 6c9cbb59552..a9427a8b867 100644
--- a/drivers/usb/serial/usb_debug.c
+++ b/drivers/usb/serial/usb_debug.c
@@ -15,6 +15,7 @@
#include <linux/usb.h>
#include <linux/usb/serial.h>
+#define URB_DEBUG_MAX_IN_FLIGHT_URBS 4000
#define USB_DEBUG_MAX_PACKET_SIZE 8
static struct usb_device_id id_table [] = {
@@ -46,6 +47,7 @@ static struct usb_serial_driver debug_device = {
.id_table = id_table,
.num_ports = 1,
.open = usb_debug_open,
+ .max_in_flight_urbs = URB_DEBUG_MAX_IN_FLIGHT_URBS,
};
static int __init debug_init(void)