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USB: serial: remove multi-urb write from generic driver

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Remove multi-urb write from the generic driver and simplify the
prepare_write_buffer prototype:

	int (*prepare_write_buffer)(struct usb_serial_port *port,
						void *dest, size_t size);

The default implementation simply fills dest with data from port write
fifo but drivers can override it if they need to process the outgoing
data (e.g. add headers).

Turn ftdi_sio into a generic fifo-based driver, which lowers CPU usage
significantly for small writes while retaining maximum throughput.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Johan Hovold
2010-05-05 23:58:13 +02:00
committed by Greg Kroah-Hartman
parent 27c7acf220
commit c23e5fc1f7
4 changed files with 47 additions and 175 deletions
Download Patch File Download Diff File Expand all files Collapse all files

57
drivers/usb/serial/ftdi_sio.c
View File

@@ -781,7 +781,7 @@ static void ftdi_close(struct usb_serial_port *port);
static void ftdi_dtr_rts(struct usb_serial_port *port, int on);
static void ftdi_process_read_urb(struct urb *urb);
static int ftdi_prepare_write_buffer(struct usb_serial_port *port,
void **dest, size_t size, const void *buf, size_t count);
void *dest, size_t size);
static void ftdi_set_termios(struct tty_struct *tty,
struct usb_serial_port *port, struct ktermios *old);
static int ftdi_tiocmget(struct tty_struct *tty, struct file *file);
@@ -808,8 +808,7 @@ static struct usb_serial_driver ftdi_sio_device = {
.id_table = id_table_combined,
.num_ports = 1,
.bulk_in_size = 512,
/* Must modify prepare_write_buffer if multi_urb_write is changed. */
.multi_urb_write = 1,
.bulk_out_size = 256,
.probe = ftdi_sio_probe,
.port_probe = ftdi_sio_port_probe,
.port_remove = ftdi_sio_port_remove,
@@ -1531,15 +1530,6 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
quirk->port_probe(priv);
priv->port = port;
/* Free port's existing write urb and transfer buffer. */
if (port->write_urb) {
usb_free_urb(port->write_urb);
port->write_urb = NULL;
}
kfree(port->bulk_out_buffer);
port->bulk_out_buffer = NULL;
usb_set_serial_port_data(port, priv);
ftdi_determine_type(port);
@@ -1734,8 +1724,7 @@ static void ftdi_close(struct usb_serial_port *port)
dbg("%s", __func__);
/* shutdown our bulk read */
usb_kill_urb(port->read_urb);
usb_serial_generic_close(port);
kref_put(&priv->kref, ftdi_sio_priv_release);
}
@@ -1747,40 +1736,34 @@ static void ftdi_close(struct usb_serial_port *port)
* The new devices do not require this byte
*/
static int ftdi_prepare_write_buffer(struct usb_serial_port *port,
void **dest, size_t size, const void *src, size_t count)
void *dest, size_t size)
{
struct ftdi_private *priv;
unsigned char *buffer;
int len;
int count;
unsigned long flags;
priv = usb_get_serial_port_data(port);
len = count;
if (priv->chip_type == SIO && count != 0)
len += ((count - 1) / (priv->max_packet_size - 1)) + 1;
buffer = kmalloc(len, GFP_ATOMIC);
if (!buffer) {
dev_err(&port->dev, "%s - could not allocate buffer\n",
__func__);
return -ENOMEM;
}
if (priv->chip_type == SIO) {
int i, msg_len;
unsigned char *buffer = dest;
int i, len, c;
for (i = 0; i < len; i += priv->max_packet_size) {
msg_len = min_t(int, len - i, priv->max_packet_size) - 1;
buffer[i] = (msg_len << 2) + 1;
memcpy(&buffer[i + 1], src, msg_len);
src += msg_len;
count = 0;
spin_lock_irqsave(&port->lock, flags);
for (i = 0; i < size - 1; i += priv->max_packet_size) {
len = min_t(int, size - i, priv->max_packet_size) - 1;
buffer[i] = (len << 2) + 1;
c = kfifo_out(&port->write_fifo, &buffer[i + 1], len);
if (!c)
break;
count += c + 1;
}
spin_unlock_irqrestore(&port->lock, flags);
} else {
memcpy(buffer, src, count);
count = kfifo_out_locked(&port->write_fifo, dest, size,
&port->lock);
}
*dest = buffer;
return count;
}