From 715b1dc01fe44537e8fce9566e4bb48d6821d84b Mon Sep 17 00:00:00 2001 From: Jason Wessel Date: Mon, 11 May 2009 15:24:07 -0500 Subject: 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 Signed-off-by: Greg Kroah-Hartman --- drivers/usb/serial/usb_debug.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/usb/serial/usb_debug.c') diff --git a/drivers/usb/serial/usb_debug.c b/drivers/usb/serial/usb_debug.c index 6c9cbb59552a..a9427a8b8672 100644 --- a/drivers/usb/serial/usb_debug.c +++ b/drivers/usb/serial/usb_debug.c @@ -15,6 +15,7 @@ #include #include +#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) -- cgit v1.2.3