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    Subject[PATCH v8 resend 1/6] Extcon (external connector): import Android's switch class and modify.
    Date
    External connector class (extcon) is based on and an extension of
    Android kernel's switch class located at linux/drivers/switch/.

    This patch provides the before-extension switch class moved to the
    location where the extcon will be located (linux/drivers/extcon/) and
    updates to handle class properly.

    The before-extension class, switch class of Android kernel, commits
    imported are:

    switch: switch class and GPIO drivers. (splitted)
    Author: Mike Lockwood <lockwood@android.com>

    switch: Use device_create instead of device_create_drvdata.
    Author: Arve Hjønnevåg <arve@android.com>

    In this patch, upon the commits of Android kernel, we have added:
    - Relocated and renamed for extcon.
    - Comments, module name, and author information are updated
    - Code clean for successing patches
    - Bugfix: enabling write access without write functions
    - Class/device/sysfs create/remove handling
    - Added comments about uevents
    - Format changes for extcon_dev_register() to have a parent dev.

    Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
    Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
    Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

    --
    Changes from v7
    - Compiler error fixed when it is compiled as a module.
    - Removed out-of-date Kconfig entry

    Changes from v6
    - Updated comment/strings
    - Revised "Android-compatible" mode.
    * Automatically activated if CONFIG_ANDROID && !CONFIG_ANDROID_SWITCH
    * Creates /sys/class/switch/*, which is a copy of /sys/class/extcon/*

    Changes from v5
    - Split the patch
    - Style fixes
    - "Android-compatible" mode is enabled by Kconfig option.

    Changes from v2
    - Updated name_show
    - Sysfs entries are handled by class itself.
    - Updated the method to add/remove devices for the class
    - Comments on uevent send
    - Able to become a module
    - Compatible with Android platform

    Changes from RFC
    - Renamed to extcon (external connector) from multistate switch
    - Added a seperated directory (drivers/extcon)
    - Added kerneldoc comments
    - Removed unused variables from extcon_gpio.c
    - Added ABI Documentation.
    ---
    Documentation/ABI/testing/sysfs-class-extcon | 26 +++
    drivers/Kconfig | 2 +
    drivers/Makefile | 1 +
    drivers/extcon/Kconfig | 17 ++
    drivers/extcon/Makefile | 5 +
    drivers/extcon/extcon_class.c | 236 ++++++++++++++++++++++++++
    include/linux/extcon.h | 82 +++++++++
    7 files changed, 369 insertions(+), 0 deletions(-)
    create mode 100644 Documentation/ABI/testing/sysfs-class-extcon
    create mode 100644 drivers/extcon/Kconfig
    create mode 100644 drivers/extcon/Makefile
    create mode 100644 drivers/extcon/extcon_class.c
    create mode 100644 include/linux/extcon.h

    diff --git a/Documentation/ABI/testing/sysfs-class-extcon b/Documentation/ABI/testing/sysfs-class-extcon
    new file mode 100644
    index 0000000..59a4b1c
    --- /dev/null
    +++ b/Documentation/ABI/testing/sysfs-class-extcon
    @@ -0,0 +1,26 @@
    +What: /sys/class/extcon/.../
    +Date: December 2011
    +Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
    +Description:
    + Provide a place in sysfs for the extcon objects.
    + This allows accessing extcon specific variables.
    + The name of extcon object denoted as ... is the name given
    + with extcon_dev_register.
    +
    +What: /sys/class/extcon/.../name
    +Date: December 2011
    +Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
    +Description:
    + The /sys/class/extcon/.../name shows the name of the extcon
    + object. If the extcon object has an optional callback
    + "show_name" defined, the callback will provide the name with
    + this sysfs node.
    +
    +What: /sys/class/extcon/.../state
    +Date: December 2011
    +Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
    +Description:
    + The /sys/class/extcon/.../state shows the cable attach/detach
    + information of the corresponding extcon object. If the extcon
    + objecct has an optional callback "show_state" defined, the
    + callback will provide the name with this sysfs node.
    diff --git a/drivers/Kconfig b/drivers/Kconfig
    index d236aef..0233ad9 100644
    --- a/drivers/Kconfig
    +++ b/drivers/Kconfig
    @@ -140,4 +140,6 @@ source "drivers/virt/Kconfig"

    source "drivers/devfreq/Kconfig"

    +source "drivers/extcon/Kconfig"
    +
    endmenu
    diff --git a/drivers/Makefile b/drivers/Makefile
    index 95952c8..c41dfa9 100644
    --- a/drivers/Makefile
    +++ b/drivers/Makefile
    @@ -134,3 +134,4 @@ obj-$(CONFIG_VIRT_DRIVERS) += virt/
    obj-$(CONFIG_HYPERV) += hv/

    obj-$(CONFIG_PM_DEVFREQ) += devfreq/
    +obj-$(CONFIG_EXTCON) += extcon/
    diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
    new file mode 100644
    index 0000000..7932e1b
    --- /dev/null
    +++ b/drivers/extcon/Kconfig
    @@ -0,0 +1,17 @@
    +menuconfig EXTCON
    + tristate "External Connector Class (extcon) support"
    + help
    + Say Y here to enable external connector class (extcon) support.
    + This allows monitoring external connectors by userspace
    + via sysfs and uevent and supports external connectors with
    + multiple states; i.e., an extcon that may have multiple
    + cables attached. For example, an external connector of a device
    + may be used to connect an HDMI cable and a AC adaptor, and to
    + host USB ports. Many of 30-pin connectors including PDMI are
    + also good examples.
    +
    +if EXTCON
    +
    +comment "Extcon Device Drivers"
    +
    +endif # MULTISTATE_SWITCH
    diff --git a/drivers/extcon/Makefile b/drivers/extcon/Makefile
    new file mode 100644
    index 0000000..6bc6921
    --- /dev/null
    +++ b/drivers/extcon/Makefile
    @@ -0,0 +1,5 @@
    +#
    +# Makefile for external connector class (extcon) devices
    +#
    +
    +obj-$(CONFIG_EXTCON) += extcon_class.o
    diff --git a/drivers/extcon/extcon_class.c b/drivers/extcon/extcon_class.c
    new file mode 100644
    index 0000000..3c46368
    --- /dev/null
    +++ b/drivers/extcon/extcon_class.c
    @@ -0,0 +1,236 @@
    +/*
    + * drivers/extcon/extcon_class.c
    + *
    + * External connector (extcon) class driver
    + *
    + * Copyright (C) 2012 Samsung Electronics
    + * Author: Donggeun Kim <dg77.kim@samsung.com>
    + * Author: MyungJoo Ham <myungjoo.ham@samsung.com>
    + *
    + * based on android/drivers/switch/switch_class.c
    + * Copyright (C) 2008 Google, Inc.
    + * Author: Mike Lockwood <lockwood@android.com>
    + *
    + * This software is licensed under the terms of the GNU General Public
    + * License version 2, as published by the Free Software Foundation, and
    + * may be copied, distributed, and modified under those terms.
    + *
    + * This program is distributed in the hope that it will be useful,
    + * but WITHOUT ANY WARRANTY; without even the implied warranty of
    + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    + * GNU General Public License for more details.
    + *
    +*/
    +
    +#include <linux/module.h>
    +#include <linux/types.h>
    +#include <linux/init.h>
    +#include <linux/device.h>
    +#include <linux/fs.h>
    +#include <linux/err.h>
    +#include <linux/extcon.h>
    +#include <linux/slab.h>
    +
    +struct class *extcon_class;
    +#if defined(CONFIG_ANDROID) && !defined(CONFIG_ANDROID_SWITCH)
    +static struct class_compat *switch_class;
    +#endif /* CONFIG_ANDROID && !defined(CONFIG_ANDROID_SWITCH) */
    +
    +static ssize_t state_show(struct device *dev, struct device_attribute *attr,
    + char *buf)
    +{
    + struct extcon_dev *edev = (struct extcon_dev *) dev_get_drvdata(dev);
    +
    + if (edev->print_state) {
    + int ret = edev->print_state(edev, buf);
    +
    + if (ret >= 0)
    + return ret;
    + /* Use default if failed */
    + }
    + return sprintf(buf, "%u\n", edev->state);
    +}
    +
    +static ssize_t name_show(struct device *dev, struct device_attribute *attr,
    + char *buf)
    +{
    + struct extcon_dev *edev = (struct extcon_dev *) dev_get_drvdata(dev);
    +
    + /* Optional callback given by the user */
    + if (edev->print_name) {
    + int ret = edev->print_name(edev, buf);
    + if (ret >= 0)
    + return ret;
    + }
    +
    + return sprintf(buf, "%s\n", dev_name(edev->dev));
    +}
    +
    +/**
    + * extcon_set_state() - Set the cable attach states of the extcon device.
    + * @edev: the extcon device
    + * @state: new cable attach status for @edev
    + *
    + * Changing the state sends uevent with environment variable containing
    + * the name of extcon device (envp[0]) and the state output (envp[1]).
    + * Tizen uses this format for extcon device to get events from ports.
    + * Android uses this format as well.
    + */
    +void extcon_set_state(struct extcon_dev *edev, u32 state)
    +{
    + char name_buf[120];
    + char state_buf[120];
    + char *prop_buf;
    + char *envp[3];
    + int env_offset = 0;
    + int length;
    +
    + if (edev->state != state) {
    + edev->state = state;
    +
    + prop_buf = (char *)get_zeroed_page(GFP_KERNEL);
    + if (prop_buf) {
    + length = name_show(edev->dev, NULL, prop_buf);
    + if (length > 0) {
    + if (prop_buf[length - 1] == '\n')
    + prop_buf[length - 1] = 0;
    + snprintf(name_buf, sizeof(name_buf),
    + "NAME=%s", prop_buf);
    + envp[env_offset++] = name_buf;
    + }
    + length = state_show(edev->dev, NULL, prop_buf);
    + if (length > 0) {
    + if (prop_buf[length - 1] == '\n')
    + prop_buf[length - 1] = 0;
    + snprintf(state_buf, sizeof(state_buf),
    + "STATE=%s", prop_buf);
    + envp[env_offset++] = state_buf;
    + }
    + envp[env_offset] = NULL;
    + kobject_uevent_env(&edev->dev->kobj, KOBJ_CHANGE, envp);
    + free_page((unsigned long)prop_buf);
    + } else {
    + dev_err(edev->dev, "out of memory in extcon_set_state\n");
    + kobject_uevent(&edev->dev->kobj, KOBJ_CHANGE);
    + }
    + }
    +}
    +EXPORT_SYMBOL_GPL(extcon_set_state);
    +
    +static struct device_attribute extcon_attrs[] = {
    + __ATTR_RO(state),
    + __ATTR_RO(name),
    +};
    +
    +static int create_extcon_class(void)
    +{
    + if (!extcon_class) {
    + extcon_class = class_create(THIS_MODULE, "extcon");
    + if (IS_ERR(extcon_class))
    + return PTR_ERR(extcon_class);
    + extcon_class->dev_attrs = extcon_attrs;
    +
    +#if defined(CONFIG_ANDROID) && !defined(CONFIG_ANDROID_SWITCH)
    + switch_class = class_compat_register("switch");
    + if (WARN(!switch_class, "cannot allocate"))
    + return -ENOMEM;
    +#endif /* CONFIG_ANDROID && !defined(CONFIG_ANDROID_SWITCH) */
    + }
    +
    + return 0;
    +}
    +
    +static void extcon_cleanup(struct extcon_dev *edev, bool skip)
    +{
    + if (!skip && get_device(edev->dev)) {
    + device_unregister(edev->dev);
    + put_device(edev->dev);
    + }
    +
    + kfree(edev->dev);
    +}
    +
    +static void extcon_dev_release(struct device *dev)
    +{
    + struct extcon_dev *edev = (struct extcon_dev *) dev_get_drvdata(dev);
    +
    + extcon_cleanup(edev, true);
    +}
    +
    +/**
    + * extcon_dev_register() - Register a new extcon device
    + * @edev : the new extcon device (should be allocated before calling)
    + * @dev : the parent device for this extcon device.
    + *
    + * Among the members of edev struct, please set the "user initializing data"
    + * in any case and set the "optional callbacks" if required. However, please
    + * do not set the values of "internal data", which are initialized by
    + * this function.
    + */
    +int extcon_dev_register(struct extcon_dev *edev, struct device *dev)
    +{
    + int ret;
    +
    + if (!extcon_class) {
    + ret = create_extcon_class();
    + if (ret < 0)
    + return ret;
    + }
    +
    + edev->dev = kzalloc(sizeof(struct device), GFP_KERNEL);
    + edev->dev->parent = dev;
    + edev->dev->class = extcon_class;
    + edev->dev->release = extcon_dev_release;
    +
    + dev_set_name(edev->dev, edev->name ? edev->name : dev_name(dev));
    + ret = device_register(edev->dev);
    + if (ret) {
    + put_device(edev->dev);
    + goto err_dev;
    + }
    +#if defined(CONFIG_ANDROID) && !defined(CONFIG_ANDROID_SWITCH)
    + if (switch_class)
    + ret = class_compat_create_link(switch_class, edev->dev,
    + dev);
    +#endif /* CONFIG_ANDROID && !defined(CONFIG_ANDROID_SWITCH) */
    +
    + dev_set_drvdata(edev->dev, edev);
    + edev->state = 0;
    + return 0;
    +
    +err_dev:
    + kfree(edev->dev);
    + return ret;
    +}
    +EXPORT_SYMBOL_GPL(extcon_dev_register);
    +
    +/**
    + * extcon_dev_unregister() - Unregister the extcon device.
    + * @edev: the extcon device instance to be unregitered.
    + *
    + * Note that this does not call kfree(edev) because edev was not allocated
    + * by this class.
    + */
    +void extcon_dev_unregister(struct extcon_dev *edev)
    +{
    + extcon_cleanup(edev, false);
    +}
    +EXPORT_SYMBOL_GPL(extcon_dev_unregister);
    +
    +static int __init extcon_class_init(void)
    +{
    + return create_extcon_class();
    +}
    +module_init(extcon_class_init);
    +
    +static void __exit extcon_class_exit(void)
    +{
    + class_destroy(extcon_class);
    +}
    +module_exit(extcon_class_exit);
    +
    +MODULE_AUTHOR("Mike Lockwood <lockwood@android.com>");
    +MODULE_AUTHOR("Donggeun Kim <dg77.kim@samsung.com>");
    +MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
    +MODULE_DESCRIPTION("External connector (extcon) class driver");
    +MODULE_LICENSE("GPL");
    diff --git a/include/linux/extcon.h b/include/linux/extcon.h
    new file mode 100644
    index 0000000..9cb3aaa
    --- /dev/null
    +++ b/include/linux/extcon.h
    @@ -0,0 +1,82 @@
    +/*
    + * External connector (extcon) class driver
    + *
    + * Copyright (C) 2012 Samsung Electronics
    + * Author: Donggeun Kim <dg77.kim@samsung.com>
    + * Author: MyungJoo Ham <myungjoo.ham@samsung.com>
    + *
    + * based on switch class driver
    + * Copyright (C) 2008 Google, Inc.
    + * Author: Mike Lockwood <lockwood@android.com>
    + *
    + * This software is licensed under the terms of the GNU General Public
    + * License version 2, as published by the Free Software Foundation, and
    + * may be copied, distributed, and modified under those terms.
    + *
    + * This program is distributed in the hope that it will be useful,
    + * but WITHOUT ANY WARRANTY; without even the implied warranty of
    + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    + * GNU General Public License for more details.
    + *
    +*/
    +
    +#ifndef __LINUX_EXTCON_H__
    +#define __LINUX_EXTCON_H__
    +
    +/**
    + * struct extcon_dev - An extcon device represents one external connector.
    + * @name The name of this extcon device. Parent device name is used
    + * if NULL.
    + * @print_name An optional callback to override the method to print the
    + * name of the extcon device.
    + * @print_state An optional callback to override the method to print the
    + * status of the extcon device.
    + * @dev Device of this extcon. Do not provide at register-time.
    + * @state Attach/detach state of this extcon. Do not provide at
    + * register-time
    + *
    + * In most cases, users only need to provide "User initializing data" of
    + * this struct when registering an extcon. In some exceptional cases,
    + * optional callbacks may be needed. However, the values in "internal data"
    + * are overwritten by register function.
    + */
    +struct extcon_dev {
    + /* --- Optional user initializing data --- */
    + const char *name;
    +
    + /* --- Optional callbacks to override class functions --- */
    + ssize_t (*print_name)(struct extcon_dev *edev, char *buf);
    + ssize_t (*print_state)(struct extcon_dev *edev, char *buf);
    +
    + /* --- Internal data. Please do not set. --- */
    + struct device *dev;
    + u32 state;
    +};
    +
    +#if IS_ENABLED(CONFIG_EXTCON)
    +extern int extcon_dev_register(struct extcon_dev *edev, struct device *dev);
    +extern void extcon_dev_unregister(struct extcon_dev *edev);
    +
    +static inline u32 extcon_get_state(struct extcon_dev *edev)
    +{
    + return edev->state;
    +}
    +
    +extern void extcon_set_state(struct extcon_dev *edev, u32 state);
    +#else /* CONFIG_EXTCON */
    +static inline int extcon_dev_register(struct extcon_dev *edev,
    + struct device *dev)
    +{
    + return 0;
    +}
    +
    +static inline void extcon_dev_unregister(struct extcon_dev *edev) { }
    +
    +static inline u32 extcon_get_state(struct extcon_dev *edev)
    +{
    + return 0;
    +}
    +
    +static inline void extcon_set_state(struct extcon_dev *edev, u32 state) { }
    +#endif /* CONFIG_EXTCON */
    +#endif /* __LINUX_EXTCON_H__ */
    --
    1.7.4.1
    --
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