usb驱动开发14之设备生命线

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

/**
 * usb_submit_urb - issue an asynchronous transfer request for an endpoint
 * @urb: pointer to the urb describing the request
 * @mem_flags: the type of memory to allocate, see kmalloc() for a list
 *	of valid options for this.
 *
 * This submits a transfer request, and transfers control of the URB
 * describing that request to the USB subsystem.  Request completion will
 * be indicated later, asynchronously, by calling the completion handler.
 * The three types of completion are success, error, and unlink
 * (a software-induced fault, also called "request cancellation").  
 *
 * URBs may be submitted in interrupt context.
 *
 * The caller must have correctly initialized the URB before submitting
 * it.  Functions such as usb_fill_bulk_urb() and usb_fill_control_urb() are
 * available to ensure that most fields are correctly initialized, for
 * the particular kind of transfer, although they will not initialize
 * any transfer flags.
 *
 * Successful submissions return 0; otherwise this routine returns a
 * negative error number.  If the submission is successful, the complete()
 * callback from the URB will be called exactly once, when the USB core and
 * Host Controller Driver (HCD) are finished with the URB.  When the completion
 * function is called, control of the URB is returned to the device
 * driver which issued the request.  The completion handler may then
 * immediately free or reuse that URB.
 *
 * With few exceptions, USB device drivers should never access URB fields
 * provided by usbcore or the HCD until its complete() is called.
 * The exceptions relate to periodic transfer scheduling.  For both
 * interrupt and isochronous urbs, as part of successful URB submission
 * urb->interval is modified to reflect the actual transfer period used
 * (normally some power of two units).  And for isochronous urbs,
 * urb->start_frame is modified to reflect when the URB‘s transfers were
 * scheduled to start.  Not all isochronous transfer scheduling policies
 * will work, but most host controller drivers should easily handle ISO
 * queues going from now until 10-200 msec into the future.
 *
 * For control endpoints, the synchronous usb_control_msg() call is
 * often used (in non-interrupt context) instead of this call.
 * That is often used through convenience wrappers, for the requests
 * that are standardized in the USB 2.0 specification.  For bulk
 * endpoints, a synchronous usb_bulk_msg() call is available.
 *
 * Request Queuing:
 *
 * URBs may be submitted to endpoints before previous ones complete, to
 * minimize the impact of interrupt latencies and system overhead on data
 * throughput.  With that queuing policy, an endpoint‘s queue would never
 * be empty.  This is required for continuous isochronous data streams,
 * and may also be required for some kinds of interrupt transfers. Such
 * queuing also maximizes bandwidth utilization by letting USB controllers
 * start work on later requests before driver software has finished the
 * completion processing for earlier (successful) requests.
 *
 * As of Linux 2.6, all USB endpoint transfer queues support depths greater
 * than one.  This was previously a HCD-specific behavior, except for ISO
 * transfers.  Non-isochronous endpoint queues are inactive during cleanup
 * after faults (transfer errors or cancellation).
 *
 * Reserved Bandwidth Transfers:
 *
 * Periodic transfers (interrupt or isochronous) are performed repeatedly,
 * using the interval specified in the urb.  Submitting the first urb to
 * the endpoint reserves the bandwidth necessary to make those transfers.
 * If the USB subsystem can‘t allocate sufficient bandwidth to perform
 * the periodic request, submitting such a periodic request should fail.
 *
 * Device drivers must explicitly request that repetition, by ensuring that
 * some URB is always on the endpoint‘s queue (except possibly for short
 * periods during completion callacks).  When there is no longer an urb
 * queued, the endpoint‘s bandwidth reservation is canceled.  This means
 * drivers can use their completion handlers to ensure they keep bandwidth
 * they need, by reinitializing and resubmitting the just-completed urb
 * until the driver longer needs that periodic bandwidth.
 *
 * Memory Flags:
 *
 * The general rules for how to decide which mem_flags to use
 * are the same as for kmalloc.  There are four
 * different possible values; GFP_KERNEL, GFP_NOFS, GFP_NOIO and
 * GFP_ATOMIC.
 *
 * GFP_NOFS is not ever used, as it has not been implemented yet.
 *
 * GFP_ATOMIC is used when
 *   (a) you are inside a completion handler, an interrupt, bottom half,
 *       tasklet or timer, or
 *   (b) you are holding a spinlock or rwlock (does not apply to
 *       semaphores), or
 *   (c) current->state != TASK_RUNNING, this is the case only after
 *       you‘ve changed it.
 * 
 * GFP_NOIO is used in the block io path and error handling of storage
 * devices.
 *
 * All other situations use GFP_KERNEL.
 *
 * Some more specific rules for mem_flags can be inferred, such as
 *  (1) start_xmit, timeout, and receive methods of network drivers must
 *      use GFP_ATOMIC (they are called with a spinlock held);
 *  (2) queuecommand methods of scsi drivers must use GFP_ATOMIC (also
 *      called with a spinlock held);
 *  (3) If you use a kernel thread with a network driver you must use
 *      GFP_NOIO, unless (b) or (c) apply;
 *  (4) after you have done a down() you can use GFP_KERNEL, unless (b) or (c)
 *      apply or your are in a storage driver‘s block io path;
 *  (5) USB probe and disconnect can use GFP_KERNEL unless (b) or (c) apply; and
 *  (6) changing firmware on a running storage or net device uses
 *      GFP_NOIO, unless b) or c) apply
 *
 */
int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
{
	int			pipe, temp, max;
	struct usb_device	*dev;
	int			is_out;

	if (!urb || urb->hcpriv || !urb->complete)
		return -EINVAL;
	if (!(dev = urb->dev) ||
	    (dev->state < USB_STATE_DEFAULT) ||
	    (!dev->bus) || (dev->devnum <= 0))
		return -ENODEV;
	if (dev->bus->controller->power.power_state.event != PM_EVENT_ON
			|| dev->state == USB_STATE_SUSPENDED)
		return -EHOSTUNREACH;

	urb->status = -EINPROGRESS;
	urb->actual_length = 0;

	/* Lots of sanity checks, so HCDs can rely on clean data
	 * and don‘t need to duplicate tests
	 */
	pipe = urb->pipe;
	temp = usb_pipetype(pipe);
	is_out = usb_pipeout(pipe);

	if (!usb_pipecontrol(pipe) && dev->state < USB_STATE_CONFIGURED)
		return -ENODEV;

	/* FIXME there should be a sharable lock protecting us against
	 * config/altsetting changes and disconnects, kicking in here.
	 * (here == before maxpacket, and eventually endpoint type,
	 * checks get made.)
	 */

	max = usb_maxpacket(dev, pipe, is_out);
	if (max <= 0) {
		dev_dbg(&dev->dev,
			"bogus endpoint ep%d%s in %s (bad maxpacket %d)\n",
			usb_pipeendpoint(pipe), is_out ? "out" : "in",
			__FUNCTION__, max);
		return -EMSGSIZE;
	}

	/* periodic transfers limit size per frame/uframe,
	 * but drivers only control those sizes for ISO.
	 * while we‘re checking, initialize return status.
	 */
	if (temp == PIPE_ISOCHRONOUS) {
		int	n, len;

		/* "high bandwidth" mode, 1-3 packets/uframe? */
		if (dev->speed == USB_SPEED_HIGH) {
			int	mult = 1 + ((max >> 11) & 0x03);
			max &= 0x07ff;
			max *= mult;
		}

		if (urb->number_of_packets <= 0)		    
			return -EINVAL;
		for (n = 0; n < urb->number_of_packets; n++) {
			len = urb->iso_frame_desc[n].length;
			if (len < 0 || len > max) 
				return -EMSGSIZE;
			urb->iso_frame_desc[n].status = -EXDEV;
			urb->iso_frame_desc[n].actual_length = 0;
		}
	}

	/* the I/O buffer must be mapped/unmapped, except when length=0 */
	if (urb->transfer_buffer_length < 0)
		return -EMSGSIZE;

#ifdef DEBUG
	/* stuff that drivers shouldn‘t do, but which shouldn‘t
	 * cause problems in HCDs if they get it wrong.
	 */
	{
	unsigned int	orig_flags = urb->transfer_flags;
	unsigned int	allowed;

	/* enforce simple/standard policy */
	allowed = (URB_NO_TRANSFER_DMA_MAP | URB_NO_SETUP_DMA_MAP |
			URB_NO_INTERRUPT);
	switch (temp) {
	case PIPE_BULK:
		if (is_out)
			allowed |= URB_ZERO_PACKET;
		/* FALLTHROUGH */
	case PIPE_CONTROL:
		allowed |= URB_NO_FSBR;	/* only affects UHCI */
		/* FALLTHROUGH */
	default:			/* all non-iso endpoints */
		if (!is_out)
			allowed |= URB_SHORT_NOT_OK;
		break;
	case PIPE_ISOCHRONOUS:
		allowed |= URB_ISO_ASAP;
		break;
	}
	urb->transfer_flags &= allowed;

	/* fail if submitter gave bogus flags */
	if (urb->transfer_flags != orig_flags) {
		err("BOGUS urb flags, %x --> %x",
			orig_flags, urb->transfer_flags);
		return -EINVAL;
	}
	}
#endif
	/*
	 * Force periodic transfer intervals to be legal values that are
	 * a power of two (so HCDs don‘t need to).
	 *
	 * FIXME want bus->{intr,iso}_sched_horizon values here.  Each HC
	 * supports different values... this uses EHCI/UHCI defaults (and
	 * EHCI can use smaller non-default values).
	 */
	switch (temp) {
	case PIPE_ISOCHRONOUS:
	case PIPE_INTERRUPT:
		/* too small? */
		if (urb->interval <= 0)
			return -EINVAL;
		/* too big? */
		switch (dev->speed) {
		case USB_SPEED_HIGH:	/* units are microframes */
			// NOTE usb handles 2^15
			if (urb->interval > (1024 * 8))
				urb->interval = 1024 * 8;
			temp = 1024 * 8;
			break;
		case USB_SPEED_FULL:	/* units are frames/msec */
		case USB_SPEED_LOW:
			if (temp == PIPE_INTERRUPT) {
				if (urb->interval > 255)
					return -EINVAL;
				// NOTE ohci only handles up to 32
				temp = 128;
			} else {
				if (urb->interval > 1024)
					urb->interval = 1024;
				// NOTE usb and ohci handle up to 2^15
				temp = 1024;
			}
			break;
		default:
			return -EINVAL;
		}
		/* power of two? */
		while (temp > urb->interval)
			temp >>= 1;
		urb->interval = temp;
	}

	return usb_hcd_submit_urb(urb, mem_flags);
}

static inline __u16　usb_maxpacket(struct usb_device *udev, int pipe, int is_out)
{
	struct usb_host_endpoint	*ep;
	unsigned			epnum = usb_pipeendpoint(pipe);

	if (is_out) {
		WARN_ON(usb_pipein(pipe));
		ep = udev->ep_out[epnum];
	} else {
		WARN_ON(usb_pipeout(pipe));
		ep = udev->ep_in[epnum];
	}
	if (!ep)
		return 0;

	/* NOTE:  only 0x07ff bits are for packet size... */
	return le16_to_cpu(ep->desc.wMaxPacketSize);
}