usb.c

linux-2.6.15.6

/*			USB device locking
 *
 * Although locking USB devices should be straightforward, it is
 * complicated by the way the driver-model core works.  When a new USB
 * driver is registered or unregistered, the core will automatically
 * probe or disconnect all matching interfaces on all USB devices while
 * holding the USB subsystem writelock.  There's no good way for us to
 * tell which devices will be used or to lock them beforehand; our only
 * option is to effectively lock all the USB devices.
 *
 * We do that by using a private rw-semaphore, usb_all_devices_rwsem.
 * When locking an individual device you must first acquire the rwsem's
 * readlock.  When a driver is registered or unregistered the writelock
 * must be held.  These actions are encapsulated in the subroutines
 * below, so all a driver needs to do is call usb_lock_device() and
 * usb_unlock_device().
 *
 * Complications arise when several devices are to be locked at the same
 * time.  Only hub-aware drivers that are part of usbcore ever have to
 * do this; nobody else needs to worry about it.  The problem is that
 * usb_lock_device() must not be called to lock a second device since it
 * would acquire the rwsem's readlock reentrantly, leading to deadlock if
 * another thread was waiting for the writelock.  The solution is simple:
 *
 *	When locking more than one device, call usb_lock_device()
 *	to lock the first one.  Lock the others by calling
 *	down(&udev->serialize) directly.
 *
 *	When unlocking multiple devices, use up(&udev->serialize)
 *	to unlock all but the last one.  Unlock the last one by
 *	calling usb_unlock_device().
 *
 *	When locking both a device and its parent, always lock the
 *	the parent first.
 */

/**
 * usb_lock_device - acquire the lock for a usb device structure
 * @udev: device that's being locked
 *
 * Use this routine when you don't hold any other device locks;
 * to acquire nested inner locks call down(&udev->serialize) directly.
 * This is necessary for proper interaction with usb_lock_all_devices().
 */
void usb_lock_device(struct usb_device *udev)
{
	down_read(&usb_all_devices_rwsem);
	down(&udev->serialize);
}

/**
 * usb_trylock_device - attempt to acquire the lock for a usb device structure
 * @udev: device that's being locked
 *
 * Don't use this routine if you already hold a device lock;
 * use down_trylock(&udev->serialize) instead.
 * This is necessary for proper interaction with usb_lock_all_devices().
 *
 * Returns 1 if successful, 0 if contention.
 */
int usb_trylock_device(struct usb_device *udev)
{
	if (!down_read_trylock(&usb_all_devices_rwsem))
		return 0;
	if (down_trylock(&udev->serialize)) {
		up_read(&usb_all_devices_rwsem);
		return 0;
	}
	return 1;
}

/**
 * usb_lock_device_for_reset - cautiously acquire the lock for a
 *	usb device structure
 * @udev: device that's being locked
 * @iface: interface bound to the driver making the request (optional)
 *
 * Attempts to acquire the device lock, but fails if the device is
 * NOTATTACHED or SUSPENDED, or if iface is specified and the interface
 * is neither BINDING nor BOUND.  Rather than sleeping to wait for the
 * lock, the routine polls repeatedly.  This is to prevent deadlock with
 * disconnect; in some drivers (such as usb-storage) the disconnect()
 * or suspend() method will block waiting for a device reset to complete.
 *
 * Returns a negative error code for failure, otherwise 1 or 0 to indicate
 * that the device will or will not have to be unlocked.  (0 can be
 * returned when an interface is given and is BINDING, because in that
 * case the driver already owns the device lock.)
 */
int usb_lock_device_for_reset(struct usb_device *udev,
		struct usb_interface *iface)
{
	unsigned long jiffies_expire = jiffies + HZ;

	if (udev->state == USB_STATE_NOTATTACHED)
		return -ENODEV;
	if (udev->state == USB_STATE_SUSPENDED)
		return -EHOSTUNREACH;
	if (iface) {
		switch (iface->condition) {
		  case USB_INTERFACE_BINDING:
			return 0;
		  case USB_INTERFACE_BOUND:
			break;
		  default:
			return -EINTR;
		}
	}

	while (!usb_trylock_device(udev)) {

		/* If we can't acquire the lock after waiting one second,
		 * we're probably deadlocked */
		if (time_after(jiffies, jiffies_expire))
			return -EBUSY;

		msleep(15);
		if (udev->state == USB_STATE_NOTATTACHED)
			return -ENODEV;
		if (udev->state == USB_STATE_SUSPENDED)
			return -EHOSTUNREACH;
		if (iface && iface->condition != USB_INTERFACE_BOUND)
			return -EINTR;
	}
	return 1;
}

/**
 * usb_unlock_device - release the lock for a usb device structure
 * @udev: device that's being unlocked
 *
 * Use this routine when releasing the only device lock you hold;
 * to release inner nested locks call up(&udev->serialize) directly.
 * This is necessary for proper interaction with usb_lock_all_devices().
 */
void usb_unlock_device(struct usb_device *udev)
{
	up(&udev->serialize);
	up_read(&usb_all_devices_rwsem);
}

/**
 * usb_lock_all_devices - acquire the lock for all usb device structures
 *
 * This is necessary when registering a new driver or probing a bus,
 * since the driver-model core may try to use any usb_device.
 */
void usb_lock_all_devices(void)
{
	down_write(&usb_all_devices_rwsem);
}

/**
 * usb_unlock_all_devices - release the lock for all usb device structures
 */
void usb_unlock_all_devices(void)
{
	up_write(&usb_all_devices_rwsem);
}


static struct usb_device *match_device(struct usb_device *dev,
				       u16 vendor_id, u16 product_id)
{
	struct usb_device *ret_dev = NULL;
	int child;

	dev_dbg(&dev->dev, "check for vendor %04x, product %04x ...\n",
	    le16_to_cpu(dev->descriptor.idVendor),
	    le16_to_cpu(dev->descriptor.idProduct));

	/* see if this device matches */
	if ((vendor_id == le16_to_cpu(dev->descriptor.idVendor)) &&
	    (product_id == le16_to_cpu(dev->descriptor.idProduct))) {
		dev_dbg (&dev->dev, "matched this device!\n");
		ret_dev = usb_get_dev(dev);
		goto exit;
	}

	/* look through all of the children of this device */
	for (child = 0; child < dev->maxchild; ++child) {
		if (dev->children[child]) {
			down(&dev->children[child]->serialize);
			ret_dev = match_device(dev->children[child],
					       vendor_id, product_id);
			up(&dev->children[child]->serialize);
			if (ret_dev)
				goto exit;
		}
	}
exit:
	return ret_dev;
}

/**
 * usb_find_device - find a specific usb device in the system
 * @vendor_id: the vendor id of the device to find
 * @product_id: the product id of the device to find
 *
 * Returns a pointer to a struct usb_device if such a specified usb
 * device is present in the system currently.  The usage count of the
 * device will be incremented if a device is found.  Make sure to call
 * usb_put_dev() when the caller is finished with the device.
 *
 * If a device with the specified vendor and product id is not found,
 * NULL is returned.
 */
struct usb_device *usb_find_device(u16 vendor_id, u16 product_id)
{
	struct list_head *buslist;
	struct usb_bus *bus;
	struct usb_device *dev = NULL;
	
	down(&usb_bus_list_lock);
	for (buslist = usb_bus_list.next;
	     buslist != &usb_bus_list; 
	     buslist = buslist->next) {
		bus = container_of(buslist, struct usb_bus, bus_list);
		if (!bus->root_hub)
			continue;
		usb_lock_device(bus->root_hub);
		dev = match_device(bus->root_hub, vendor_id, product_id);
		usb_unlock_device(bus->root_hub);
		if (dev)
			goto exit;
	}
exit:
	up(&usb_bus_list_lock);
	return dev;
}

/**
 * usb_get_current_frame_number - return current bus frame number
 * @dev: the device whose bus is being queried
 *
 * Returns the current frame number for the USB host controller
 * used with the given USB device.  This can be used when scheduling
 * isochronous requests.
 *
 * Note that different kinds of host controller have different
 * "scheduling horizons".  While one type might support scheduling only
 * 32 frames into the future, others could support scheduling up to
 * 1024 frames into the future.
 */
int usb_get_current_frame_number(struct usb_device *dev)
{
	return dev->bus->op->get_frame_number (dev);
}

/*-------------------------------------------------------------------*/
/*
 * __usb_get_extra_descriptor() finds a descriptor of specific type in the
 * extra field of the interface and endpoint descriptor structs.
 */

int __usb_get_extra_descriptor(char *buffer, unsigned size,
	unsigned char type, void **ptr)
{
	struct usb_descriptor_header *header;

	while (size >= sizeof(struct usb_descriptor_header)) {
		header = (struct usb_descriptor_header *)buffer;

		if (header->bLength < 2) {
			printk(KERN_ERR
				"%s: bogus descriptor, type %d length %d\n",
				usbcore_name,
				header->bDescriptorType, 
				header->bLength);
			return -1;
		}

		if (header->bDescriptorType == type) {
			*ptr = header;
			return 0;
		}

		buffer += header->bLength;
		size -= header->bLength;
	}
	return -1;
}

/**
 * usb_buffer_alloc - allocate dma-consistent buffer for URB_NO_xxx_DMA_MAP
 * @dev: device the buffer will be used with
 * @size: requested buffer size
 * @mem_flags: affect whether allocation may block
 * @dma: used to return DMA address of buffer
 *
 * Return value is either null (indicating no buffer could be allocated), or
 * the cpu-space pointer to a buffer that may be used to perform DMA to the
 * specified device.  Such cpu-space buffers are returned along with the DMA
 * address (through the pointer provided).
 *
 * These buffers are used with URB_NO_xxx_DMA_MAP set in urb->transfer_flags
 * to avoid behaviors like using "DMA bounce buffers", or tying down I/O
 * mapping hardware for long idle periods.  The implementation varies between
 * platforms, depending on details of how DMA will work to this device.
 * Using these buffers also helps prevent cacheline sharing problems on
 * architectures where CPU caches are not DMA-coherent.
 *
 * When the buffer is no longer used, free it with usb_buffer_free().
 */
void *usb_buffer_alloc (
	struct usb_device *dev,
	size_t size,
	gfp_t mem_flags,
	dma_addr_t *dma
)
{
	if (!dev || !dev->bus || !dev->bus->op || !dev->bus->op->buffer_alloc)
		return NULL;
	return dev->bus->op->buffer_alloc (dev->bus, size, mem_flags, dma);
}

/**
 * usb_buffer_free - free memory allocated with usb_buffer_alloc()
 * @dev: device the buffer was used with
 * @size: requested buffer size
 * @addr: CPU address of buffer
 * @dma: DMA address of buffer
 *
 * This reclaims an I/O buffer, letting it be reused.  The memory must have
 * been allocated using usb_buffer_alloc(), and the parameters must match
 * those provided in that allocation request. 
 */
void usb_buffer_free (
	struct usb_device *dev,
	size_t size,
	void *addr,
	dma_addr_t dma
)
{
	if (!dev || !dev->bus || !dev->bus->op || !dev->bus->op->buffer_free)
	    	return;
	dev->bus->op->buffer_free (dev->bus, size, addr, dma);
}

/**
 * usb_buffer_map - create DMA mapping(s) for an urb
 * @urb: urb whose transfer_buffer/setup_packet will be mapped
 *
 * Return value is either null (indicating no buffer could be mapped), or
 * the parameter.  URB_NO_TRANSFER_DMA_MAP and URB_NO_SETUP_DMA_MAP are
 * added to urb->transfer_flags if the operation succeeds.  If the device
 * is connected to this system through a non-DMA controller, this operation
 * always succeeds.
 *
 * This call would normally be used for an urb which is reused, perhaps
 * as the target of a large periodic transfer, with usb_buffer_dmasync()
 * calls to synchronize memory and dma state.
 *
 * Reverse the effect of this call with usb_buffer_unmap().
 */
#if 0
struct urb *usb_buffer_map (struct urb *urb)
{
	struct usb_bus		*bus;
	struct device		*controller;

	if (!urb
			|| !urb->dev
			|| !(bus = urb->dev->bus)
			|| !(controller = bus->controller))
		return NULL;

	if (controller->dma_mask) {
		urb->transfer_dma = dma_map_single (controller,
			urb->transfer_buffer, urb->transfer_buffer_length,
			usb_pipein (urb->pipe)
				? DMA_FROM_DEVICE : DMA_TO_DEVICE);
		if (usb_pipecontrol (urb->pipe))
			urb->setup_dma = dma_map_single (controller,
					urb->setup_packet,
					sizeof (struct usb_ctrlrequest),
					DMA_TO_DEVICE);
	// FIXME generic api broken like pci, can't report errors
	// if (urb->transfer_dma == DMA_ADDR_INVALID) return 0;
	} else
		urb->transfer_dma = ~0;
	urb->transfer_flags |= (URB_NO_TRANSFER_DMA_MAP
				| URB_NO_SETUP_DMA_MAP);
	return urb;
}
#endif  /*  0  */

/* XXX DISABLED, no users currently.  If you wish to re-enable this
 * XXX please determine whether the sync is to transfer ownership of
 * XXX the buffer from device to cpu or vice verse, and thusly use the
 * XXX appropriate _for_{cpu,device}() method.  -DaveM
 */
#if 0

/**
 * usb_buffer_dmasync - synchronize DMA and CPU view of buffer(s)
 * @urb: urb whose transfer_buffer/setup_packet will be synchronized
 */
void usb_buffer_dmasync (struct urb *urb)
{
	struct usb_bus		*bus;
	struct device		*controller;

	if (!urb
			|| !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)
			|| !urb->dev
			|| !(bus = urb->dev->bus)
			|| !(controller = bus->controller))
		return;

	if (controller->dma_mask) {