message.c

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		kfree(buf);
	}
	return smallbuf;
}

/*
 * usb_get_device_descriptor - (re)reads the device descriptor (usbcore)
 * @dev: the device whose device descriptor is being updated
 * @size: how much of the descriptor to read
 * Context: !in_interrupt ()
 *
 * Updates the copy of the device descriptor stored in the device structure,
 * which dedicates space for this purpose.
 *
 * Not exported, only for use by the core.  If drivers really want to read
 * the device descriptor directly, they can call usb_get_descriptor() with
 * type = USB_DT_DEVICE and index = 0.
 *
 * 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_device_descriptor(struct usb_device *dev, unsigned int size)
{
	struct usb_device_descriptor *desc;
	int ret;

	if (size > sizeof(*desc))
		return -EINVAL;
	desc = kmalloc(sizeof(*desc), GFP_NOIO);
	if (!desc)
		return -ENOMEM;

	ret = usb_get_descriptor(dev, USB_DT_DEVICE, 0, desc, size);
	if (ret >= 0) 
		memcpy(&dev->descriptor, desc, size);
	kfree(desc);
	return ret;
}

/**
 * usb_get_status - issues a GET_STATUS call
 * @dev: the device whose status is being checked
 * @type: USB_RECIP_*; for device, interface, or endpoint
 * @target: zero (for device), else interface or endpoint number
 * @data: pointer to two bytes of bitmap data
 * Context: !in_interrupt ()
 *
 * Returns device, interface, or endpoint status.  Normally only of
 * interest to see if the device is self powered, or has enabled the
 * remote wakeup facility; or whether a bulk or interrupt endpoint
 * is halted ("stalled").
 *
 * Bits in these status bitmaps are set using the SET_FEATURE request,
 * and cleared using the CLEAR_FEATURE request.  The usb_clear_halt()
 * function should be used to clear halt ("stall") status.
 *
 * 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_status(struct usb_device *dev, int type, int target, void *data)
{
	int ret;
	u16 *status = kmalloc(sizeof(*status), GFP_KERNEL);

	if (!status)
		return -ENOMEM;

	ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
		USB_REQ_GET_STATUS, USB_DIR_IN | type, 0, target, status,
		sizeof(*status), USB_CTRL_GET_TIMEOUT);

	*(u16 *)data = *status;
	kfree(status);
	return ret;
}

/**
 * usb_clear_halt - tells device to clear endpoint halt/stall condition
 * @dev: device whose endpoint is halted
 * @pipe: endpoint "pipe" being cleared
 * Context: !in_interrupt ()
 *
 * This is used to clear halt conditions for bulk and interrupt endpoints,
 * as reported by URB completion status.  Endpoints that are halted are
 * sometimes referred to as being "stalled".  Such endpoints are unable
 * to transmit or receive data until the halt status is cleared.  Any URBs
 * queued for such an endpoint should normally be unlinked by the driver
 * before clearing the halt condition, as described in sections 5.7.5
 * and 5.8.5 of the USB 2.0 spec.
 *
 * Note that control and isochronous endpoints don't halt, although control
 * endpoints report "protocol stall" (for unsupported requests) using the
 * same status code used to report a true stall.
 *
 * This call is synchronous, and may not be used in an interrupt context.
 *
 * Returns zero on success, or else the status code returned by the
 * underlying usb_control_msg() call.
 */
int usb_clear_halt(struct usb_device *dev, int pipe)
{
	int result;
	int endp = usb_pipeendpoint(pipe);
	
	if (usb_pipein (pipe))
		endp |= USB_DIR_IN;

	/* we don't care if it wasn't halted first. in fact some devices
	 * (like some ibmcam model 1 units) seem to expect hosts to make
	 * this request for iso endpoints, which can't halt!
	 */
	result = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
		USB_REQ_CLEAR_FEATURE, USB_RECIP_ENDPOINT,
		USB_ENDPOINT_HALT, endp, NULL, 0,
		USB_CTRL_SET_TIMEOUT);

	/* don't un-halt or force to DATA0 except on success */
	if (result < 0)
		return result;

	/* NOTE:  seems like Microsoft and Apple don't bother verifying
	 * the clear "took", so some devices could lock up if you check...
	 * such as the Hagiwara FlashGate DUAL.  So we won't bother.
	 *
	 * NOTE:  make sure the logic here doesn't diverge much from
	 * the copy in usb-storage, for as long as we need two copies.
	 */

	/* toggle was reset by the clear */
	usb_settoggle(dev, usb_pipeendpoint(pipe), usb_pipeout(pipe), 0);

	return 0;
}

/**
 * usb_disable_endpoint -- Disable an endpoint by address
 * @dev: the device whose endpoint is being disabled
 * @epaddr: the endpoint's address.  Endpoint number for output,
 *	endpoint number + USB_DIR_IN for input
 *
 * Deallocates hcd/hardware state for this endpoint ... and nukes all
 * pending urbs.
 *
 * If the HCD hasn't registered a disable() function, this sets the
 * endpoint's maxpacket size to 0 to prevent further submissions.
 */
void usb_disable_endpoint(struct usb_device *dev, unsigned int epaddr)
{
	unsigned int epnum = epaddr & USB_ENDPOINT_NUMBER_MASK;
	struct usb_host_endpoint *ep;

	if (!dev)
		return;

	if (usb_endpoint_out(epaddr)) {
		ep = dev->ep_out[epnum];
		dev->ep_out[epnum] = NULL;
	} else {
		ep = dev->ep_in[epnum];
		dev->ep_in[epnum] = NULL;
	}
	if (ep) {
		ep->enabled = 0;
		usb_hcd_flush_endpoint(dev, ep);
		usb_hcd_disable_endpoint(dev, ep);
	}
}

/**
 * usb_disable_interface -- Disable all endpoints for an interface
 * @dev: the device whose interface is being disabled
 * @intf: pointer to the interface descriptor
 *
 * Disables all the endpoints for the interface's current altsetting.
 */
void usb_disable_interface(struct usb_device *dev, struct usb_interface *intf)
{
	struct usb_host_interface *alt = intf->cur_altsetting;
	int i;

	for (i = 0; i < alt->desc.bNumEndpoints; ++i) {
		usb_disable_endpoint(dev,
				alt->endpoint[i].desc.bEndpointAddress);
	}
}

/*
 * usb_disable_device - Disable all the endpoints for a USB device
 * @dev: the device whose endpoints are being disabled
 * @skip_ep0: 0 to disable endpoint 0, 1 to skip it.
 *
 * Disables all the device's endpoints, potentially including endpoint 0.
 * Deallocates hcd/hardware state for the endpoints (nuking all or most
 * pending urbs) and usbcore state for the interfaces, so that usbcore
 * must usb_set_configuration() before any interfaces could be used.
 */
void usb_disable_device(struct usb_device *dev, int skip_ep0)
{
	int i;

	dev_dbg(&dev->dev, "%s nuking %s URBs\n", __FUNCTION__,
			skip_ep0 ? "non-ep0" : "all");
	for (i = skip_ep0; i < 16; ++i) {
		usb_disable_endpoint(dev, i);
		usb_disable_endpoint(dev, i + USB_DIR_IN);
	}
	dev->toggle[0] = dev->toggle[1] = 0;

	/* getting rid of interfaces will disconnect
	 * any drivers bound to them (a key side effect)
	 */
	if (dev->actconfig) {
		for (i = 0; i < dev->actconfig->desc.bNumInterfaces; i++) {
			struct usb_interface	*interface;

			/* remove this interface if it has been registered */
			interface = dev->actconfig->interface[i];
			if (!device_is_registered(&interface->dev))
				continue;
			dev_dbg (&dev->dev, "unregistering interface %s\n",
				interface->dev.bus_id);
			usb_remove_sysfs_intf_files(interface);
			device_del (&interface->dev);
		}

		/* Now that the interfaces are unbound, nobody should
		 * try to access them.
		 */
		for (i = 0; i < dev->actconfig->desc.bNumInterfaces; i++) {
			put_device (&dev->actconfig->interface[i]->dev);
			dev->actconfig->interface[i] = NULL;
		}
		dev->actconfig = NULL;
		if (dev->state == USB_STATE_CONFIGURED)
			usb_set_device_state(dev, USB_STATE_ADDRESS);
	}
}


/*
 * usb_enable_endpoint - Enable an endpoint for USB communications
 * @dev: the device whose interface is being enabled
 * @ep: the endpoint
 *
 * Resets the endpoint toggle, and sets dev->ep_{in,out} pointers.
 * For control endpoints, both the input and output sides are handled.
 */
void usb_enable_endpoint(struct usb_device *dev, struct usb_host_endpoint *ep)
{
	int epnum = usb_endpoint_num(&ep->desc);
	int is_out = usb_endpoint_dir_out(&ep->desc);
	int is_control = usb_endpoint_xfer_control(&ep->desc);

	if (is_out || is_control) {
		usb_settoggle(dev, epnum, 1, 0);
		dev->ep_out[epnum] = ep;
	}
	if (!is_out || is_control) {
		usb_settoggle(dev, epnum, 0, 0);
		dev->ep_in[epnum] = ep;
	}
	ep->enabled = 1;
}

/*
 * usb_enable_interface - Enable all the endpoints for an interface
 * @dev: the device whose interface is being enabled
 * @intf: pointer to the interface descriptor
 *
 * Enables all the endpoints for the interface's current altsetting.
 */
static void usb_enable_interface(struct usb_device *dev,
				 struct usb_interface *intf)
{
	struct usb_host_interface *alt = intf->cur_altsetting;
	int i;

	for (i = 0; i < alt->desc.bNumEndpoints; ++i)
		usb_enable_endpoint(dev, &alt->endpoint[i]);
}

/**
 * usb_set_interface - Makes a particular alternate setting be current
 * @dev: the device whose interface is being updated
 * @interface: the interface being updated
 * @alternate: the setting being chosen.
 * Context: !in_interrupt ()
 *
 * This is used to enable data transfers on interfaces that may not
 * be enabled by default.  Not all devices support such configurability.
 * Only the driver bound to an interface may change its setting.
 *
 * Within any given configuration, each interface may have several
 * alternative settings.  These are often used to control levels of
 * bandwidth consumption.  For example, the default setting for a high
 * speed interrupt endpoint may not send more than 64 bytes per microframe,
 * while interrupt transfers of up to 3KBytes per microframe are legal.
 * Also, isochronous endpoints may never be part of an
 * interface's default setting.  To access such bandwidth, alternate
 * interface settings must be made current.
 *
 * Note that in the Linux USB subsystem, bandwidth associated with
 * an endpoint in a given alternate setting is not reserved until an URB
 * is submitted that needs that bandwidth.  Some other operating systems
 * allocate bandwidth early, when a configuration is chosen.
 *
 * This call is synchronous, and may not be used in an interrupt context.
 * Also, drivers must not change altsettings while urbs are scheduled for
 * endpoints in that interface; all such urbs must first be completed
 * (perhaps forced by unlinking).
 *
 * Returns zero on success, or else the status code returned by the
 * underlying usb_control_msg() call.
 */
int usb_set_interface(struct usb_device *dev, int interface, int alternate)
{
	struct usb_interface *iface;
	struct usb_host_interface *alt;
	int ret;
	int manual = 0;

	if (dev->state == USB_STATE_SUSPENDED)
		return -EHOSTUNREACH;

	iface = usb_ifnum_to_if(dev, interface);
	if (!iface) {
		dev_dbg(&dev->dev, "selecting invalid interface %d\n",
			interface);
		return -EINVAL;
	}

	alt = usb_altnum_to_altsetting(iface, alternate);
	if (!alt) {
		warn("selecting invalid altsetting %d", alternate);
		return -EINVAL;
	}

	ret = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
				   USB_REQ_SET_INTERFACE, USB_RECIP_INTERFACE,
				   alternate, interface, NULL, 0, 5000);

	/* 9.4.10 says devices don't need this and are free to STALL the
	 * request if the interface only has one alternate setting.
	 */
	if (ret == -EPIPE && iface->num_altsetting == 1) {
		dev_dbg(&dev->dev,
			"manual set_interface for iface %d, alt %d\n",
			interface, alternate);
		manual = 1;
	} else if (ret < 0)
		return ret;

	/* FIXME drivers shouldn't need to replicate/bugfix the logic here
	 * when they implement async or easily-killable versions of this or
	 * other "should-be-internal" functions (like clear_halt).
	 * should hcd+usbcore postprocess control requests?
	 */

	/* prevent submissions using previous endpoint settings */
	if (iface->cur_altsetting != alt && device_is_registered(&iface->dev))
		usb_remove_sysfs_intf_files(iface);
	usb_disable_interface(dev, iface);

	iface->cur_altsetting = alt;

	/* If the interface only has one altsetting and the device didn't
	 * accept the request, we attempt to carry out the equivalent action
	 * by manually clearing the HALT feature for each endpoint in the
	 * new altsetting.
	 */
	if (manual) {
		int i;

		for (i = 0; i < alt->desc.bNumEndpoints; i++) {
			unsigned int epaddr =
				alt->endpoint[i].desc.bEndpointAddress;
			unsigned int pipe =
	__create_pipe(dev, USB_ENDPOINT_NUMBER_MASK & epaddr)
	| (usb_endpoint_out(epaddr) ? USB_DIR_OUT : USB_DIR_IN);

			usb_clear_halt(dev, pipe);
		}
	}

	/* 9.1.1.5: reset toggles for all endpoints in the new altsetting
	 *
	 * Note:
	 * Despite EP0 is always present in all interfaces/AS, the list of
	 * endpoints from the descriptor does not contain EP0. Due to its
	 * omnipresence one might expect EP0 being considered "affected" by
	 * any SetInterface request and hence assume toggles need to be reset.
	 * However, EP0 toggles are re-synced for every individual transfer
	 * during the SETUP stage - hence EP0 toggles are "don't care" here.
	 * (Likewise, EP0 never "halts" on well designed devices.)
	 */
	usb_enable_interface(dev, iface);
	if (device_is_registered(&iface->dev))
		usb_create_sysfs_intf_files(iface);

	return 0;
}

/**
 * usb_reset_configuration - lightweight device reset
 * @dev: the device whose configuration is being reset
 *
 * This issues a standard SET_CONFIGURATION request to the device using
 * the current configuration.  The effect is to reset most USB-related
 * state in the device, including interface altsettings (reset to zero),
 * endpoint halts (cleared), and data toggle (only for bulk and interrupt
 * endpoints).  Other usbcore state is unchanged, including bindings of
 * usb device drivers to interfaces.
 *
 * Because this affects multiple interfaces, avoid using this with composite
 * (multi-interface) devices.  Instead, the driver for each interface may
 * use usb_set_interface() on the interfaces it claims.  Be careful though;
 * some devices don't support the SET_INTERFACE request, and others won't
 * reset all the interface state (notably data toggles).  Resetting the whole
 * configuration would affect other drivers' interfaces.
 *
 * The caller must own the device lock.