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.
This patch does not solve the problem of lost console writes during
the kernel boot, but it does allow the usb_debug driver to function as
a usable interactive console.
Signed-off-by: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
---
drivers/usb/serial/usb_debug.c | 177 ++++++++++++++++++++++++++++++++++++++++
1 files changed, 177 insertions(+), 0 deletions(-)
diff --git a/drivers/usb/serial/usb_debug.c b/drivers/usb/serial/usb_debug.c
index 6c9cbb5..ec88c26 100644
--- a/drivers/usb/serial/usb_debug.c
+++ b/drivers/usb/serial/usb_debug.c
@@ -2,6 +2,7 @@
* USB Debug cable driver
*
* Copyright (C) 2006 Greg Kroah-Hartman <greg@xxxxxxxxx>
+ * Copyright (C) 2009 Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
@@ -15,7 +16,9 @@
#include <linux/usb.h>
#include <linux/usb/serial.h>
+#define URB_UPPER_LIMIT 42
#define USB_DEBUG_MAX_PACKET_SIZE 8
+static int debug;
static struct usb_device_id id_table [] = {
{ USB_DEVICE(0x0525, 0x127a) },
@@ -23,6 +26,11 @@ static struct usb_device_id id_table [] = {
};
MODULE_DEVICE_TABLE(usb, id_table);
+struct usb_debug_private {
+ spinlock_t tx_lock;
+ unsigned long tx_outstanding_urbs;
+};
+
static struct usb_driver debug_driver = {
.name = "debug",
.probe = usb_serial_probe,
@@ -38,6 +46,170 @@ static int usb_debug_open(struct tty_struct *tty, struct usb_serial_port *port,
return usb_serial_generic_open(tty, port, filp);
}
+static int usb_debug_port_remove(struct usb_serial_port *port)
+{
+ struct udb_debug_private *priv = usb_get_serial_port_data(port);
+
+ if (priv) {
+ usb_set_serial_port_data(port, NULL);
+ kfree(priv);
+ }
+ return 0;
+}
+static int usb_debug_port_probe(struct usb_serial_port *port)
+{
+ struct usb_debug_private *priv;
+
+ priv = kzalloc(sizeof(struct usb_debug_private), GFP_KERNEL);
+ if (!priv) {
+ dev_err(&port->dev, "%s- kmalloc(%Zd) failed.\n", __func__,
+ sizeof(struct usb_debug_private));
+ return -ENOMEM;
+ }
+ spin_lock_init(&priv->tx_lock);
+ if (port->write_urb) {
+ usb_free_urb(port->write_urb);
+ port->write_urb = NULL;
+ }
+ if (port->bulk_out_buffer) {
+ kfree(port->bulk_out_buffer);
+ port->bulk_out_buffer = NULL;
+ }
+
+ usb_set_serial_port_data(port, priv);
+ return 0;
+}
+
+static int usb_debug_write_room(struct tty_struct *tty)
+{
+ unsigned long flags;
+ struct usb_serial_port *port = tty->driver_data;
+ struct usb_debug_private *priv = usb_get_serial_port_data(port);
+ int room = 0;
+
+ dbg("%s - port %d", __func__, port->number);
+
+ spin_lock_irqsave(&priv->tx_lock, flags);
+ if (priv->tx_outstanding_urbs < URB_UPPER_LIMIT)
+ room = port->bulk_out_size;
+ spin_unlock_irqrestore(&priv->tx_lock, flags);
+
+ dbg("%s - returns %d", __func__, room);
+ return room;
+}
+
+static void usb_debug_write_bulk_callback(struct urb *urb)
+{
+ unsigned long flags;
+ struct usb_serial_port *port = urb->context;
+ struct usb_debug_private *priv;
+ int status = urb->status;
+
+ /* free up the transfer buffer, as usb_free_urb() does not do this */
+ kfree(urb->transfer_buffer);
+
+ dbg("%s - port %d", __func__, port->number);
+
+ if (status) {
+ dbg("nonzero write bulk status received: %d", status);
+ return;
+ }
+
+ priv = usb_get_serial_port_data(port);
+ if (!priv) {
+ dbg("%s - bad port private data pointer - exiting", __func__);
+ return;
+ }
+
+ spin_lock_irqsave(&priv->tx_lock, flags);
+ --priv->tx_outstanding_urbs;
+ spin_unlock_irqrestore(&priv->tx_lock, flags);
+
+ usb_serial_port_softint(port);
+}
+
+static int usb_debug_write(struct tty_struct *tty,
+ struct usb_serial_port *port, const unsigned char *buf, int count)
+{
+ struct usb_debug_private *priv = usb_get_serial_port_data(port);
+ unsigned long flags;
+ struct urb *urb;
+ unsigned char *buffer;
+ int status;
+ int towrite;
+ int bwrite = 0;
+
+ dbg("%s - port %d", __func__, port->number);
+
+ if (count == 0)
+ dbg("%s - write request of 0 bytes", __func__);
+
+ while (count > 0) {
+ spin_lock_irqsave(&priv->tx_lock, flags);
+ if (priv->tx_outstanding_urbs > URB_UPPER_LIMIT) {
+ spin_unlock_irqrestore(&priv->tx_lock, flags);
+ dbg("%s - write limit hit\n", __func__);
+ return bwrite;
+ }
+
+ priv->tx_outstanding_urbs++;
+ spin_unlock_irqrestore(&priv->tx_lock, flags);
+
+ towrite = (count > port->bulk_out_size) ?
+ port->bulk_out_size : count;
+
+ buffer = kmalloc(towrite, GFP_ATOMIC);
+ if (!buffer) {
+ dev_err(&port->dev,
+ "%s ran out of kernel memory for urb ...\n", __func__);
+ goto error_no_buffer;
+ }
+
+ urb = usb_alloc_urb(0, GFP_ATOMIC);
+ if (!urb) {
+ dev_err(&port->dev, "%s - no more free urbs\n",
+ __func__);
+ goto error_no_urb;
+ }
+
+ /* Copy data */
+ memcpy(buffer, buf + bwrite, towrite);
+ usb_serial_debug_data(debug, &port->dev, __func__,
+ towrite, buffer);
+ /* fill the buffer and send it */
+ usb_fill_bulk_urb(urb, port->serial->dev,
+ usb_sndbulkpipe(port->serial->dev,
+ port->bulk_out_endpointAddress),
+ buffer, towrite,
+ usb_debug_write_bulk_callback, port);
+
+ status = usb_submit_urb(urb, GFP_ATOMIC);
+ if (status) {
+ dev_err(&port->dev,
+ "%s - failed submitting write urb, error %d\n",
+ __func__, status);
+ goto error;
+ }
+
+ /* This urb is the responsibility of the host driver now */
+ usb_free_urb(urb);
+ dbg("%s write: %d", __func__, towrite);
+ count -= towrite;
+ bwrite += towrite;
+ }
+ return bwrite;
+
+error:
+ usb_free_urb(urb);
+error_no_urb:
+ kfree(buffer);
+error_no_buffer:
+ spin_lock_irqsave(&priv->tx_lock, flags);
+ priv->tx_outstanding_urbs--;
+ spin_unlock_irqrestore(&priv->tx_lock, flags);
+ return bwrite;
+}
+
static struct usb_serial_driver debug_device = {
.driver = {
.owner = THIS_MODULE,
@@ -46,6 +218,11 @@ static struct usb_serial_driver debug_device = {
.id_table = id_table,
.num_ports = 1,
.open = usb_debug_open,
+ .port_probe = usb_debug_port_probe,
+ .port_remove = usb_debug_port_remove,
+ .write = usb_debug_write,
+ .write_bulk_callback = usb_debug_write_bulk_callback,
+ .write_room = usb_debug_write_room,
};
static int __init debug_init(void)
--
1.6.3.rc0.1.gf800
--
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