Re: [PATCH] Airprime driver improvements to allow full speed EvDO transfers

Andrew Morton
2006-06-30T07:10:38Z

On Fri, 30 Jun 2006 01:48:02 -0400
Andy Gay <andy@andynet.net> wrote:

>
> Adapted from an earlier patch by Greg KH <gregkh@suse.de>.
> That patch added multiple read urbs and larger transfer buffers to allow
> data transfers at full EvDO speed.
>
> This version includes additional device IDs and fixes a memory leak in
> the transfer buffer allocation.
>
> Some (maybe all?) of the supported devices present multiple bulk endpoints,
> the additional EPs can be used for control and status functions.
> This version allocates 3 EPs by default, that can be changed using
> the 'endpoints' module parameter.
>
> Tested with Sierra Wireless EM5625 and MC5720 embedded modules.
>
> Device ID (0x0c88, 0x17da) for the Kyocera Wireless KPC650/Passport
> was added but is not yet tested.
>
> ...
>
> +static void airprime_read_bulk_callback(struct urb *urb, struct pt_regs *regs)
> +{
> + struct usb_serial_port *port = urb->context;
> + unsigned char *data = urb->transfer_buffer;
> + struct tty_struct *tty;
> + int result;
> +
> + dbg("%s - port %d", __FUNCTION__, port->number);
> +
> + if (urb->status) {
> + dbg("%s - nonzero read bulk status received: %d",
> + __FUNCTION__, urb->status);
> + /* something happened, so free up the memory for this urb /*
> + if (urb->transfer_buffer) {
> + kfree (urb->transfer_buffer);
> + urb->transfer_buffer = NULL;
> + }
> + return;
> + }
> + usb_serial_debug_data(debug, &port->dev, __FUNCTION__, urb->actual_length, data);
> +
> + tty = port->tty;
> + if (tty && urb->actual_length) {
> + tty_buffer_request_room(tty, urb->actual_length);
> + tty_insert_flip_string(tty, data, urb->actual_length);

Is it correct to ignore the return value from those two functions?

> + tty_flip_buffer_push(tty);
> + }
> + /* should this use GFP_KERNEL? */
> + result = usb_submit_urb(urb, GFP_ATOMIC);

If possible, yep.

> ...
>
> +static int airprime_open(struct usb_serial_port *port, struct file *filp)
> +{
> + struct airprime_private *priv = usb_get_serial_port_data(port);
> + struct usb_serial *serial = port->serial;
> + struct urb *urb;
> + char *buffer;
> + int i;
> + int result = 0;
> +
> + dbg("%s - port %d", __FUNCTION__, port->number);
> +
> + /* initialize our private data structure if it isn't already created */
> + if (!priv) {
> + priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> + spin_lock_init(&priv->lock);
> + usb_set_serial_port_data(port, priv);
> + }
> + /* TODO handle error conditions better, right now we leak memory */
> + for (i = 0; i < NUM_READ_URBS; ++i) {
> + buffer = kmalloc(buffer_size, GFP_KERNEL);
> + if (!buffer) {
> + dev_err(&port->dev, "%s - out of memory.\n",
> + __FUNCTION__);
> + return -ENOMEM;
> + }
> + urb = usb_alloc_urb(0, GFP_KERNEL);
> + if (!urb) {
> + dev_err(&port->dev, "%s - no more urbs?\n",
> + __FUNCTION__);
> + return -ENOMEM;
> + }
> + usb_fill_bulk_urb(urb, serial->dev,
> + usb_rcvbulkpipe(serial->dev,
> + port->bulk_out_endpointAddress),
> + buffer, buffer_size,
> + airprime_read_bulk_callback, port);
> + result = usb_submit_urb(urb, GFP_KERNEL);
> + if (result) {
> + dev_err(&port->dev,
> + "%s - failed submitting read urb %d for port %d, error %d\n",
> + __FUNCTION__, i, port->number, result);
> + return result;
> + }
> + /* fun with reference counting, when this urb is finished, the
> + * host driver will free it up automatically */
> + /* don't do this here, we need the urb to stay around until the close
> + function can take care of it */
> + //usb_free_urb (urb);
> + /* instead remember this urb so we can kill it when the
> + port is closed */
> + priv->read_urbp[i] = urb;
> + }
> + return result;
> +}
> +

This function leaks memory all over the place if something goes wrong.

Please redesign it to have a single `return' statement. You'll find that'll
help avoid leaks now and during any later enhancements.

> +{
> + struct airprime_private *priv = usb_get_serial_port_data(port);
> + int i;
> +
> + dbg("%s - port %d", __FUNCTION__, port->number);
> +
> + /* killing the urb will invoke read_bulk_callback() with an error status,
> + so the transfer buffer will be freed there */
> + for (i = 0; i < NUM_READ_URBS; ++i) {
> + usb_kill_urb (priv->read_urbp[i]);
> + usb_free_urb (priv->read_urbp[i]);
> + }
> +
> + /* free up private structure? */

Yes please ;)

> +}
> +
> +static int airprime_write(struct usb_serial_port *port,
> + const unsigned char *buf, int count)
> +{
> + struct airprime_private *priv = usb_get_serial_port_data(port);
> + struct usb_serial *serial = port->serial;
> + struct urb *urb;
> + unsigned char *buffer;
> + unsigned long flags;
> + int status;
> + dbg("%s - port %d", __FUNCTION__, port->number);
> +
> + spin_lock_irqsave(&priv->lock, flags);
> + if (priv->outstanding_urbs > NUM_WRITE_URBS) {
> + spin_unlock_irqrestore(&priv->lock, flags);
> + dbg("%s - write limit hit\n", __FUNCTION__);
> + return 0;
> + }
> + spin_unlock_irqrestore(&priv->lock, flags);
> + buffer = kmalloc(count, GFP_ATOMIC);
> + if (!buffer) {
> + dev_err(&port->dev, "out of memory\n");
> + return -ENOMEM;
> + }
> + urb = usb_alloc_urb(0, GFP_ATOMIC);
> + if (!urb) {
> + dev_err(&port->dev, "no more free urbs\n");
> + kfree (buffer);
> + return -ENOMEM;
> + }
> + memcpy (buffer, buf, count);
> +
> + usb_serial_debug_data(debug, &port->dev, __FUNCTION__, count, buffer);
> +
> + usb_fill_bulk_urb(urb, serial->dev,
> + usb_sndbulkpipe(serial->dev,
> + port->bulk_out_endpointAddress),
> + buffer, count,
> + airprime_write_bulk_callback, port);
> +
> + /* send it down the pipe */
> + status = usb_submit_urb(urb, GFP_ATOMIC);
> + if (status) {
> + dev_err(&port->dev,
> + "%s - usb_submit_urb(write bulk) failed with status = %d\n",
> + __FUNCTION__, status);
> + count = status;
> + kfree (buffer);
> + } else {
> + spin_lock_irqsave(&priv->lock, flags);
> + ++priv->outstanding_urbs;
> + spin_unlock_irqrestore(&priv->lock, flags);
> + }
> + /* we are done with this urb, so let the host driver
> + * really free it when it is finished with it */
> + usb_free_urb (urb);
> + return count;
> +}

Is usb_serial_driver.write() really called in a context in which it is
forced to use GFP_ATOMIC?

Again, implementing this function as single-exit would make it easier to
maintain.

> +MODULE_PARM_DESC(debug, "Debug enabled or not");

Just "Debug enabled".

> +module_param(buffer_size, int, 0);
> +MODULE_PARM_DESC(buffer_size, "Size of the transfer buffers");

Units?