Re: [PATCH v4 3/7] usb: mux: add common code for Intel dual role port mux

[Chanwoo Choi]

Hi Lu,

To handle extcon (external connector), I implemented the unique id
for each external connector on patch[1] instead of using the ambiguous string type. 
[1] 2a9de9c0f08d6 (extcon: Use the unique id for external connector instead of string)

So I recommend that you should use the unique id (ex. EXTCON_USB, EXTCON_USB_HOST)
with extcon_register_notifier(), extcon_get_cable_state_() and extcon_set_cable_state_().

extcon_register_interest() is deprecated-> extcon_register_notifier()
extcon_get_cable_state() is deprecated -> extcon_get_cable_state_()
extcon_set_cable_state() is deprecated -> extcon_set_cable_state_()


You can refer to usage for new function with unique id on patch[2]
[2] 5960387a2fb83 (usb: dwc3: omap: Replace deprecated API of extcon)

I'm sorry for late reply. I add the some comment on below.


On 2016ë 03ì 17ì 14:46, Lu Baolu wrote:
> Several Intel PCHs and SOCs have an internal mux that is used to
> share one USB port between device controller and host controller.
> 
> A usb port mux could be abstracted as the following elements:
> 1) mux state: HOST or PERIPHERAL;
> 2) an extcon cable which triggers the change of mux state between
>    HOST and PERIPHERAL;
> 3) The required action to do the real port switch.
> 
> This patch adds the common code to handle usb port mux. With this
> common code, the individual mux driver, which always is platform
> dependent, could focus on the real operation of mux switch.
> 
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> Reviewed-by: Felipe Balbi <balbi@xxxxxxxxxx>
> ---
>  Documentation/ABI/testing/sysfs-bus-platform |  15 +++
>  MAINTAINERS                                  |   7 ++
>  drivers/usb/Kconfig                          |   2 +
>  drivers/usb/Makefile                         |   1 +
>  drivers/usb/mux/Kconfig                      |  12 ++
>  drivers/usb/mux/Makefile                     |   4 +
>  drivers/usb/mux/intel-mux.c                  | 180 +++++++++++++++++++++++++++
>  include/linux/usb/intel-mux.h                |  43 +++++++
>  8 files changed, 264 insertions(+)
>  create mode 100644 drivers/usb/mux/Kconfig
>  create mode 100644 drivers/usb/mux/Makefile
>  create mode 100644 drivers/usb/mux/intel-mux.c
>  create mode 100644 include/linux/usb/intel-mux.h
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-platform b/Documentation/ABI/testing/sysfs-bus-platform
> index 5172a61..23bf76e 100644
> --- a/Documentation/ABI/testing/sysfs-bus-platform
> +++ b/Documentation/ABI/testing/sysfs-bus-platform
> @@ -18,3 +18,18 @@ Description:
>  		devices to opt-out of driver binding using a driver_override
>  		name such as "none".  Only a single driver may be specified in
>  		the override, there is no support for parsing delimiters.
> +
> +What:		/sys/bus/platform/devices/.../port_mux
> +Date:		Febuary 2016
> +Contact:	Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> +Description:
> +		In some platforms, a single USB port is shared between a USB host
> +		controller and a device controller. A USB mux driver is needed to
> +		handle the port mux. port_mux attribute shows and stores the mux
> +		state.
> +		For read:
> +		'peripheral' - mux switched to PERIPHERAL controller;
> +		'host'       - mux switched to HOST controller.
> +		For write:
> +		'peripheral' - mux will be switched to PERIPHERAL controller;
> +		'host'       - mux will be switched to HOST controller.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index da3e4d8..0dbee11 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -11399,6 +11399,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git
>  S:	Maintained
>  F:	drivers/usb/phy/
>  
> +USB PORT MUX DRIVER
> +M:	Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> +L:	linux-usb@xxxxxxxxxxxxxxx
> +S:	Supported
> +F:	include/linux/usb/intel-mux.h
> +F:	drivers/usb/mux/intel-mux.c
> +
>  USB PRINTER DRIVER (usblp)
>  M:	Pete Zaitcev <zaitcev@xxxxxxxxxx>
>  L:	linux-usb@xxxxxxxxxxxxxxx
> diff --git a/drivers/usb/Kconfig b/drivers/usb/Kconfig
> index 8ed451d..dbd6620 100644
> --- a/drivers/usb/Kconfig
> +++ b/drivers/usb/Kconfig
> @@ -149,6 +149,8 @@ endif # USB
>  
>  source "drivers/usb/phy/Kconfig"
>  
> +source "drivers/usb/mux/Kconfig"
> +
>  source "drivers/usb/gadget/Kconfig"
>  
>  config USB_LED_TRIG
> diff --git a/drivers/usb/Makefile b/drivers/usb/Makefile
> index d5c57f1..6433f0c 100644
> --- a/drivers/usb/Makefile
> +++ b/drivers/usb/Makefile
> @@ -6,6 +6,7 @@
>  
>  obj-$(CONFIG_USB)		+= core/
>  obj-$(CONFIG_USB_SUPPORT)	+= phy/
> +obj-$(CONFIG_USB_SUPPORT)	+= mux/
>  
>  obj-$(CONFIG_USB_DWC3)		+= dwc3/
>  obj-$(CONFIG_USB_DWC2)		+= dwc2/
> diff --git a/drivers/usb/mux/Kconfig b/drivers/usb/mux/Kconfig
> new file mode 100644
> index 0000000..62e2cc3
> --- /dev/null
> +++ b/drivers/usb/mux/Kconfig
> @@ -0,0 +1,12 @@
> +#
> +# USB port mux driver configuration
> +#
> +menu "USB Port MUX drivers"
> +config INTEL_USB_MUX
> +	select EXTCON
> +	def_bool n
> +	help
> +	  Common code for all Intel dual role port mux drivers. All Intel
> +	  usb port mux drivers should select it.
> +
> +endmenu
> diff --git a/drivers/usb/mux/Makefile b/drivers/usb/mux/Makefile
> new file mode 100644
> index 0000000..84f0ae8
> --- /dev/null
> +++ b/drivers/usb/mux/Makefile
> @@ -0,0 +1,4 @@
> +#
> +# Makefile for USB port mux drivers
> +#
> +obj-$(CONFIG_INTEL_USB_MUX)		+= intel-mux.o
> diff --git a/drivers/usb/mux/intel-mux.c b/drivers/usb/mux/intel-mux.c
> new file mode 100644
> index 0000000..bb7b192
> --- /dev/null
> +++ b/drivers/usb/mux/intel-mux.c
> @@ -0,0 +1,180 @@
> +/**
> + * intel_mux.c - USB Port Mux support
> + *
> + * Copyright (C) 2016 Intel Corporation
> + *
> + * Author: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +#include <linux/slab.h>
> +#include <linux/notifier.h>
> +#include <linux/extcon.h>
> +#include <linux/err.h>
> +
> +struct intel_usb_mux {
> +	struct device	*dev;
> +	char		*cable_name;
> +	int		(*cable_set_cb)(struct device *dev);
> +	int		(*cable_unset_cb)(struct device *dev);
> +
> +	struct notifier_block		nb;
> +	struct extcon_specific_cable_nb	obj;
> +
> +	/*
> +	 * The state of the mux.
> +	 * 0, 1 - mux switch state
> +	 * -1   - uninitialized state
> +	 */
> +	int				mux_state;
> +
> +	 /* lock for mux_state */
> +	struct mutex			mux_mutex;
> +};
> +
> +static int usb_mux_change_state(struct intel_usb_mux *mux, int state)
> +{
> +	int ret;
> +	struct device *dev = mux->dev;
> +
> +	dev_WARN_ONCE(dev,
> +		      !mutex_is_locked(&mux->mux_mutex),
> +		      "mutex is unlocked\n");
> +
> +	mux->mux_state = state;
> +
> +	if (mux->mux_state)
> +		ret = mux->cable_set_cb(dev);
> +	else
> +		ret = mux->cable_unset_cb(dev);
> +
> +	return ret;
> +}
> +
> +static int usb_mux_notifier(struct notifier_block *nb,
> +			    unsigned long event, void *ptr)
> +{
> +	struct intel_usb_mux *mux;
> +	int state;
> +	int ret = NOTIFY_DONE;
> +
> +	mux = container_of(nb, struct intel_usb_mux, nb);
> +
> +	state = extcon_get_cable_state(mux->obj.edev,
> +				       mux->cable_name);

Use the extcon_get_cable_stet_().

> +
> +	if (mux->mux_state == -1 || mux->mux_state != state) {
> +		mutex_lock(&mux->mux_mutex);
> +		ret = usb_mux_change_state(mux, state);
> +		mutex_unlock(&mux->mux_mutex);
> +	}
> +
> +	return ret;
> +}
> +
> +static ssize_t port_mux_show(struct device *dev,
> +			     struct device_attribute *attr, char *buf)
> +{
> +	struct intel_usb_mux *mux = dev_get_drvdata(dev);
> +
> +	if (dev_WARN_ONCE(dev, !mux, "mux without data structure\n"))
> +		return 0;
> +
> +	return sprintf(buf, "%s\n", mux->mux_state ? "host" : "peripheral");
> +}
> +
> +static ssize_t port_mux_store(struct device *dev,
> +			      struct device_attribute *attr,
> +			      const char *buf, size_t count)
> +{
> +	struct intel_usb_mux *mux = dev_get_drvdata(dev);
> +	int state;
> +
> +	if (dev_WARN_ONCE(dev, !mux, "mux without data structure\n"))
> +		return -EINVAL;
> +
> +	if (sysfs_streq(buf, "peripheral"))
> +		state = 0;
> +	else if (sysfs_streq(buf, "host"))
> +		state = 1;
> +	else
> +		return -EINVAL;
> +
> +	mutex_lock(&mux->mux_mutex);
> +	usb_mux_change_state(mux, state);
> +	mutex_unlock(&mux->mux_mutex);
> +
> +	return count;
> +}
> +static DEVICE_ATTR_RW(port_mux);
> +
> +int intel_usb_mux_bind_cable(struct device *dev,
> +			     char *extcon_name,
> +			     char *cable_name,
> +			     int (*cable_set_cb)(struct device *dev),
> +			     int (*cable_unset_cb)(struct device *dev))
> +{
> +	int ret;
> +	struct intel_usb_mux *mux;
> +
> +	if (!cable_name)
> +		return -ENODEV;
> +
> +	mux = devm_kzalloc(dev, sizeof(*mux), GFP_KERNEL);
> +	if (!mux)
> +		return -ENOMEM;
> +
> +	mux->dev = dev;
> +	mux->cable_name = kstrdup(cable_name, GFP_KERNEL);
> +	mux->cable_set_cb = cable_set_cb;
> +	mux->cable_unset_cb = cable_unset_cb;
> +	mux->nb.notifier_call = usb_mux_notifier;
> +	mutex_init(&mux->mux_mutex);
> +	mux->mux_state = -1;
> +	dev_set_drvdata(dev, mux);
> +	ret = extcon_register_interest(&mux->obj, extcon_name,
> +				       cable_name, &mux->nb);

Use the extcon_register_notifier()

> +	if (ret) {
> +		kfree(mux->cable_name);
> +		dev_err(dev, "failed to register extcon notifier\n");
> +		return -ENODEV;
> +	}
> +
> +	usb_mux_notifier(&mux->nb, 0, NULL);
> +
> +	/* register the sysfs interface */
> +	ret = device_create_file(dev, &dev_attr_port_mux);
> +	if (ret) {
> +		extcon_unregister_interest(&mux->obj);

Use the extcon_unregister_notifier()

> +		kfree(mux->cable_name);
> +		dev_err(dev, "failed to create sysfs attribute\n");
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(intel_usb_mux_bind_cable);
> +
> +int intel_usb_mux_unbind_cable(struct device *dev)
> +{
> +	struct intel_usb_mux *mux = dev_get_drvdata(dev);
> +
> +	device_remove_file(dev, &dev_attr_port_mux);
> +	extcon_unregister_interest(&mux->obj);

Use the extcon_unregister_notifier()

> +	kfree(mux->cable_name);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(intel_usb_mux_unbind_cable);
> +
> +#ifdef CONFIG_PM_SLEEP
> +void intel_usb_mux_complete(struct device *dev)
> +{
> +	struct intel_usb_mux *mux = dev_get_drvdata(dev);
> +
> +	usb_mux_notifier(&mux->nb, 0, NULL);
> +}
> +EXPORT_SYMBOL_GPL(intel_usb_mux_complete);
> +#endif
> diff --git a/include/linux/usb/intel-mux.h b/include/linux/usb/intel-mux.h
> new file mode 100644
> index 0000000..fd5612d
> --- /dev/null
> +++ b/include/linux/usb/intel-mux.h
> @@ -0,0 +1,43 @@
> +/**
> + * intel_mux.h - USB Port Mux definitions
> + *
> + * Copyright (C) 2016 Intel Corporation
> + *
> + * Author: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#ifndef __LINUX_USB_INTEL_MUX_H
> +#define __LINUX_USB_INTEL_MUX_H
> +
> +#if IS_ENABLED(CONFIG_INTEL_USB_MUX)
> +int intel_usb_mux_bind_cable(struct device *dev, char *extcon_name,
> +			     char *cable_name,
> +			     int (*cable_set_cb)(struct device *dev),
> +			     int (*cable_unset_cb)(struct device *dev));
> +int intel_usb_mux_unbind_cable(struct device *dev);
> +#ifdef CONFIG_PM_SLEEP
> +void intel_usb_mux_complete(struct device *dev);
> +#endif
> +
> +#else
> +static inline int
> +intel_usb_mux_bind_cable(struct device *dev,
> +			 char *extcon_name,
> +			 char *cable_name,
> +			 int (*cable_set_cb)(struct device *dev),
> +			 int (*cable_unset_cb)(struct device *dev))
> +{
> +	return -ENODEV;
> +}
> +
> +static inline int intel_usb_mux_unbind_cable(struct device *dev)
> +{
> +	return 0;
> +}
> +#endif /* CONFIG_INTEL_USB_MUX */
> +
> +#endif /* __LINUX_USB_INTEL_MUX_H */
> 

Best Regards,
Chanwoo Choi