message.c

linux-2.6.15.6

	for (i = 0; i < io->entries; i++) {
		unsigned		len;

		io->urbs [i] = usb_alloc_urb (0, mem_flags);
		if (!io->urbs [i]) {
			io->entries = i;
			goto nomem;
		}

		io->urbs [i]->dev = NULL;
		io->urbs [i]->pipe = pipe;
		io->urbs [i]->interval = period;
		io->urbs [i]->transfer_flags = urb_flags;

		io->urbs [i]->complete = sg_complete;
		io->urbs [i]->context = io;
		io->urbs [i]->status = -EINPROGRESS;
		io->urbs [i]->actual_length = 0;

		if (dma) {
			/* hc may use _only_ transfer_dma */
			io->urbs [i]->transfer_dma = sg_dma_address (sg + i);
			len = sg_dma_len (sg + i);
		} else {
			/* hc may use _only_ transfer_buffer */
			io->urbs [i]->transfer_buffer =
				page_address (sg [i].page) + sg [i].offset;
			len = sg [i].length;
		}

		if (length) {
			len = min_t (unsigned, len, length);
			length -= len;
			if (length == 0)
				io->entries = i + 1;
		}
		io->urbs [i]->transfer_buffer_length = len;
	}
	io->urbs [--i]->transfer_flags &= ~URB_NO_INTERRUPT;

	/* transaction state */
	io->status = 0;
	io->bytes = 0;
	init_completion (&io->complete);
	return 0;

nomem:
	sg_clean (io);
	return -ENOMEM;
}


/**
 * usb_sg_wait - synchronously execute scatter/gather request
 * @io: request block handle, as initialized with usb_sg_init().
 * 	some fields become accessible when this call returns.
 * Context: !in_interrupt ()
 *
 * This function blocks until the specified I/O operation completes.  It
 * leverages the grouping of the related I/O requests to get good transfer
 * rates, by queueing the requests.  At higher speeds, such queuing can
 * significantly improve USB throughput.
 *
 * There are three kinds of completion for this function.
 * (1) success, where io->status is zero.  The number of io->bytes
 *     transferred is as requested.
 * (2) error, where io->status is a negative errno value.  The number
 *     of io->bytes transferred before the error is usually less
 *     than requested, and can be nonzero.
 * (3) cancellation, a type of error with status -ECONNRESET that
 *     is initiated by usb_sg_cancel().
 *
 * When this function returns, all memory allocated through usb_sg_init() or
 * this call will have been freed.  The request block parameter may still be
 * passed to usb_sg_cancel(), or it may be freed.  It could also be
 * reinitialized and then reused.
 *
 * Data Transfer Rates:
 *
 * Bulk transfers are valid for full or high speed endpoints.
 * The best full speed data rate is 19 packets of 64 bytes each
 * per frame, or 1216 bytes per millisecond.
 * The best high speed data rate is 13 packets of 512 bytes each
 * per microframe, or 52 KBytes per millisecond.
 *
 * The reason to use interrupt transfers through this API would most likely
 * be to reserve high speed bandwidth, where up to 24 KBytes per millisecond
 * could be transferred.  That capability is less useful for low or full
 * speed interrupt endpoints, which allow at most one packet per millisecond,
 * of at most 8 or 64 bytes (respectively).
 */
void usb_sg_wait (struct usb_sg_request *io)
{
	int		i, entries = io->entries;

	/* queue the urbs.  */
	spin_lock_irq (&io->lock);
	for (i = 0; i < entries && !io->status; i++) {
		int	retval;

		io->urbs [i]->dev = io->dev;
		retval = usb_submit_urb (io->urbs [i], SLAB_ATOMIC);

		/* after we submit, let completions or cancelations fire;
		 * we handshake using io->status.
		 */
		spin_unlock_irq (&io->lock);
		switch (retval) {
			/* maybe we retrying will recover */
		case -ENXIO:	// hc didn't queue this one
		case -EAGAIN:
		case -ENOMEM:
			io->urbs[i]->dev = NULL;
			retval = 0;
			i--;
			yield ();
			break;

			/* no error? continue immediately.
			 *
			 * NOTE: to work better with UHCI (4K I/O buffer may
			 * need 3K of TDs) it may be good to limit how many
			 * URBs are queued at once; N milliseconds?
			 */
		case 0:
			cpu_relax ();
			break;

			/* fail any uncompleted urbs */
		default:
			io->urbs [i]->dev = NULL;
			io->urbs [i]->status = retval;
			dev_dbg (&io->dev->dev, "%s, submit --> %d\n",
				__FUNCTION__, retval);
			usb_sg_cancel (io);
		}
		spin_lock_irq (&io->lock);
		if (retval && (io->status == 0 || io->status == -ECONNRESET))
			io->status = retval;
	}
	io->count -= entries - i;
	if (io->count == 0)
		complete (&io->complete);
	spin_unlock_irq (&io->lock);

	/* OK, yes, this could be packaged as non-blocking.
	 * So could the submit loop above ... but it's easier to
	 * solve neither problem than to solve both!
	 */
	wait_for_completion (&io->complete);

	sg_clean (io);
}

/**
 * usb_sg_cancel - stop scatter/gather i/o issued by usb_sg_wait()
 * @io: request block, initialized with usb_sg_init()
 *
 * This stops a request after it has been started by usb_sg_wait().
 * It can also prevents one initialized by usb_sg_init() from starting,
 * so that call just frees resources allocated to the request.
 */
void usb_sg_cancel (struct usb_sg_request *io)
{
	unsigned long	flags;

	spin_lock_irqsave (&io->lock, flags);

	/* shut everything down, if it didn't already */
	if (!io->status) {
		int	i;

		io->status = -ECONNRESET;
		spin_unlock (&io->lock);
		for (i = 0; i < io->entries; i++) {
			int	retval;

			if (!io->urbs [i]->dev)
				continue;
			retval = usb_unlink_urb (io->urbs [i]);
			if (retval != -EINPROGRESS && retval != -EBUSY)
				dev_warn (&io->dev->dev, "%s, unlink --> %d\n",
					__FUNCTION__, retval);
		}
		spin_lock (&io->lock);
	}
	spin_unlock_irqrestore (&io->lock, flags);
}

/*-------------------------------------------------------------------*/

/**
 * usb_get_descriptor - issues a generic GET_DESCRIPTOR request
 * @dev: the device whose descriptor is being retrieved
 * @type: the descriptor type (USB_DT_*)
 * @index: the number of the descriptor
 * @buf: where to put the descriptor
 * @size: how big is "buf"?
 * Context: !in_interrupt ()
 *
 * Gets a USB descriptor.  Convenience functions exist to simplify
 * getting some types of descriptors.  Use
 * usb_get_string() or usb_string() for USB_DT_STRING.
 * Device (USB_DT_DEVICE) and configuration descriptors (USB_DT_CONFIG)
 * are part of the device structure.
 * In addition to a number of USB-standard descriptors, some
 * devices also use class-specific or vendor-specific descriptors.
 *
 * This call is synchronous, and may not be used in an interrupt context.
 *
 * Returns the number of bytes received on success, or else the status code
 * returned by the underlying usb_control_msg() call.
 */
int usb_get_descriptor(struct usb_device *dev, unsigned char type, unsigned char index, void *buf, int size)
{
	int i;
	int result;
	
	memset(buf,0,size);	// Make sure we parse really received data

	for (i = 0; i < 3; ++i) {
		/* retry on length 0 or stall; some devices are flakey */
		result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
				USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
				(type << 8) + index, 0, buf, size,
				USB_CTRL_GET_TIMEOUT);
		if (result == 0 || result == -EPIPE)
			continue;
		if (result > 1 && ((u8 *)buf)[1] != type) {
			result = -EPROTO;
			continue;
		}
		break;
	}
	return result;
}

/**
 * usb_get_string - gets a string descriptor
 * @dev: the device whose string descriptor is being retrieved
 * @langid: code for language chosen (from string descriptor zero)
 * @index: the number of the descriptor
 * @buf: where to put the string
 * @size: how big is "buf"?
 * Context: !in_interrupt ()
 *
 * Retrieves a string, encoded using UTF-16LE (Unicode, 16 bits per character,
 * in little-endian byte order).
 * The usb_string() function will often be a convenient way to turn
 * these strings into kernel-printable form.
 *
 * Strings may be referenced in device, configuration, interface, or other
 * descriptors, and could also be used in vendor-specific ways.
 *
 * This call is synchronous, and may not be used in an interrupt context.
 *
 * Returns the number of bytes received on success, or else the status code
 * returned by the underlying usb_control_msg() call.
 */
int usb_get_string(struct usb_device *dev, unsigned short langid,
		unsigned char index, void *buf, int size)
{
	int i;
	int result;

	for (i = 0; i < 3; ++i) {
		/* retry on length 0 or stall; some devices are flakey */
		result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
			USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
			(USB_DT_STRING << 8) + index, langid, buf, size,
			USB_CTRL_GET_TIMEOUT);
		if (!(result == 0 || result == -EPIPE))
			break;
	}
	return result;
}

static void usb_try_string_workarounds(unsigned char *buf, int *length)
{
	int newlength, oldlength = *length;

	for (newlength = 2; newlength + 1 < oldlength; newlength += 2)
		if (!isprint(buf[newlength]) || buf[newlength + 1])
			break;

	if (newlength > 2) {
		buf[0] = newlength;
		*length = newlength;
	}
}

static int usb_string_sub(struct usb_device *dev, unsigned int langid,
		unsigned int index, unsigned char *buf)
{
	int rc;

	/* Try to read the string descriptor by asking for the maximum
	 * possible number of bytes */
	rc = usb_get_string(dev, langid, index, buf, 255);

	/* If that failed try to read the descriptor length, then
	 * ask for just that many bytes */
	if (rc < 2) {
		rc = usb_get_string(dev, langid, index, buf, 2);
		if (rc == 2)
			rc = usb_get_string(dev, langid, index, buf, buf[0]);
	}

	if (rc >= 2) {
		if (!buf[0] && !buf[1])
			usb_try_string_workarounds(buf, &rc);

		/* There might be extra junk at the end of the descriptor */
		if (buf[0] < rc)
			rc = buf[0];

		rc = rc - (rc & 1); /* force a multiple of two */
	}

	if (rc < 2)
		rc = (rc < 0 ? rc : -EINVAL);

	return rc;
}

/**
 * usb_string - returns ISO 8859-1 version of a string descriptor
 * @dev: the device whose string descriptor is being retrieved
 * @index: the number of the descriptor
 * @buf: where to put the string
 * @size: how big is "buf"?
 * Context: !in_interrupt ()
 * 
 * This converts the UTF-16LE encoded strings returned by devices, from
 * usb_get_string_descriptor(), to null-terminated ISO-8859-1 encoded ones
 * that are more usable in most kernel contexts.  Note that all characters
 * in the chosen descriptor that can't be encoded using ISO-8859-1
 * are converted to the question mark ("?") character, and this function
 * chooses strings in the first language supported by the device.
 *
 * The ASCII (or, redundantly, "US-ASCII") character set is the seven-bit
 * subset of ISO 8859-1. ISO-8859-1 is the eight-bit subset of Unicode,
 * and is appropriate for use many uses of English and several other
 * Western European languages.  (But it doesn't include the "Euro" symbol.)
 *
 * This call is synchronous, and may not be used in an interrupt context.
 *
 * Returns length of the string (>= 0) or usb_control_msg status (< 0).
 */
int usb_string(struct usb_device *dev, int index, char *buf, size_t size)
{
	unsigned char *tbuf;
	int err;
	unsigned int u, idx;

	if (dev->state == USB_STATE_SUSPENDED)
		return -EHOSTUNREACH;
	if (size <= 0 || !buf || !index)
		return -EINVAL;
	buf[0] = 0;
	tbuf = kmalloc(256, GFP_KERNEL);
	if (!tbuf)
		return -ENOMEM;

	/* get langid for strings if it's not yet known */
	if (!dev->have_langid) {
		err = usb_string_sub(dev, 0, 0, tbuf);
		if (err < 0) {
			dev_err (&dev->dev,
				"string descriptor 0 read error: %d\n",
				err);
			goto errout;
		} else if (err < 4) {