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 --- include/linux/usb/serial.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include') diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h index 8cdfed738fe..e2938fd179e 100644 --- a/include/linux/usb/serial.h +++ b/include/linux/usb/serial.h @@ -91,6 +91,9 @@ struct usb_serial_port { int write_urb_busy; __u8 bulk_out_endpointAddress; + int tx_bytes_flight; + int urbs_in_flight; + wait_queue_head_t write_wait; struct work_struct work; char throttled; @@ -207,6 +210,7 @@ struct usb_serial_driver { struct device_driver driver; struct usb_driver *usb_driver; struct usb_dynids dynids; + int max_in_flight_urbs; int (*probe)(struct usb_serial *serial, const struct usb_device_id *id); int (*attach)(struct usb_serial *serial); -- cgit v1.2.3