Linux内核中ideapad-laptop.c文件全解析9

接前一篇文章《Linux内核中ideapad-laptop.c文件全解析8》，地址为：

Linux内核中ideapad-laptop.c文件全解析8_蓝天居士的博客-CSDN博客

上一回详细分析了ideapad_kbd_bl_init，这一回详细分析ideapad_acpi_notify。

• ideapad_acpi_notify

ideapad_acpi_notify函数在同文件（linux-5.18.8/drivers/platform/x86/ideapad-laptop.c）中实现，源码如下：

static void ideapad_acpi_notify(acpi_handle handle, u32 event, void *data)
{
	struct ideapad_private *priv = data;
	unsigned long vpc1, vpc2, bit;
 
	if (read_ec_data(handle, VPCCMD_R_VPC1, &vpc1))
		return;
 
	if (read_ec_data(handle, VPCCMD_R_VPC2, &vpc2))
		return;
 
	vpc1 = (vpc2 << 8) | vpc1;
 
	for_each_set_bit (bit, &vpc1, 16) {
		switch (bit) {
		case 13:
		case 11:
		case 8:
		case 7:
		case 6:
			ideapad_input_report(priv, bit);
			break;
		case 10:
			/*
			 * This event gets send on a Yoga 300-11IBR when the EC
			 * believes that the device has changed between laptop/
			 * tent/stand/tablet mode. The EC relies on getting
			 * angle info from 2 accelerometers through a special
			 * windows service calling a DSM on the DUAL250E ACPI-
			 * device. Linux does not do this, making the laptop/
			 * tent/stand/tablet mode info unreliable, so we simply
			 * ignore these events.
			 */
			break;
		case 9:
			ideapad_sync_rfk_state(priv);
			break;
		case 5:
			ideapad_sync_touchpad_state(priv);
			break;
		case 4:
			ideapad_backlight_notify_brightness(priv);
			break;
		case 3:
			ideapad_input_novokey(priv);
			break;
		case 2:
			ideapad_backlight_notify_power(priv);
			break;
		case 1:
			/*
			 * Some IdeaPads report event 1 every ~20
			 * seconds while on battery power; some
			 * report this when changing to/from tablet
			 * mode; some report this when the keyboard
			 * backlight has changed.
			 */
			ideapad_kbd_bl_notify(priv);
			break;
		case 0:
			ideapad_check_special_buttons(priv);
			break;
		default:
			dev_info(&priv->platform_device->dev,
				 "Unknown event: %lu\n", bit);
		}
	}
}

函数一上来通过read_ec_data读取ec中的寄存器值（VPCCMD_R_VPC1和VPCCMD_R_VPC2），之后将读到的两个值vpc1和vpc2组合在一起，赋给vpc1（vpc1 = (vpc2 << 8) | vpc1;）。

然后依次遍历vpc1的低16位，略过没有被置位的位，而对于被置位的位进行相应的处理。这里我们重点关注case 1的处理，其中的处理函数为ideapad_kbd_bl_notify(priv)。

这里看一下for_each_set_bit宏定义，在include/linux/find.h中：

#define for_each_set_bit(bit, addr, size) \
	for ((bit) = find_next_bit((addr), (size), 0);		\
	     (bit) < (size);					\
	     (bit) = find_next_bit((addr), (size), (bit) + 1))

find_next_bit在同文件中定义并实现，代码如下：

#ifndef find_next_bit
/**
 * find_next_bit - find the next set bit in a memory region
 * @addr: The address to base the search on
 * @offset: The bitnumber to start searching at
 * @size: The bitmap size in bits
 *
 * Returns the bit number for the next set bit
 * If no bits are set, returns @size.
 */
static inline
unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
			    unsigned long offset)
{
	if (small_const_nbits(size)) {
		unsigned long val;
 
		if (unlikely(offset >= size))
			return size;
 
		val = *addr & GENMASK(size - 1, offset);
		return val ? __ffs(val) : size;
	}
 
	return _find_next_bit(addr, NULL, size, offset, 0UL, 0);
}
#endif

下边还是分析ideapad_kbd_bl_notify函数，其在drivers/platform/x86/ideapad-laptop.c中，代码如下：

static void ideapad_kbd_bl_notify(struct ideapad_private *priv)
{
	int brightness;
 
	if (!priv->kbd_bl.initialized)
		return;
 
	brightness = ideapad_kbd_bl_brightness_get(priv);
	if (brightness < 0)
		return;
 
	if (brightness == priv->kbd_bl.last_brightness)
		return;
 
	priv->kbd_bl.last_brightness = brightness;
 
	led_classdev_notify_brightness_hw_changed(&priv->kbd_bl.led, brightness);
}

如果kbd_bl.initialized为false，即没有被初始化过，则直接返回。根据《Linux内核中ideapad-laptop.c文件全解析7》中的介绍，在ideapad_kbd_bl_init函数中，kbd_bl.initialized已经被设置为了true。

ideapad_kbd_bl_brightness_get函数在同文件中实现，代码如下：

static int ideapad_kbd_bl_brightness_get(struct ideapad_private *priv)
{
	unsigned long hals;
	int err;
 
	err = eval_hals(priv->adev->handle, &hals);
	if (err)
		return err;
 
	return !!test_bit(HALS_KBD_BL_STATE_BIT, &hals);
}

test_bit是一个架构相关函数，其作用是原子地返回addr所指对象的nr位。在这里是返回hals的HALS_KBD_BL_STATE_BIT位，给brightness。

如果本次的brightness值不等于上一次的值，则把本次的值赋给上一次的值last_brightness。

led_classdev_notify_brightness_hw_changed函数视编译选项CONFIG_LEDS_BRIGHTNESS_HW_CHANGED而定。在drivers/platform/x86/ideapad-laptop.c中，如下所示：

#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
void led_classdev_notify_brightness_hw_changed(
	struct led_classdev *led_cdev, unsigned int brightness);
#else
static inline void led_classdev_notify_brightness_hw_changed(
	struct led_classdev *led_cdev, enum led_brightness brightness) { }
#endif

如果没有定义CONFIG_LEDS_BRIGHTNESS_HW_CHANGED，即没有使能此配置选项，则为空函数；如果定义了CONFIG_LEDS_BRIGHTNESS_HW_CHANGED，即使能了此配置选项，则led_classdev_notify_brightness_hw_changed的实现在drivers/leds/led-class.c中，代码如下：

void led_classdev_notify_brightness_hw_changed(struct led_classdev *led_cdev, unsigned int brightness)
{
	if (WARN_ON(!led_cdev->brightness_hw_changed_kn))
		return;
 
	led_cdev->brightness_hw_changed = brightness;
	sysfs_notify_dirent(led_cdev->brightness_hw_changed_kn);
}
EXPORT_SYMBOL_GPL(led_classdev_notify_brightness_hw_changed);

可以看到，必须设置了brightness_hw_changed_kn（struct led_classdev中的成员struct kernfs_node *brightness_hw_changed_kn;）才能往下走。brightness_hw_changed_kn是在哪里赋值的？是在上一篇文章中最后提到的led_classdev_register_ext函数，其中有这样一段：

    if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
		ret = led_add_brightness_hw_changed(led_cdev);
		if (ret) {
			device_unregister(led_cdev->dev);
			led_cdev->dev = NULL;
			mutex_unlock(&led_cdev->led_access);
			return ret;
		}
	}

led_add_brightness_hw_changed函数在drivers/leds/led-class.c中实现，代码如下：

static int led_add_brightness_hw_changed(struct led_classdev *led_cdev)
{
	struct device *dev = led_cdev->dev;
	int ret;
 
	ret = device_create_file(dev, &dev_attr_brightness_hw_changed);
	if (ret) {
		dev_err(dev, "Error creating brightness_hw_changed\n");
		return ret;
	}
 
	led_cdev->brightness_hw_changed_kn =
		sysfs_get_dirent(dev->kobj.sd, "brightness_hw_changed");
	if (!led_cdev->brightness_hw_changed_kn) {
		dev_err(dev, "Error getting brightness_hw_changed kn\n");
		device_remove_file(dev, &dev_attr_brightness_hw_changed);
		return -ENXIO;
	}
 
	return 0;
}

其中，device_create_file函数和Linux内核中ideapad-laptop.c文件全解析3_蓝天居士的博客-CSDN博客中分析的device_add_groups函数都在drivers/base/core.c中实现，代码如下：

/**
 * device_create_file - create sysfs attribute file for device.
 * @dev: device.
 * @attr: device attribute descriptor.
 */
int device_create_file(struct device *dev,
		       const struct device_attribute *attr)
{
	int error = 0;
 
	if (dev) {
		WARN(((attr->attr.mode & S_IWUGO) && !attr->store),
			"Attribute %s: write permission without 'store'\n",
			attr->attr.name);
		WARN(((attr->attr.mode & S_IRUGO) && !attr->show),
			"Attribute %s: read permission without 'show'\n",
			attr->attr.name);
		error = sysfs_create_file(&dev->kobj, &attr->attr);
	}
 
	return error;
}
EXPORT_SYMBOL_GPL(device_create_file);

device_create_file函数在/sys/devices/下创建结点。

sysfs_get_dirent函数的作用是增加目录parent_sd中名为name的目录或文件的引用计数。其在include/linux/sysfs.h中声明和实现，代码如下：

static inline struct kernfs_node *sysfs_get_dirent(struct kernfs_node *parent,
						   const char *name)
{
	return kernfs_find_and_get(parent, name);
}

可以看到，brightness_hw_changed_kn是在led_add_brightness_hw_changed函数中赋值的。

回到led_classdev_notify_brightness_hw_changed函数中，看最后一句：sysfs_notify_dirent(led_cdev->brightness_hw_changed_kn);。

sysfs_notify_dirent函数同样在include/linux/sysfs.h中声明和实现，代码如下：

static inline void sysfs_notify_dirent(struct kernfs_node *kn)
{
	kernfs_notify(kn);
}