hub.c

底层驱动开发

	}

	return -EBUSY;
}

static int hub_port_reset(struct usb_hub *hub, int port1,
				struct usb_device *udev, unsigned int delay)
{
	int i, status;

	/* Reset the port */
	for (i = 0; i < PORT_RESET_TRIES; i++) {
		status = set_port_feature(hub->hdev,
				port1, USB_PORT_FEAT_RESET);
		if (status)
			dev_err(hub->intfdev,
					"cannot reset port %d (err = %d)\n",
					port1, status);
		else {
			status = hub_port_wait_reset(hub, port1, udev, delay);
			if (status && status != -ENOTCONN)
				dev_dbg(hub->intfdev,
						"port_wait_reset: err = %d\n",
						status);
		}

		/* return on disconnect or reset */
		switch (status) {
		case 0:
			/* TRSTRCY = 10 ms; plus some extra */
			msleep(10 + 40);
			/* FALL THROUGH */
		case -ENOTCONN:
		case -ENODEV:
			clear_port_feature(hub->hdev,
				port1, USB_PORT_FEAT_C_RESET);
			/* FIXME need disconnect() for NOTATTACHED device */
			usb_set_device_state(udev, status
					? USB_STATE_NOTATTACHED
					: USB_STATE_DEFAULT);
			return status;
		}

		dev_dbg (hub->intfdev,
			"port %d not enabled, trying reset again...\n",
			port1);
		delay = HUB_LONG_RESET_TIME;
	}

	dev_err (hub->intfdev,
		"Cannot enable port %i.  Maybe the USB cable is bad?\n",
		port1);

	return status;
}

/*
 * Disable a port and mark a logical connnect-change event, so that some
 * time later khubd will disconnect() any existing usb_device on the port
 * and will re-enumerate if there actually is a device attached.
 */
static void hub_port_logical_disconnect(struct usb_hub *hub, int port1)
{
	dev_dbg(hub->intfdev, "logical disconnect on port %d\n", port1);
	hub_port_disable(hub, port1, 1);

	/* FIXME let caller ask to power down the port:
	 *  - some devices won't enumerate without a VBUS power cycle
	 *  - SRP saves power that way
	 *  - usb_suspend_device(dev, PMSG_SUSPEND)
	 * That's easy if this hub can switch power per-port, and
	 * khubd reactivates the port later (timer, SRP, etc).
	 * Powerdown must be optional, because of reset/DFU.
	 */

	set_bit(port1, hub->change_bits);
 	kick_khubd(hub);
}


#ifdef	CONFIG_USB_SUSPEND

/*
 * Selective port suspend reduces power; most suspended devices draw
 * less than 500 uA.  It's also used in OTG, along with remote wakeup.
 * All devices below the suspended port are also suspended.
 *
 * Devices leave suspend state when the host wakes them up.  Some devices
 * also support "remote wakeup", where the device can activate the USB
 * tree above them to deliver data, such as a keypress or packet.  In
 * some cases, this wakes the USB host.
 */
static int hub_port_suspend(struct usb_hub *hub, int port1,
		struct usb_device *udev)
{
	int	status;

	// dev_dbg(hub->intfdev, "suspend port %d\n", port1);

	/* enable remote wakeup when appropriate; this lets the device
	 * wake up the upstream hub (including maybe the root hub).
	 *
	 * NOTE:  OTG devices may issue remote wakeup (or SRP) even when
	 * we don't explicitly enable it here.
	 */
	if (udev->actconfig
			// && FIXME (remote wakeup enabled on this bus)
			// ... currently assuming it's always appropriate
			&& (udev->actconfig->desc.bmAttributes
				& USB_CONFIG_ATT_WAKEUP) != 0) {
		status = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
				USB_REQ_SET_FEATURE, USB_RECIP_DEVICE,
				USB_DEVICE_REMOTE_WAKEUP, 0,
				NULL, 0,
				USB_CTRL_SET_TIMEOUT);
		if (status)
			dev_dbg(&udev->dev,
				"won't remote wakeup, status %d\n",
				status);
	}

	/* see 7.1.7.6 */
	status = set_port_feature(hub->hdev, port1, USB_PORT_FEAT_SUSPEND);
	if (status) {
		dev_dbg(hub->intfdev,
			"can't suspend port %d, status %d\n",
			port1, status);
		/* paranoia:  "should not happen" */
		(void) usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
				USB_REQ_CLEAR_FEATURE, USB_RECIP_DEVICE,
				USB_DEVICE_REMOTE_WAKEUP, 0,
				NULL, 0,
				USB_CTRL_SET_TIMEOUT);
	} else {
		/* device has up to 10 msec to fully suspend */
		dev_dbg(&udev->dev, "usb suspend\n");
		usb_set_device_state(udev, USB_STATE_SUSPENDED);
		msleep(10);
	}
	return status;
}

/*
 * Devices on USB hub ports have only one "suspend" state, corresponding
 * to ACPI D2, "may cause the device to lose some context".
 * State transitions include:
 *
 *   - suspend, resume ... when the VBUS power link stays live
 *   - suspend, disconnect ... VBUS lost
 *
 * Once VBUS drop breaks the circuit, the port it's using has to go through
 * normal re-enumeration procedures, starting with enabling VBUS power.
 * Other than re-initializing the hub (plug/unplug, except for root hubs),
 * Linux (2.6) currently has NO mechanisms to initiate that:  no khubd
 * timer, no SRP, no requests through sysfs.
 */
static int __usb_suspend_device (struct usb_device *udev, int port1,
				 pm_message_t state)
{
	int	status;

	/* caller owns the udev device lock */
	if (port1 < 0)
		return port1;

	if (udev->state == USB_STATE_SUSPENDED
			|| udev->state == USB_STATE_NOTATTACHED) {
		return 0;
	}

	/* suspend interface drivers; if this is a hub, it
	 * suspends the child devices
	 */
	if (udev->actconfig) {
		int	i;

		for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) {
			struct usb_interface	*intf;
			struct usb_driver	*driver;

			intf = udev->actconfig->interface[i];
			if (state.event <= intf->dev.power.power_state.event)
				continue;
			if (!intf->dev.driver)
				continue;
			driver = to_usb_driver(intf->dev.driver);

			if (driver->suspend) {
				status = driver->suspend(intf, state);
				if (intf->dev.power.power_state.event != state.event
						|| status)
					dev_err(&intf->dev,
						"suspend %d fail, code %d\n",
						state.event, status);
			}

			/* only drivers with suspend() can ever resume();
			 * and after power loss, even they won't.
			 * bus_rescan_devices() can rebind drivers later.
			 *
			 * FIXME the PM core self-deadlocks when unbinding
			 * drivers during suspend/resume ... everything grabs
			 * dpm_sem (not a spinlock, ugh).  we want to unbind,
			 * since we know every driver's probe/disconnect works
			 * even for drivers that can't suspend.
			 */
			if (!driver->suspend || state.event > PM_EVENT_FREEZE) {
#if 1
				dev_warn(&intf->dev, "resume is unsafe!\n");
#else
				down_write(&usb_bus_type.rwsem);
				device_release_driver(&intf->dev);
				up_write(&usb_bus_type.rwsem);
#endif
			}
		}
	}

	/*
	 * FIXME this needs port power off call paths too, to help force
	 * USB into the "generic" PM model.  At least for devices on
	 * ports that aren't using ganged switching (usually root hubs).
	 *
	 * NOTE: SRP-capable links should adopt more aggressive poweroff
	 * policies (when HNP doesn't apply) once we have mechanisms to
	 * turn power back on!  (Likely not before 2.7...)
	 */
	if (state.event > PM_EVENT_FREEZE) {
		dev_warn(&udev->dev, "no poweroff yet, suspending instead\n");
	}

	/* "global suspend" of the HC-to-USB interface (root hub), or
	 * "selective suspend" of just one hub-device link.
	 */
	if (!udev->parent) {
		struct usb_bus	*bus = udev->bus;
		if (bus && bus->op->hub_suspend) {
			status = bus->op->hub_suspend (bus);
			if (status == 0) {
				dev_dbg(&udev->dev, "usb suspend\n");
				usb_set_device_state(udev,
						USB_STATE_SUSPENDED);
			}
		} else
			status = -EOPNOTSUPP;
	} else
		status = hub_port_suspend(hdev_to_hub(udev->parent), port1,
				udev);

	if (status == 0)
		udev->dev.power.power_state = state;
	return status;
}

/**
 * usb_suspend_device - suspend a usb device
 * @udev: device that's no longer in active use
 * @state: PMSG_SUSPEND to suspend
 * Context: must be able to sleep; device not locked
 *
 * Suspends a USB device that isn't in active use, conserving power.
 * Devices may wake out of a suspend, if anything important happens,
 * using the remote wakeup mechanism.  They may also be taken out of
 * suspend by the host, using usb_resume_device().  It's also routine
 * to disconnect devices while they are suspended.
 *
 * Suspending OTG devices may trigger HNP, if that's been enabled
 * between a pair of dual-role devices.  That will change roles, such
 * as from A-Host to A-Peripheral or from B-Host back to B-Peripheral.
 *
 * Returns 0 on success, else negative errno.
 */
int usb_suspend_device(struct usb_device *udev, pm_message_t state)
{
	int	port1, status;

	port1 = locktree(udev);
	if (port1 < 0)
		return port1;

	status = __usb_suspend_device(udev, port1, state);
	usb_unlock_device(udev);
	return status;
}

/*
 * hardware resume signaling is finished, either because of selective
 * resume (by host) or remote wakeup (by device) ... now see what changed
 * in the tree that's rooted at this device.
 */
static int finish_port_resume(struct usb_device *udev)
{
	int	status;
	u16	devstatus;

	/* caller owns the udev device lock */
	dev_dbg(&udev->dev, "usb resume\n");

	/* usb ch9 identifies four variants of SUSPENDED, based on what
	 * state the device resumes to.  Linux currently won't see the
	 * first two on the host side; they'd be inside hub_port_init()
	 * during many timeouts, but khubd can't suspend until later.
	 */
	usb_set_device_state(udev, udev->actconfig
			? USB_STATE_CONFIGURED
			: USB_STATE_ADDRESS);
	udev->dev.power.power_state = PMSG_ON;

 	/* 10.5.4.5 says be sure devices in the tree are still there.
 	 * For now let's assume the device didn't go crazy on resume,
	 * and device drivers will know about any resume quirks.
	 */
	status = usb_get_status(udev, USB_RECIP_DEVICE, 0, &devstatus);
	if (status < 0)
		dev_dbg(&udev->dev,
			"gone after usb resume? status %d\n",
			status);
	else if (udev->actconfig) {
		unsigned	i;

		le16_to_cpus(&devstatus);
		if (devstatus & (1 << USB_DEVICE_REMOTE_WAKEUP)) {
			status = usb_control_msg(udev,
					usb_sndctrlpipe(udev, 0),
					USB_REQ_CLEAR_FEATURE,
						USB_RECIP_DEVICE,
					USB_DEVICE_REMOTE_WAKEUP, 0,
					NULL, 0,
					USB_CTRL_SET_TIMEOUT);
			if (status) {
				dev_dbg(&udev->dev, "disable remote "
					"wakeup, status %d\n", status);
				status = 0;
			}
		}

		/* resume interface drivers; if this is a hub, it
		 * resumes the child devices
		 */
		for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) {
			struct usb_interface	*intf;
			struct usb_driver	*driver;

			intf = udev->actconfig->interface[i];
			if (intf->dev.power.power_state.event == PM_EVENT_ON)
				continue;
			if (!intf->dev.driver) {
				/* FIXME maybe force to alt 0 */
				continue;
			}
			driver = to_usb_driver(intf->dev.driver);

			/* bus_rescan_devices() may rebind drivers */
			if (!driver->resume)
				continue;

			/* can we do better than just logging errors? */
			status = driver->resume(intf);
			if (intf->dev.power.power_state.event != PM_EVENT_ON
					|| status)
				dev_dbg(&intf->dev,
					"resume fail, state %d code %d\n",
					intf->dev.power.power_state.event, status);
		}
		status = 0;

	} else if (udev->devnum <= 0) {
		dev_dbg(&udev->dev, "bogus resume!\n");
		status = -EINVAL;
	}
	return status;
}

static int
hub_port_resume(struct usb_hub *hub, int port1, struct usb_device *udev)
{
	int	status;

	// dev_dbg(hub->intfdev, "resume port %d\n", port1);

	/* see 7.1.7.7; affects power usage, but not budgeting */
	status = clear_port_feature(hub->hdev,
			port1, USB_PORT_FEAT_SUSPEND);
	if (status) {
		dev_dbg(hub->intfdev,
			"can't resume port %d, status %d\n",
			port1, status);
	} else {
		u16		devstatus;
		u16		portchange;

		/* drive resume for at least 20 msec */
		if (udev)
			dev_dbg(&udev->dev, "RESUME\n");
		msleep(25);

#define LIVE_FLAGS	( USB_PORT_STAT_POWER \
			| USB_PORT_STAT_ENABLE \
			| USB_PORT_STAT_CONNECTION)

		/* Virtual root hubs can trigger on GET_PORT_STATUS to
		 * stop resume signaling.  Then finish the resume
		 * sequence.
		 */
		devstatus = portchange = 0;
		status = hub_port_status(hub, port1,
				&devstatus, &portchange);
		if (status < 0
				|| (devstatus & LIVE_FLAGS) != LIVE_FLAGS
				|| (devstatus & USB_PORT_STAT_SUSPEND) != 0
				) {
			dev_dbg(hub->intfdev,
				"port %d status %04x.%04x after resume, %d\n",
				port1, portchange, devstatus, status);
		} else {
			/* TRSMRCY = 10 msec */
			msleep(10);
			if (udev)
				status = finish_port_resume(udev);
		}
	}
	if (status < 0)
		hub_port_logical_disconnect(hub, port1);

	return status;
}

static int hub_resume (struct usb_interface *intf);

/**
 * usb_resume_device - re-activate a suspended usb device
 * @udev: device to re-activate
 * Context: must be able to sleep; device not locked
 *
 * This will re-activate the suspended device, increasing power usage
 * while letting drivers communicate again with its endpoints.
 * USB resume explicitly guarantees that the power session between
 * the host and the device is the same as it was when the device
 * suspended.
 *
 * Returns 0 on success, else negative errno.
 */
int usb_resume_device(struct usb_device *udev)
{
	int	port1, status;

	port1 = locktree(udev);
	if (port1 < 0)
		return port1;

	/* "global resume" of the HC-to-USB interface (root hub), or
	 * selective resume of one hub-to-device port
	 */
	if (!udev->parent) {
		struct usb_bus	*bus = udev->bus;
		if (bus && bus->op->hub_resume) {
			status = bus->op->hub_resume (bus);
		} else
			status = -EOPNOTSUPP;
		if (status == 0) {
			dev_dbg(&udev->dev, "usb resume\n");
			/* TRSMRCY = 10 msec */
			msleep(10);
			usb_set_device_state (udev, USB_STATE_CONFIGURED);
			udev->dev.power.power_state = PMSG_ON;
			status = hub_resume (udev
					->actconfig->interface[0]);
		}
	} else if (udev->state == USB_STATE_SUSPENDED) {
		// NOTE this fails if parent is also suspended...
		status = hub_port_resume(hdev_to_hub(udev->parent),
				port1, udev);
	} else {
		status = 0;
	}
	if (status < 0) {
		dev_dbg(&udev->dev, "can't resume, status %d\n",
			status);
	}

	usb_unlock_device(udev);