Linux内核中ideapad-laptop.c文件全解析6

接前一篇文章《Linux内核中ideapad-laptop.c文件全解析5》，地址为：

Linux内核中ideapad-laptop.c文件全解析5_蓝天居士的博客-优快云博客

上一篇详细分析了ideapad_debugfs_init，本篇详细分析ideapad_input_init。

• ideapad_input_init

ideapad_input_init在同文件（drivers/platform/x86/ideapad-laptop.c）中实现，代码如下：

static int ideapad_input_init(struct ideapad_private *priv)
{
	struct input_dev *inputdev;
	int err;

	inputdev = input_allocate_device();
	if (!inputdev)
		return -ENOMEM;

	inputdev->name = "Ideapad extra buttons";
	inputdev->phys = "ideapad/input0";
	inputdev->id.bustype = BUS_HOST;
	inputdev->dev.parent = &priv->platform_device->dev;

	err = sparse_keymap_setup(inputdev, ideapad_keymap, NULL);
	if (err) {
		dev_err(&priv->platform_device->dev,
			"Could not set up input device keymap: %d\n", err);
		goto err_free_dev;
	}

	err = input_register_device(inputdev);
	if (err) {
		dev_err(&priv->platform_device->dev,
			"Could not register input device: %d\n", err);
		goto err_free_dev;
	}

	priv->inputdev = inputdev;

	return 0;

err_free_dev:
	input_free_device(inputdev);

	return err;
}

static void ideapad_input_exit(struct ideapad_private *priv)
{
	input_unregister_device(priv->inputdev);
	priv->inputdev = NULL;
}

input_allocate_device函数在drivers/input/input.c中，代码如下：

/**
 * input_allocate_device - allocate memory for new input device
 *
 * Returns prepared struct input_dev or %NULL.
 *
 * NOTE: Use input_free_device() to free devices that have not been
 * registered; input_unregister_device() should be used for already
 * registered devices.
 */
struct input_dev *input_allocate_device(void)
{
	static atomic_t input_no = ATOMIC_INIT(-1);
	struct input_dev *dev;

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (dev) {
		dev->dev.type = &input_dev_type;
		dev->dev.class = &input_class;
		device_initialize(&dev->dev);
		mutex_init(&dev->mutex);
		spin_lock_init(&dev->event_lock);
		timer_setup(&dev->timer, NULL, 0);
		INIT_LIST_HEAD(&dev->h_list);
		INIT_LIST_HEAD(&dev->node);

		dev_set_name(&dev->dev, "input%lu",
			     (unsigned long)atomic_inc_return(&input_no));

		__module_get(THIS_MODULE);
	}

	return dev;
}
EXPORT_SYMBOL(input_allocate_device);

由input_allocate_device函数，就进入了Linux输入子系统（Linux Input Subsystem）。

以下内容引自input 子系统架构总结_lbmygf的博客-优快云博客

#############################################################################

Linux 的输入子系统不仅支持鼠标、键盘等常规输入设备，而且还支持蜂鸣器、触摸屏等设备。

输入子系统又叫input子系统。其构建非常灵活，只需要调用一些简单的函数，就可以将一个输入设备的功能呈现给应用程序。

#############################################################################
input_allocate_device函数位于核心层，其作用是动态分配一个input_dev结构体实例并初始化。该结构体是一个输入设备结构体，包含了输入设备的一些相关信息，如：设备支持的按键码、设备的名称、设备支持的事件等。函数返回一个指向函数中动态分配的input_dev结构实例的指针。

sparse_keymap_setup函数在drivers/input/sparse-keymap.c中，代码如下：

/**
 * sparse_keymap_setup - set up sparse keymap for an input device
 * @dev: Input device
 * @keymap: Keymap in form of array of &key_entry structures ending
 *	with %KE_END type entry
 * @setup: Function that can be used to adjust keymap entries
 *	depending on device's needs, may be %NULL
 *
 * The function calculates size and allocates copy of the original
 * keymap after which sets up input device event bits appropriately.
 * The allocated copy of the keymap is automatically freed when it
 * is no longer needed.
 */
int sparse_keymap_setup(struct input_dev *dev,
			const struct key_entry *keymap,
			int (*setup)(struct input_dev *, struct key_entry *))
{
	size_t map_size = 1; /* to account for the last KE_END entry */
	const struct key_entry *e;
	struct key_entry *map, *entry;
	int i;
	int error;

	for (e = keymap; e->type != KE_END; e++)
		map_size++;

	map = devm_kmemdup(&dev->dev, keymap, map_size * sizeof(*map),
			   GFP_KERNEL);
	if (!map)
		return -ENOMEM;

	for (i = 0; i < map_size; i++) {
		entry = &map[i];

		if (setup) {
			error = setup(dev, entry);
			if (error)
				return error;
		}

		switch (entry->type) {
		case KE_KEY:
			__set_bit(EV_KEY, dev->evbit);
			__set_bit(entry->keycode, dev->keybit);
			break;

		case KE_SW:
		case KE_VSW:
			__set_bit(EV_SW, dev->evbit);
			__set_bit(entry->sw.code, dev->swbit);
			break;
		}
	}

	if (test_bit(EV_KEY, dev->evbit)) {
		__set_bit(KEY_UNKNOWN, dev->keybit);
		__set_bit(EV_MSC, dev->evbit);
		__set_bit(MSC_SCAN, dev->mscbit);
	}

	dev->keycode = map;
	dev->keycodemax = map_size;
	dev->getkeycode = sparse_keymap_getkeycode;
	dev->setkeycode = sparse_keymap_setkeycode;

	return 0;
}
EXPORT_SYMBOL(sparse_keymap_setup);

如函数说明，sparse_keymap_setup函数建立了输入设备的稀疏键映射。

ideapad_input_init函数中调用sparse_keymap_setup时，第2个参数const struct key_entry *keymap传入的实参是ideapad_keymap。ideapad_keymap数组在同文件（drivers/platform/x86/ideapad-laptop.c）中初始化，如下代码：

static const struct key_entry ideapad_keymap[] = {
	{ KE_KEY,   6, { KEY_SWITCHVIDEOMODE } },
	{ KE_KEY,   7, { KEY_CAMERA } },
	{ KE_KEY,   8, { KEY_MICMUTE } },
	{ KE_KEY,  11, { KEY_F16 } },
	{ KE_KEY,  13, { KEY_WLAN } },
	{ KE_KEY,  16, { KEY_PROG1 } },
	{ KE_KEY,  17, { KEY_PROG2 } },
	{ KE_KEY,  64, { KEY_PROG3 } },
	{ KE_KEY,  65, { KEY_PROG4 } },
	{ KE_KEY,  66, { KEY_TOUCHPAD_OFF } },
	{ KE_KEY,  67, { KEY_TOUCHPAD_ON } },
	{ KE_KEY, 128, { KEY_ESC } },
	{ KE_END },
};

input_register_device函数是input设备注册的接口，在drivers/input/input.c中，代码如下：

/**
 * input_register_device - register device with input core
 * @dev: device to be registered
 *
 * This function registers device with input core. The device must be
 * allocated with input_allocate_device() and all it's capabilities
 * set up before registering.
 * If function fails the device must be freed with input_free_device().
 * Once device has been successfully registered it can be unregistered
 * with input_unregister_device(); input_free_device() should not be
 * called in this case.
 *
 * Note that this function is also used to register managed input devices
 * (ones allocated with devm_input_allocate_device()). Such managed input
 * devices need not be explicitly unregistered or freed, their tear down
 * is controlled by the devres infrastructure. It is also worth noting
 * that tear down of managed input devices is internally a 2-step process:
 * registered managed input device is first unregistered, but stays in
 * memory and can still handle input_event() calls (although events will
 * not be delivered anywhere). The freeing of managed input device will
 * happen later, when devres stack is unwound to the point where device
 * allocation was made.
 */
int input_register_device(struct input_dev *dev)
{
	struct input_devres *devres = NULL;
	struct input_handler *handler;
	unsigned int packet_size;
	const char *path;
	int error;

	if (test_bit(EV_ABS, dev->evbit) && !dev->absinfo) {
		dev_err(&dev->dev,
			"Absolute device without dev->absinfo, refusing to register\n");
		return -EINVAL;
	}

	if (dev->devres_managed) {
		devres = devres_alloc(devm_input_device_unregister,
				      sizeof(*devres), GFP_KERNEL);
		if (!devres)
			return -ENOMEM;

		devres->input = dev;
	}

	/* Every input device generates EV_SYN/SYN_REPORT events. */
	__set_bit(EV_SYN, dev->evbit);

	/* KEY_RESERVED is not supposed to be transmitted to userspace. */
	__clear_bit(KEY_RESERVED, dev->keybit);

	/* Make sure that bitmasks not mentioned in dev->evbit are clean. */
	input_cleanse_bitmasks(dev);

	packet_size = input_estimate_events_per_packet(dev);
	if (dev->hint_events_per_packet < packet_size)
		dev->hint_events_per_packet = packet_size;

	dev->max_vals = dev->hint_events_per_packet + 2;
	dev->vals = kcalloc(dev->max_vals, sizeof(*dev->vals), GFP_KERNEL);
	if (!dev->vals) {
		error = -ENOMEM;
		goto err_devres_free;
	}

	/*
	 * If delay and period are pre-set by the driver, then autorepeating
	 * is handled by the driver itself and we don't do it in input.c.
	 */
	if (!dev->rep[REP_DELAY] && !dev->rep[REP_PERIOD])
		input_enable_softrepeat(dev, 250, 33);

	if (!dev->getkeycode)
		dev->getkeycode = input_default_getkeycode;

	if (!dev->setkeycode)
		dev->setkeycode = input_default_setkeycode;

	if (dev->poller)
		input_dev_poller_finalize(dev->poller);

	error = device_add(&dev->dev);
	if (error)
		goto err_free_vals;

	path = kobject_get_path(&dev->dev.kobj, GFP_KERNEL);
	pr_info("%s as %s\n",
		dev->name ? dev->name : "Unspecified device",
		path ? path : "N/A");
	kfree(path);

	error = mutex_lock_interruptible(&input_mutex);
	if (error)
		goto err_device_del;

	list_add_tail(&dev->node, &input_dev_list);

	list_for_each_entry(handler, &input_handler_list, node)
		input_attach_handler(dev, handler);

	input_wakeup_procfs_readers();

	mutex_unlock(&input_mutex);

	if (dev->devres_managed) {
		dev_dbg(dev->dev.parent, "%s: registering %s with devres.\n",
			__func__, dev_name(&dev->dev));
		devres_add(dev->dev.parent, devres);
	}
	return 0;

err_device_del:
	device_del(&dev->dev);
err_free_vals:
	kfree(dev->vals);
	dev->vals = NULL;
err_devres_free:
	devres_free(devres);
	return error;
}
EXPORT_SYMBOL(input_register_device);

输入子系统部分的代码要完全分析清楚，需要一个系列才可以。由于这并不是我们的重点，所以只是点到为止，把涉及到的接口及代码列在这里，并不深入展开了。

至此，ideapad_input_init函数也就算是分析完了。