Message-ID: <YKPz7a68duMyXU5x@google.com>
Date:   Tue, 18 May 2021 10:05:49 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Michal Simek <michal.simek@...inx.com>,
        devicetree@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        linux-usb@...r.kernel.org, Peter Chen <peter.chen@...nel.org>,
        linux-kernel@...r.kernel.org, Stephen Boyd <swboyd@...omium.org>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bastien Nocera <hadess@...ess.net>,
        Al Cooper <alcooperx@...il.com>,
        "Alexander A. Klimov" <grandmaster@...klimov.de>,
        Masahiro Yamada <masahiroy@...nel.org>
Subject: Re: [PATCH v10 2/5] USB: misc: Add onboard_usb_hub driver

Hi Alan,

You seemed to have a generally favorable view of this driver,
but I haven't heard from you in a while :)

On v4 expressed a series of suggestions and concerns, which
should be addressed in this version:

https://lore.kernel.org/patchwork/patch/1313000/
https://lore.kernel.org/patchwork/patch/1313001/

Rob acked the DT binding and the of_platform change. Please let me
know if the USB part needs any further changes or if you think this
series is ready to land.

Thanks

Matthias

On Tue, May 11, 2021 at 03:52:20PM -0700, Matthias Kaehlcke wrote:
> The main issue this driver addresses is that a USB hub needs to be
> powered before it can be discovered. For discrete onboard hubs (an
> example for such a hub is the Realtek RTS5411) this is often solved
> by supplying the hub with an 'always-on' regulator, which is kind
> of a hack. Some onboard hubs may require further initialization
> steps, like changing the state of a GPIO or enabling a clock, which
> requires even more hacks. This driver creates a platform device
> representing the hub which performs the necessary initialization.
> Currently it only supports switching on a single regulator, support
> for multiple regulators or other actions can be added as needed.
> Different initialization sequences can be supported based on the
> compatible string.
> 
> Besides performing the initialization the driver can be configured
> to power the hub off during system suspend. This can help to extend
> battery life on battery powered devices which have no requirements
> to keep the hub powered during suspend. The driver can also be
> configured to leave the hub powered when a wakeup capable USB device
> is connected when suspending, and power it off otherwise.
> 
> Technically the driver consists of two drivers, the platform driver
> described above and a very thin USB driver that subclasses the
> generic driver. The purpose of this driver is to provide the platform
> driver with the USB devices corresponding to the hub(s) (a hub
> controller may provide multiple 'logical' hubs, e.g. one to support
> USB 2.0 and another for USB 3.x).
> 
> Note: the driver currently only works with hubs connected directly
> to a root hub, but it could be extended to support other
> configurations if needed.
> 
> Co-developed-by: Ravi Chandra Sadineni <ravisadineni@...omium.org>
> Signed-off-by: Ravi Chandra Sadineni <ravisadineni@...omium.org>
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> ---
> 
> Changes in v10:
> - always use of_is_onboard_usb_hub() stub unless ONBOARD_USB_HUB=y/m
> 
> Changes in v9:
> - none
> 
> Changes in v8:
> - none
> 
> Changes in v7:
> - don't declare stub for of_is_onboard_usb_hub() when
>   CONFIG_COMPILE_TEST is defined
> 
> Changes in v6:
> - use 'companion-hub' to locate the platform device, instead of
>   scanning through the nodes of the parent
> - added ABI documentation for 'always_powered_in_suspend'
> - sysfs_emit() instead of sprintf() in always_powered_in_suspend_show()
> - register sysfs attribute through driver.dev_groups
> - evaluate return value of driver_attach() in _probe()
> - use dev_warn() instead of WARN_ON() in _probe()
> - include 'onboard_hub.h'
> 
> Changes in v5:
> - the platform device is now instantiated from the same DT node
>   as the 'primary' USB hub device
>   - use the USB compatible strings for the platform device
>   - refactored _find_onboard_hub() to search the parents child
>     nodes for a platform device with a matching compatible string
>   - added exported function of_is_onboard_usb_hub() to allow other
>     drivers (like xhci_plat) to check if one of their child DT nodes
>     is a supported hub
> - use late suspend to make sure info about wakeup enabled descendants
>   is updated
> - call driver_attach() for the USB driver in onboard_hub_probe() to
>   make sure the driver is re-attached after the device_release_driver()
>   calls in onboard_hub_remove()
> - renamed sysfs attribute 'power_off_in_suspend' to
>   'always_powered_in_suspend'
> - added sysfs symlinks between platform device and USB devices
> - marked 'onboard_hub_pm_ops' as __maybe_unused
> - removed 'realtek' compatible string which is not needed at this
>   point
> - fix log for regulator_disable() failure
> 
> Changes in v4:
> - updated Kconfig documentation
> - changed the loop in onboard_hub_remove() to release the hub lock
>   before unbinding the USB device and make self deadlock prevention
>   less clunky
> - fixed return value in onboard_hub_usbdev_probe()
> - added entry to MAINTAINERS file
> 
> Changes in v3:
> - updated the commit message
> - updated description in Kconfig
> - remove include of 'core/usb.h'
> - use 'is_powered_on' flag instead of 'has_wakeup_capable_descendants'
> - added 'going_away' flag to struct onboard_hub
>   - don't allow adding new USB devices when the platform device is going away
>   - don't bother with deleting the list item in onboard_hub_remove_usbdev()
>     when the platform device is going away
> - don't assume in onboard_hub_suspend() that all USB hub devices are
>   connected to the same controller
> - removed unnecessary devm_kfree() from onboard_hub_remove_usbdev()
> - fixed error handling in onboard_hub_remove_usbdev()
> - use kstrtobool() instead of strtobool() in power_off_in_suspend_store()
> - unbind USB devices in onboard_hub_remove() to avoid dangling references
>   to the platform device
> - moved put_device() for platform device to _find_onboard_hub()
> - changed return value of onboard_hub_remove_usbdev() to void
> - evaluate return value of onboard_hub_add_usbdev()
> - register 'power_off_in_suspend' as managed device attribute
> - use USB_DEVICE macro instead manual initialization
> - add unwinding to onboard_hub_init()
> - updated MODULE_DESCRIPTION
> - use module_init() instead of device_initcall()
> 
> Changes in v2:
> - check wakeup enabled state of the USB controller instead of
>   using 'wakeup-source' property
> - use sysfs attribute instead of DT property to determine if
>   the hub should be powered off at all during system suspend
> - added missing brace in onboard_hub_suspend()
> - updated commit message
> - use pm_ptr for pm_ops as suggested by Alan
> 
> Changes in v1:
> - renamed the driver to 'onboard_usb_hub'
> - single file for platform and USB driver
> - USB hub devices register with the platform device
>   - the DT includes a phandle of the platform device
> - the platform device now controls when power is turned off
> - the USB driver became a very thin subclass of the generic USB
>   driver
> - enabled autosuspend support
> 
>  .../sysfs-bus-platform-onboard-usb-hub        |   8 +
>  MAINTAINERS                                   |   7 +
>  drivers/usb/misc/Kconfig                      |  17 +
>  drivers/usb/misc/Makefile                     |   1 +
>  drivers/usb/misc/onboard_usb_hub.c            | 415 ++++++++++++++++++
>  include/linux/usb/onboard_hub.h               |  15 +
>  6 files changed, 463 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-platform-onboard-usb-hub
>  create mode 100644 drivers/usb/misc/onboard_usb_hub.c
>  create mode 100644 include/linux/usb/onboard_hub.h
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-platform-onboard-usb-hub b/Documentation/ABI/testing/sysfs-bus-platform-onboard-usb-hub
> new file mode 100644
> index 000000000000..e981d83648e6
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-platform-onboard-usb-hub
> @@ -0,0 +1,8 @@
> +What:		/sys/bus/platform/devices/<dev>/always_powered_in_suspend
> +Date:		March 2021
> +KernelVersion:	5.13
> +Contact:	Matthias Kaehlcke <matthias@...hlcke.net>
> +		linux-usb@...r.kernel.org
> +Description:
> +		(RW) Controls whether the USB hub remains always powered
> +		during system suspend or not.
> \ No newline at end of file
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d92f85ca831d..882ae6e378c5 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -13297,6 +13297,13 @@ S:	Maintained
>  T:	git git://linuxtv.org/media_tree.git
>  F:	drivers/media/i2c/ov9734.c
>  
> +ONBOARD USB HUB DRIVER
> +M:	Matthias Kaehlcke <mka@...omium.org>
> +L:	linux-usb@...r.kernel.org
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/usb/onboard_usb_hub.yaml
> +F:	drivers/usb/misc/onboard_usb_hub.c
> +
>  ONENAND FLASH DRIVER
>  M:	Kyungmin Park <kyungmin.park@...sung.com>
>  L:	linux-mtd@...ts.infradead.org
> diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig
> index 8f1144359012..f534269fbb20 100644
> --- a/drivers/usb/misc/Kconfig
> +++ b/drivers/usb/misc/Kconfig
> @@ -284,3 +284,20 @@ config BRCM_USB_PINMAP
>  	  This option enables support for remapping some USB external
>  	  signals, which are typically on dedicated pins on the chip,
>  	  to any gpio.
> +
> +config USB_ONBOARD_HUB
> +	tristate "Onboard USB hub support"
> +	depends on OF || COMPILE_TEST
> +	help
> +	  Say Y here if you want to support discrete onboard USB hubs that
> +	  don't require an additional control bus for initialization, but
> +	  need some nontrivial form of initialization, such as enabling a
> +	  power regulator. An example for such a hub is the Realtek
> +	  RTS5411.
> +
> +	  The driver can be configured to turn off the power of the hub
> +	  during system suspend. This may reduce power consumption while
> +	  the system is suspended.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called onboard_usb_hub.
> diff --git a/drivers/usb/misc/Makefile b/drivers/usb/misc/Makefile
> index 5f4e598573ab..2c5aec6f1b26 100644
> --- a/drivers/usb/misc/Makefile
> +++ b/drivers/usb/misc/Makefile
> @@ -32,3 +32,4 @@ obj-$(CONFIG_USB_CHAOSKEY)		+= chaoskey.o
>  obj-$(CONFIG_USB_SISUSBVGA)		+= sisusbvga/
>  obj-$(CONFIG_USB_LINK_LAYER_TEST)	+= lvstest.o
>  obj-$(CONFIG_BRCM_USB_PINMAP)		+= brcmstb-usb-pinmap.o
> +obj-$(CONFIG_USB_ONBOARD_HUB)		+= onboard_usb_hub.o
> diff --git a/drivers/usb/misc/onboard_usb_hub.c b/drivers/usb/misc/onboard_usb_hub.c
> new file mode 100644
> index 000000000000..db926699a5ec
> --- /dev/null
> +++ b/drivers/usb/misc/onboard_usb_hub.c
> @@ -0,0 +1,415 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + *  Driver for onboard USB hubs
> + *
> + * Copyright (c) 2020, Google LLC
> + */
> +
> +#include <linux/device.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/suspend.h>
> +#include <linux/sysfs.h>
> +#include <linux/usb.h>
> +#include <linux/usb/hcd.h>
> +#include <linux/usb/onboard_hub.h>
> +
> +static struct usb_device_driver onboard_hub_usbdev_driver;
> +
> +/************************** Platform driver **************************/
> +
> +struct udev_node {
> +	struct usb_device *udev;
> +	struct list_head list;
> +};
> +
> +struct onboard_hub {
> +	struct regulator *vdd;
> +	struct device *dev;
> +	bool always_powered_in_suspend;
> +	bool is_powered_on;
> +	bool going_away;
> +	struct list_head udev_list;
> +	struct mutex lock;
> +};
> +
> +static int onboard_hub_power_on(struct onboard_hub *hub)
> +{
> +	int err;
> +
> +	err = regulator_enable(hub->vdd);
> +	if (err) {
> +		dev_err(hub->dev, "failed to enable regulator: %d\n", err);
> +		return err;
> +	}
> +
> +	hub->is_powered_on = true;
> +
> +	return 0;
> +}
> +
> +static int onboard_hub_power_off(struct onboard_hub *hub)
> +{
> +	int err;
> +
> +	err = regulator_disable(hub->vdd);
> +	if (err) {
> +		dev_err(hub->dev, "failed to disable regulator: %d\n", err);
> +		return err;
> +	}
> +
> +	hub->is_powered_on = false;
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused onboard_hub_suspend(struct device *dev)
> +{
> +	struct onboard_hub *hub = dev_get_drvdata(dev);
> +	struct udev_node *node;
> +	bool power_off;
> +	int rc = 0;
> +
> +	if (hub->always_powered_in_suspend)
> +		return 0;
> +
> +	power_off = true;
> +
> +	mutex_lock(&hub->lock);
> +
> +	list_for_each_entry(node, &hub->udev_list, list) {
> +		if (!device_may_wakeup(node->udev->bus->controller))
> +			continue;
> +
> +		if (usb_wakeup_enabled_descendants(node->udev)) {
> +			power_off = false;
> +			break;
> +		}
> +	}
> +
> +	mutex_unlock(&hub->lock);
> +
> +	if (power_off)
> +		rc = onboard_hub_power_off(hub);
> +
> +	return rc;
> +}
> +
> +static int __maybe_unused onboard_hub_resume(struct device *dev)
> +{
> +	struct onboard_hub *hub = dev_get_drvdata(dev);
> +	int rc = 0;
> +
> +	if (!hub->is_powered_on)
> +		rc = onboard_hub_power_on(hub);
> +
> +	return rc;
> +}
> +
> +static int onboard_hub_add_usbdev(struct onboard_hub *hub, struct usb_device *udev)
> +{
> +	struct udev_node *node;
> +	char link_name[64];
> +	int ret = 0;
> +
> +	mutex_lock(&hub->lock);
> +
> +	if (hub->going_away) {
> +		ret = -EINVAL;
> +		goto unlock;
> +	}
> +
> +	node = devm_kzalloc(hub->dev, sizeof(*node), GFP_KERNEL);
> +	if (!node) {
> +		ret = -ENOMEM;
> +		goto unlock;
> +	}
> +
> +	node->udev = udev;
> +
> +	list_add(&node->list, &hub->udev_list);
> +
> +	snprintf(link_name, sizeof(link_name), "usb_dev.%s", dev_name(&udev->dev));
> +	WARN_ON(sysfs_create_link(&hub->dev->kobj, &udev->dev.kobj, link_name));
> +
> +unlock:
> +	mutex_unlock(&hub->lock);
> +
> +	return ret;
> +}
> +
> +static void onboard_hub_remove_usbdev(struct onboard_hub *hub, struct usb_device *udev)
> +{
> +	struct udev_node *node;
> +	char link_name[64];
> +
> +	snprintf(link_name, sizeof(link_name), "usb_dev.%s", dev_name(&udev->dev));
> +	sysfs_remove_link(&hub->dev->kobj, link_name);
> +
> +	mutex_lock(&hub->lock);
> +
> +	list_for_each_entry(node, &hub->udev_list, list) {
> +		if (node->udev == udev) {
> +			list_del(&node->list);
> +			break;
> +		}
> +	}
> +
> +	mutex_unlock(&hub->lock);
> +}
> +
> +static ssize_t always_powered_in_suspend_show(struct device *dev, struct device_attribute *attr,
> +			   char *buf)
> +{
> +	struct onboard_hub *hub = dev_get_drvdata(dev);
> +
> +	return sysfs_emit(buf, "%d\n", hub->always_powered_in_suspend);
> +}
> +
> +static ssize_t always_powered_in_suspend_store(struct device *dev, struct device_attribute *attr,
> +			    const char *buf, size_t count)
> +{
> +	struct onboard_hub *hub = dev_get_drvdata(dev);
> +	bool val;
> +	int ret;
> +
> +	ret = kstrtobool(buf, &val);
> +	if (ret < 0)
> +		return ret;
> +
> +	hub->always_powered_in_suspend = val;
> +
> +	return count;
> +}
> +static DEVICE_ATTR_RW(always_powered_in_suspend);
> +
> +static struct attribute *onboard_hub_attrs[] = {
> +	&dev_attr_always_powered_in_suspend.attr,
> +	NULL,
> +};
> +ATTRIBUTE_GROUPS(onboard_hub);
> +
> +static int onboard_hub_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct onboard_hub *hub;
> +	int err;
> +
> +	hub = devm_kzalloc(dev, sizeof(*hub), GFP_KERNEL);
> +	if (!hub)
> +		return -ENOMEM;
> +
> +	hub->vdd = devm_regulator_get(dev, "vdd");
> +	if (IS_ERR(hub->vdd))
> +		return PTR_ERR(hub->vdd);
> +
> +	hub->dev = dev;
> +	mutex_init(&hub->lock);
> +	INIT_LIST_HEAD(&hub->udev_list);
> +
> +	dev_set_drvdata(dev, hub);
> +
> +	err = onboard_hub_power_on(hub);
> +	if (err)
> +		return err;
> +
> +	/*
> +	 * The USB driver might have been detached from the USB devices by
> +	 * onboard_hub_remove(), make sure to re-attach it if needed.
> +	 */
> +	err = driver_attach(&onboard_hub_usbdev_driver.drvwrap.driver);
> +	if (err) {
> +		onboard_hub_power_off(hub);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static int onboard_hub_remove(struct platform_device *pdev)
> +{
> +	struct onboard_hub *hub = dev_get_drvdata(&pdev->dev);
> +	struct udev_node *node;
> +	struct usb_device *udev;
> +
> +	hub->going_away = true;
> +
> +	mutex_lock(&hub->lock);
> +
> +	/* unbind the USB devices to avoid dangling references to this device */
> +	while (!list_empty(&hub->udev_list)) {
> +		node = list_first_entry(&hub->udev_list, struct udev_node, list);
> +		udev = node->udev;
> +
> +		/*
> +		 * Unbinding the driver will call onboard_hub_remove_usbdev(),
> +		 * which acquires hub->lock.  We must release the lock first.
> +		 */
> +		get_device(&udev->dev);
> +		mutex_unlock(&hub->lock);
> +		device_release_driver(&udev->dev);
> +		put_device(&udev->dev);
> +		mutex_lock(&hub->lock);
> +	}
> +
> +	mutex_unlock(&hub->lock);
> +
> +	return onboard_hub_power_off(hub);
> +}
> +
> +static const struct of_device_id onboard_hub_match[] = {
> +	{ .compatible = "usbbda,411" },
> +	{ .compatible = "usbbda,5411" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, onboard_hub_match);
> +
> +bool of_is_onboard_usb_hub(const struct device_node *np)
> +{
> +	return !!of_match_node(onboard_hub_match, np);
> +}
> +EXPORT_SYMBOL_GPL(of_is_onboard_usb_hub);
> +
> +static const struct dev_pm_ops __maybe_unused onboard_hub_pm_ops = {
> +	SET_LATE_SYSTEM_SLEEP_PM_OPS(onboard_hub_suspend, onboard_hub_resume)
> +};
> +
> +static struct platform_driver onboard_hub_driver = {
> +	.probe = onboard_hub_probe,
> +	.remove = onboard_hub_remove,
> +
> +	.driver = {
> +		.name = "onboard-usb-hub",
> +		.of_match_table = onboard_hub_match,
> +		.pm = pm_ptr(&onboard_hub_pm_ops),
> +		.dev_groups = onboard_hub_groups,
> +	},
> +};
> +
> +/************************** USB driver **************************/
> +
> +#define VENDOR_ID_REALTEK	0x0bda
> +
> +/*
> + * Returns the onboard_hub platform device that is associated with the USB
> + * device passed as parameter.
> + */
> +static struct onboard_hub *_find_onboard_hub(struct device *dev)
> +{
> +	struct platform_device *pdev;
> +	struct device_node *np;
> +	phandle ph;
> +
> +	pdev = of_find_device_by_node(dev->of_node);
> +	if (!pdev) {
> +		if (of_property_read_u32(dev->of_node, "companion-hub", &ph)) {
> +			dev_err(dev, "failed to read 'companion-hub' property\n");
> +			return ERR_PTR(-EINVAL);
> +		}
> +
> +		np = of_find_node_by_phandle(ph);
> +		if (!np) {
> +			dev_err(dev, "failed to find device node for companion hub\n");
> +			return ERR_PTR(-EINVAL);
> +		}
> +
> +		pdev = of_find_device_by_node(np);
> +		of_node_put(np);
> +
> +		if (!pdev)
> +			return ERR_PTR(-EPROBE_DEFER);
> +	}
> +
> +	put_device(&pdev->dev);
> +
> +	return dev_get_drvdata(&pdev->dev);
> +}
> +
> +static int onboard_hub_usbdev_probe(struct usb_device *udev)
> +{
> +	struct device *dev = &udev->dev;
> +	struct onboard_hub *hub;
> +	int err;
> +
> +	/* ignore supported hubs without device tree node */
> +	if (!dev->of_node)
> +		return -ENODEV;
> +
> +	hub = _find_onboard_hub(dev);
> +	if (IS_ERR(hub))
> +		return PTR_ERR(hub);
> +
> +	dev_set_drvdata(dev, hub);
> +
> +	err = onboard_hub_add_usbdev(hub, udev);
> +	if (err)
> +		return err;
> +
> +	err = sysfs_create_link(&udev->dev.kobj, &hub->dev->kobj, "onboard_hub_dev");
> +	if (err)
> +		dev_warn(&udev->dev, "failed to create symlink to platform device: %d\n", err);
> +
> +	return 0;
> +}
> +
> +static void onboard_hub_usbdev_disconnect(struct usb_device *udev)
> +{
> +	struct onboard_hub *hub = dev_get_drvdata(&udev->dev);
> +
> +	sysfs_remove_link(&udev->dev.kobj, "onboard_hub_dev");
> +
> +	onboard_hub_remove_usbdev(hub, udev);
> +}
> +
> +static const struct usb_device_id onboard_hub_id_table[] = {
> +	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x0411) }, /* RTS5411 USB 3.0 */
> +	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x5411) }, /* RTS5411 USB 2.0 */
> +	{},
> +};
> +
> +MODULE_DEVICE_TABLE(usb, onboard_hub_id_table);
> +
> +static struct usb_device_driver onboard_hub_usbdev_driver = {
> +
> +	.name = "onboard-usb-hub",
> +	.probe = onboard_hub_usbdev_probe,
> +	.disconnect = onboard_hub_usbdev_disconnect,
> +	.generic_subclass = 1,
> +	.supports_autosuspend =	1,
> +	.id_table = onboard_hub_id_table,
> +};
> +
> +/************************** Driver (de)registration **************************/
> +
> +static int __init onboard_hub_init(void)
> +{
> +	int ret;
> +
> +	ret = platform_driver_register(&onboard_hub_driver);
> +	if (ret)
> +		return ret;
> +
> +	ret = usb_register_device_driver(&onboard_hub_usbdev_driver, THIS_MODULE);
> +	if (ret)
> +		platform_driver_unregister(&onboard_hub_driver);
> +
> +	return ret;
> +}
> +module_init(onboard_hub_init);
> +
> +static void __exit onboard_hub_exit(void)
> +{
> +	usb_deregister_device_driver(&onboard_hub_usbdev_driver);
> +	platform_driver_unregister(&onboard_hub_driver);
> +}
> +module_exit(onboard_hub_exit);
> +
> +MODULE_AUTHOR("Matthias Kaehlcke <mka@...omium.org>");
> +MODULE_DESCRIPTION("Driver for discrete onboard USB hubs");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/usb/onboard_hub.h b/include/linux/usb/onboard_hub.h
> new file mode 100644
> index 000000000000..9be52dfae653
> --- /dev/null
> +++ b/include/linux/usb/onboard_hub.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef __LINUX_USB_ONBOARD_HUB_H
> +#define __LINUX_USB_ONBOARD_HUB_H
> +
> +#ifdef CONFIG_USB_ONBOARD_HUB
> +bool of_is_onboard_usb_hub(const struct device_node *np);
> +#else
> +static inline bool of_is_onboard_usb_hub(const struct device_node *np)
> +{
> +	return false;
> +}
> +#endif
> +
> +#endif /* __LINUX_USB_ONBOARD_HUB_H */
> -- 
> 2.31.1.607.g51e8a6a459-goog
> 

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