9.1.触摸屏驱动概览
9.1.1、常用的2种触摸屏

(1)电阻触摸屏。驱动一般分2种:一种是SoC内置触摸屏控制器,一种是外置的专门触摸屏控制芯片,通过I2C接口和SoC通信。
(2)电容触摸屏。驱动只有一种,外接专用的电容式触摸屏控制芯片,I2C接口和SoC通信。

9.1.2、学习触摸屏驱动的关键点
(1)input子系统相关知识
(2)中断上下半部
(3)I2C子系统
(4)触摸屏芯片本身知识

9.1.3、竞争状态和同步

9.2_3.内核中的竞争状态和互斥
9.2.1、一些概念
(1)竞争状态(简称竟态)
(2)临界段、互斥锁、死锁
(3)同步(多CPU、多任务、中断)

9.2.2、解决竟态的方法
(1)原子操作 automic_t
(2)信号量、互斥锁
(3)自旋锁

9.2.3、自旋锁和信号量的使用要点
(1)自旋锁不能递归
(2)自旋锁可以用在中断上下文(信号量不可以,因为可能睡眠),但是在中断上下文中获取自旋锁之前要先禁用本地中断
(3)自旋锁的核心要求是:拥有自旋锁的代码必须不能睡眠,要一直持有CPU直到释放自旋锁
(4)信号量和读写信号量适合于保持时间较长的情况,它们会导致调用者睡眠,因此只能在进程上下文使用,而自旋锁适合于保持时间非常短的情况,它可以在任何上下文使用。如果被保护的共享资源只在进程上下文访问,使用信号量保护该共享资源非常合适,如果对共享资源的访问时间非常短,自旋锁也可以。但是如果被保护的共享资源需要在中断上下文访问(包括底半部即中断处理句柄和顶半部即软中断),就必须使用自旋锁。自旋锁保持期间是抢占失效的,而信号量和读写信号量保持期间是可以被抢占的。自旋锁只有在内核可抢占或SMP(多处理器)的情况下才真正需要,在单CPU且不可抢占的内核下,自旋锁的所有操作都是空操作。

9.4.中断的上下半部1
9.4.1、中断处理的注意点

(1)中断上下文,不能和用户空间数据交互
(2)不能交出CPU(不能休眠、不能schedule)
(3)ISR运行时间尽可能短,越长则系统响应特性越差

9.4.2、中断下半部2种解决方案
(1)为什么要分上半部(top half,又叫顶半部)和下半部(bottom half,又叫底半部)
(2)下半部处理策略1:tasklet(小任务)
(3)下半部处理策略2:workqueue(工作队列)

9.4.3、tasklet使用实战
(1)tasklet相关接口介绍
(2)实战演示tasklet实现下半部

#include <linux/input.h> 
#include <linux/module.h> 
#include <linux/init.h>
#include <asm/irq.h> 
#include <asm/io.h>

#include <mach/irqs.h>			// arch/arm/mach-s5pv210/include/mach/irqs.h
#include <linux/interrupt.h>
#include <linux/gpio.h>

/*
 * X210:
 *
 * POWER  -> EINT1   -> GPH0_1
 * LEFT   -> EINT2   -> GPH0_2
 * DOWN   -> EINT3   -> GPH0_3
 * UP     -> KP_COL0 -> GPH2_0
 * RIGHT  -> KP_COL1 -> GPH2_1
 * MENU   -> KP_COL3 -> GPH2_3 (KEY_A)
 * BACK   -> KP_COL2 -> GPH2_2 (KEY_B)
 */

#define BUTTON_IRQ	IRQ_EINT2

static struct input_dev *button_dev;

// 下半部函数
void func(unsigned long data)
{
	int flag;
	
	printk("key-s5pv210: this is bottom half\n");
	
	s3c_gpio_cfgpin(S5PV210_GPH0(2), S3C_GPIO_SFN(0x0));		// input模式
	flag = gpio_get_value(S5PV210_GPH0(2));
	s3c_gpio_cfgpin(S5PV210_GPH0(2), S3C_GPIO_SFN(0x0f));		// eint2模式

	input_report_key(button_dev, KEY_LEFT, !flag);
	input_sync(button_dev);
}

DECLARE_TASKLET(mytasklet, func, 0);

static irqreturn_t button_interrupt(int irq, void *dummy) 
{ 
	printk("key-s5pv210: this is top half\n");
	
	tasklet_schedule(&mytasklet);
	
	return IRQ_HANDLED; 
}

static int __init button_init(void) 
{ 
	int error;
	
	error = gpio_request(S5PV210_GPH0(2), "GPH0_2");
	if(error)
		printk("key-s5pv210: request gpio GPH0(2) fail");
	s3c_gpio_cfgpin(S5PV210_GPH0(2), S3C_GPIO_SFN(0x0f));		// eint2模式
	
	if (request_irq(BUTTON_IRQ, button_interrupt, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "button-x210", NULL)) 
	{ 
		printk(KERN_ERR "key-s5pv210.c: Can't allocate irq %d\n", BUTTON_IRQ);
		return -EBUSY; 
	}
	button_dev = input_allocate_device();
	if (!button_dev) 
	{ 
		printk(KERN_ERR "key-s5pv210.c: Not enough memory\n");
		error = -ENOMEM;
		goto err_free_irq; 
	}
	
	button_dev->evbit[0] = BIT_MASK(EV_KEY);
	button_dev->keybit[BIT_WORD(KEY_LEFT)] = BIT_MASK(KEY_LEFT);
	
	error = input_register_device(button_dev);
	if (error) 
	{ 
		printk(KERN_ERR "key-s5pv210.c: Failed to register device\n");
		goto err_free_dev; 
	}
	return 0;
	
err_free_dev:
	input_free_device(button_dev);
err_free_irq:
	free_irq(BUTTON_IRQ, button_interrupt);
	return error; 
}

static void __exit button_exit(void) 
{ 
	input_unregister_device(button_dev); 
	free_irq(BUTTON_IRQ, button_interrupt); 
}

module_init(button_init); 
module_exit(button_exit); 

MODULE_LICENSE("GPL");
MODULE_AUTHOR("aston <1264671872@qq.com>");
MODULE_DESCRIPTION("key driver for x210 button.");




9.5.中断的上下半部2
9.5.1、workqueue实战演示

(1)workqueue的突出特点是下半部会交给worker thead,因此下半部处于进程上下文,可以被调度,因此可以睡眠。
(2)include/linux/workqueue.h

9.5.2、中断上下半部处理原则
(1)必须立即进行紧急处理的极少量任务放入在中断的顶半部中,此时屏蔽了与自己同类型的中断,由于任务量少,所以可以迅速不受打扰地处理完紧急任务。

(2)需要较少时间的中等数量的急迫任务放在tasklet中。此时不会屏蔽任何中断(包括与自己的顶半部同类型的中断),所以不影响顶半部对紧急事务的处理;同时又不会进行用户进程调度,从而保证了自己急迫任务得以迅速完成。

(3)需要较多时间且并不急迫(允许被操作系统剥夺运行权)的大量任务放在workqueue中。此时操作系统会尽量快速处理完这个任务,但如果任务量太大,期间操作系统也会有机会调度别的用户进程运行,从而保证不会因为这个任务需要运行时间将其它用户进程无法进行。

(4)可能引起睡眠的任务放在workqueue中。因为在workqueue中睡眠是安全的。在需要获得大量的内存时、在需要获取信号量时,在需要执行阻塞式的I/O操作时,用workqueue很合适。

#include <linux/input.h> 
#include <linux/module.h> 
#include <linux/init.h>
#include <asm/irq.h> 
#include <asm/io.h>

#include <mach/irqs.h>			// arch/arm/mach-s5pv210/include/mach/irqs.h
#include <linux/interrupt.h>
#include <linux/gpio.h>
#include <linux/workqueue.h>

/*
 * X210:
 *
 * POWER  -> EINT1   -> GPH0_1
 * LEFT   -> EINT2   -> GPH0_2
 * DOWN   -> EINT3   -> GPH0_3
 * UP     -> KP_COL0 -> GPH2_0
 * RIGHT  -> KP_COL1 -> GPH2_1
 * MENU   -> KP_COL3 -> GPH2_3 (KEY_A)
 * BACK   -> KP_COL2 -> GPH2_2 (KEY_B)
 */

#define BUTTON_IRQ	IRQ_EINT2

static struct input_dev *button_dev;

// 下半部函数
void func(struct work_struct *work)
{
	int flag;
	
	printk("key-s5pv210: this is workqueue bottom half\n");
	
	s3c_gpio_cfgpin(S5PV210_GPH0(2), S3C_GPIO_SFN(0x0));		// input模式
	flag = gpio_get_value(S5PV210_GPH0(2));
	s3c_gpio_cfgpin(S5PV210_GPH0(2), S3C_GPIO_SFN(0x0f));		// eint2模式

	input_report_key(button_dev, KEY_LEFT, !flag);
	input_sync(button_dev);
}

DECLARE_WORK(mywork, func);

static irqreturn_t button_interrupt(int irq, void *dummy) 
{ 
	printk("key-s5pv210: this is workqueue top half\n");
	
	schedule_work(&mywork);
	
	return IRQ_HANDLED; 
}

static int __init button_init(void) 
{ 
	int error;
	
	error = gpio_request(S5PV210_GPH0(2), "GPH0_2");
	if(error)
		printk("key-s5pv210: request gpio GPH0(2) fail");
	s3c_gpio_cfgpin(S5PV210_GPH0(2), S3C_GPIO_SFN(0x0f));		// eint2模式
	
	if (request_irq(BUTTON_IRQ, button_interrupt, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "button-x210", NULL)) 
	{ 
		printk(KERN_ERR "key-s5pv210.c: Can't allocate irq %d\n", BUTTON_IRQ);
		return -EBUSY; 
	}
	button_dev = input_allocate_device();
	if (!button_dev) 
	{ 
		printk(KERN_ERR "key-s5pv210.c: Not enough memory\n");
		error = -ENOMEM;
		goto err_free_irq; 
	}
	
	button_dev->evbit[0] = BIT_MASK(EV_KEY);
	button_dev->keybit[BIT_WORD(KEY_LEFT)] = BIT_MASK(KEY_LEFT);
	
	error = input_register_device(button_dev);
	if (error) 
	{ 
		printk(KERN_ERR "key-s5pv210.c: Failed to register device\n");
		goto err_free_dev; 
	}
	return 0;
	
err_free_dev:
	input_free_device(button_dev);
err_free_irq:
	free_irq(BUTTON_IRQ, button_interrupt);
	return error; 
}

static void __exit button_exit(void) 
{ 
	input_unregister_device(button_dev); 
	free_irq(BUTTON_IRQ, button_interrupt); 
}

module_init(button_init); 
module_exit(button_exit); 

MODULE_LICENSE("GPL");
MODULE_AUTHOR("aston <1264671872@qq.com>");
MODULE_DESCRIPTION("key driver for x210 button.");




9.6 linux内核的I2C子系统详解
9.6.1、I2C总线汇总概览

(1)三根通信线:SCL、SDA、GND

(2)同步、串行、电平、低速、近距离

(3)总线式结构,支持多个设备挂接在同一条总线上

(4)主从式结构,通信双方必须一个为主(master)一个为从(slave),主设备掌握每次通信的主动权,从设备按照主设备的节奏被动响应。每个从设备在总线中有唯一的地址(slave address),主设备通过从地址找到自己要通信的从设备(本质是广播)。

(5)I2C主要用途就是主SoC和外围设备之间的通信,最大优势是可以在总线上扩展多个外围设备的支持。常见的各种物联网传感器芯片(如gsensor、温度、湿度、光强度、酸碱度、烟雾浓度、压力等)均使用I2C接口和主SoC进行连接。

(6)电容触摸屏芯片的多个引脚构成2个接口。一个接口是I2C的,负责和主SoC连接(本身作为从设备),主SoC通过该接口初始化及控制电容触摸屏芯片、芯片通过该接口向SoC汇报触摸事件的信息(触摸坐标等),我们使用电容触摸屏时重点关注的是这个接口;另一个接口是电容触摸板的管理接口,电容触摸屏芯片通过该接口来控制触摸板硬件。该接口是电容触摸屏公司关心的,他们的触摸屏芯片内部固件编程要处理这部分,我们使用电容触摸屏的人并不关心这里。

9.6.2、linux内核的I2C驱动框架总览
(1)I2C驱动框架的主要目标是:让驱动开发者可以在内核中方便的添加自己的I2C设备的驱动程序,从而可以更容易的在linux下驱动自己的I2C接口硬件

(2)源码中I2C相关的驱动均位于:drivers/i2c目录下。linux系统提供2种I2C驱动实现方法:第一种叫i2c-dev,对应drivers/i2c/i2c-dev.c,这种方法只是封装了主机(I2C master,一般是SoC中内置的I2C控制器)的I2C基本操作,并且向应用层提供相应的操作接口,应用层代码需要自己去实现对slave的控制和操作,所以这种I2C驱动相当于只是提供给应用层可以访问slave硬件设备的接口,本身并未对硬件做任何操作,应用需要实现对硬件的操作,因此写应用的人必须对硬件非常了解,其实相当于传统的驱动中干的活儿丢给应用去做了,所以这种I2C驱动又叫做“应用层驱动”,这种方式并不主流,它的优势是把差异化都放在应用中,这样在设备比较难缠(尤其是slave是非标准I2C时)时不用动驱动,而只需要修改应用就可以实现对各种设备的驱动。这种驱动在驱动层很简单(就是i2c-dev.c)我们就不分析了。

(3)第二种I2C驱动是所有的代码都放在驱动层实现,直接向应用层提供最终结果。应用层甚至不需要知道这里面有I2C存在,譬如电容式触摸屏驱动,直接向应用层提供/dev/input/event1的操作接口,应用层编程的人根本不知道event1中涉及到了I2C。这种是我们后续分析的重点。

9.8.linux内核的I2C子系统详解3
9.8.1、I2C子系统的4个关键结构体

(1)struct i2c_adapter I2C适配器
(2)struct i2c_algorithm I2C算法
(3)struct i2c_client I2C(从机)设备信息
(4)struct i2c_driver I2C(从机)设备驱动

9.8.2、关键文件
(1)\drivers\i2c\i2c-core.c
(2)\drivers\i2c\busses目录
(3)\drivers\i2c\algos目录

9.9.linux内核的I2C子系统详解4
9.9.1、i2c-core.c初步分析

(1)smbus代码略过
(2)模块加载和卸载:bus_register(&i2c_bus_type);

9.9.2、I2C总线的匹配机制
(1)match函数
(2)probe函数
总结:I2C总线上有2条分支:i2c_client链和i2c_driver链,当任何一个driver或者client去注册时,I2C总线都会调用match函数去对client.name和driver.id_table.name进行循环匹配。如果driver.id_table中所有的id都匹配不上则说明client并没有找到一个对应的driver,没了;如果匹配上了则标明client和driver是适用的,那么I2C总线会调用自身的probe函数,自身的probe函数又会调用driver中提供的probe函数,driver中的probe函数会对设备进行硬件初始化和后续工作。

9.9.3、核心层开放给其他部分的注册接口
(1)i2c_add_adapter/i2c_add_numbered_adapter 注册adapter的
(2)i2c_add_driver 注册driver的
(3)i2c_new_device 注册client的

9.10.linux内核的I2C子系统详解5
9.10.1、adapter模块的注册

(1)平台总线方式注册
(2)找到driver和device,并且确认其配对过程
(3)probe函数

9.10.2、probe函数分析
(1)填充一个i2c_adapter结构体,并且调用接口去注册之
(2)从platform_device接收硬件信息,做必要的处理(request_mem_region & ioremap、request_irq等)
(3)对硬件做初始化(直接操作210内部I2C控制器的寄存器)

9.10.3、i2c_algorithm
(1)i2c->adap.algo = &s3c24xx_i2c_algorithm;
(2)functionality
(3)s3c24xx_i2c_doxfer

9.11_12.linux内核的I2C子系统详解6_7
9.11.1、i2c_driver的注册

(1)以gslX680的驱动为例
(2)将驱动添加到内核SI项目中
(3)i2c_driver的基本分析:name和probe

9.11.2、i2c_client从哪里来
(1)直接来源:i2c_register_board_info
smdkc110_machine_init
i2c_register_board_info

struct i2c_board_info {
char type[I2C_NAME_SIZE]; // 设备名
unsigned short flags; // 属性
unsigned short addr; // 设备从地址
void *platform_data; // 设备私有数据
struct dev_archdata *archdata;
#ifdef CONFIG_OF
struct device_node *of_node;
#endif
int irq; // 设备使用的IRQ号,对应CPU的EINT
};

(2)实现原理分析
内核维护一个链表 __i2c_board_list,这个链表上链接的是I2C总线上挂接的所有硬件设备的信息结构体。也就是说这个链表维护的是一个struct i2c_board_info结构体链表。
真正的需要的struct i2c_client在别的地方由__i2c_board_list链表中的各个节点内容来另外构建生成。

函数调用层次:
i2c_add_adapter/i2c_add_numbered_adapter
i2c_register_adapter
i2c_scan_static_board_info
i2c_new_device
device_register

总结:I2C总线的i2c_client的提供是内核通过i2c_add_adapter/i2c_add_numbered_adapter接口调用时自动生成的,生成的原料是mach-x210.c中的i2c_register_board_info(1, i2c_devs1, ARRAY_SIZE(i2c_devs1));

9.13. goodix驱动的移植实践
源码目录:\input\touchscreen\goodix.c

完整代码:

/*
 *  Driver for Goodix Touchscreens
 *
 *  Copyright (c) 2014 Red Hat Inc.
 *  Copyright (c) 2015 K. Merker <merker@debian.org>
 *
 *  This code is based on gt9xx.c authored by andrew@goodix.com:
 *
 *  2010 - 2012 Goodix Technology.
 */

/*
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; version 2 of the License.
 */

#include <linux/kernel.h>
#include <linux/dmi.h>
#include <linux/firmware.h>
#include <linux/gpio/consumer.h>
#include <linux/i2c.h>
#include <linux/input.h>
#include <linux/input/mt.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/acpi.h>
#include <linux/of.h>
#include <asm/unaligned.h>
#include "../../gpio/gpiolib.h"



struct goodix_ts_data {
	struct i2c_client *client;
	struct input_dev *input_dev;
	int abs_x_max;
	int abs_y_max;
	bool swapped_x_y;
	bool inverted_x;
	bool inverted_y;
	unsigned int max_touch_num;
	unsigned int int_trigger_type;
	int cfg_len;
	struct gpio_desc *gpiod_int;
	struct gpio_desc *gpiod_rst;
	u16 id;
	u16 version;
	const char *cfg_name;
	struct completion firmware_loading_complete;
	unsigned long irq_flags;
};

#define GOODIX_GPIO_INT_NAME		"irq"
//#define GOODIX_GPIO_RST_NAME		"reset"
#define GOODIX_GPIO_RST_NAME		"rst"


#define GOODIX_MAX_HEIGHT		854
#define GOODIX_MAX_WIDTH		480
#define GOODIX_INT_TRIGGER		1
#define GOODIX_CONTACT_SIZE		8
#define GOODIX_MAX_CONTACTS		10

#define GOODIX_CONFIG_MAX_LENGTH	240
#define GOODIX_CONFIG_911_LENGTH	186
#define GOODIX_CONFIG_967_LENGTH	228

/* Register defines */
#define GOODIX_REG_COMMAND		0x8040
#define GOODIX_CMD_SCREEN_OFF		0x05

#define GOODIX_READ_COOR_ADDR		0x814E
#define GOODIX_REG_CONFIG_DATA		0x8047
#define GOODIX_REG_ID			0x8140

#define GOODIX_BUFFER_STATUS_READY	BIT(7)
#define GOODIX_BUFFER_STATUS_TIMEOUT	20

#define RESOLUTION_LOC		1
#define MAX_CONTACTS_LOC	5
#define TRIGGER_LOC		6

static const unsigned long goodix_irq_flags[] = {
	IRQ_TYPE_EDGE_RISING,
	IRQ_TYPE_EDGE_FALLING,
	IRQ_TYPE_LEVEL_LOW,
	IRQ_TYPE_LEVEL_HIGH,
};

/*
 * Those tablets have their coordinates origin at the bottom right
 * of the tablet, as if rotated 180 degrees
 */
static const struct dmi_system_id rotated_screen[] = {
#if defined(CONFIG_DMI) && defined(CONFIG_X86)
	{
		.ident = "WinBook TW100",
		.matches = {
			DMI_MATCH(DMI_SYS_VENDOR, "WinBook"),
			DMI_MATCH(DMI_PRODUCT_NAME, "TW100")
		}
	},
	{
		.ident = "WinBook TW700",
		.matches = {
			DMI_MATCH(DMI_SYS_VENDOR, "WinBook"),
			DMI_MATCH(DMI_PRODUCT_NAME, "TW700")
		},
	},
#endif
	{}
};

/**
 * goodix_i2c_read - read data from a register of the i2c slave device.
 *
 * @client: i2c device.
 * @reg: the register to read from.
 * @buf: raw write data buffer.
 * @len: length of the buffer to write
 */
static int goodix_i2c_read(struct i2c_client *client,
			   u16 reg, u8 *buf, int len)
{
	struct i2c_msg msgs[2];
	u16 wbuf = cpu_to_be16(reg);
	int ret;

	msgs[0].flags = 0;
	msgs[0].addr  = client->addr;
	msgs[0].len   = 2;
	msgs[0].buf   = (u8 *)&wbuf;

	msgs[1].flags = I2C_M_RD;
	msgs[1].addr  = client->addr;
	msgs[1].len   = len;
	msgs[1].buf   = buf;

	ret = i2c_transfer(client->adapter, msgs, 2);
	return ret < 0 ? ret : (ret != ARRAY_SIZE(msgs) ? -EIO : 0);
}

/**
 * goodix_i2c_write - write data to a register of the i2c slave device.
 *
 * @client: i2c device.
 * @reg: the register to write to.
 * @buf: raw data buffer to write.
 * @len: length of the buffer to write
 */
static int goodix_i2c_write(struct i2c_client *client, u16 reg, const u8 *buf,
			    unsigned len)
{
	u8 *addr_buf;
	struct i2c_msg msg;
	int ret;

	addr_buf = kmalloc(len + 2, GFP_KERNEL);
	if (!addr_buf)
		return -ENOMEM;

	addr_buf[0] = reg >> 8;
	addr_buf[1] = reg & 0xFF;
	memcpy(&addr_buf[2], buf, len);

	msg.flags = 0;
	msg.addr = client->addr;
	msg.buf = addr_buf;
	msg.len = len + 2;

	ret = i2c_transfer(client->adapter, &msg, 1);
	kfree(addr_buf);
	return ret < 0 ? ret : (ret != 1 ? -EIO : 0);
}

static int goodix_i2c_write_u8(struct i2c_client *client, u16 reg, u8 value)
{
	return goodix_i2c_write(client, reg, &value, sizeof(value));
}

static int goodix_get_cfg_len(u16 id)
{
	switch (id) {
	case 911:
	case 9271:
	case 9110:
	case 927:
	case 928:
		return GOODIX_CONFIG_911_LENGTH;

	case 912:
	case 967:
		return GOODIX_CONFIG_967_LENGTH;

	default:
		return GOODIX_CONFIG_MAX_LENGTH;
	}
}

static int goodix_ts_read_input_report(struct goodix_ts_data *ts, u8 *data)
{
	unsigned long max_timeout;
	int touch_num;
	int error;

	/*
	 * The 'buffer status' bit, which indicates that the data is valid, is
	 * not set as soon as the interrupt is raised, but slightly after.
	 * This takes around 10 ms to happen, so we poll for 20 ms.
	 */
	max_timeout = jiffies + msecs_to_jiffies(GOODIX_BUFFER_STATUS_TIMEOUT);
	do {
		error = goodix_i2c_read(ts->client, GOODIX_READ_COOR_ADDR,
					data, GOODIX_CONTACT_SIZE + 1);
		if (error) {
			dev_err(&ts->client->dev, "I2C transfer error: %d\n",
					error);
			return error;
		}

		if (data[0] & GOODIX_BUFFER_STATUS_READY) {
			touch_num = data[0] & 0x0f;
			if (touch_num > ts->max_touch_num)
				return -EPROTO;
			if((data[0]&0x80)==0)//坐标未就绪,数据无效
				return -EPROTO;
			if (touch_num > 1) {
				data += 1 + GOODIX_CONTACT_SIZE;
				error = goodix_i2c_read(ts->client,
						GOODIX_READ_COOR_ADDR +
							1 + GOODIX_CONTACT_SIZE,
						data,
						GOODIX_CONTACT_SIZE *
							(touch_num - 1));
				if (error)
					return error;
			}

			return touch_num;
		}

		usleep_range(1000, 2000); /* Poll every 1 - 2 ms */
	} while (time_before(jiffies, max_timeout));

	/*
	 * The Goodix panel will send spurious interrupts after a
	 * 'finger up' event, which will always cause a timeout.
	 */
	return 0;
}

static void goodix_ts_report_touch(struct goodix_ts_data *ts, u8 *coor_data)
{
	int id = coor_data[0] & 0x0F;
	int input_x = get_unaligned_le16(&coor_data[1]);
	int input_y = get_unaligned_le16(&coor_data[3]);
	int input_w = get_unaligned_le16(&coor_data[5]);

	/* Inversions have to happen before axis swapping */
	if (ts->inverted_x)
		input_x = ts->abs_x_max - input_x;
	if (ts->inverted_y)
		input_y = ts->abs_y_max - input_y;
	if (ts->swapped_x_y)
		swap(input_x, input_y);

	input_mt_slot(ts->input_dev, id);
	input_mt_report_slot_state(ts->input_dev, MT_TOOL_FINGER, true);
	input_report_abs(ts->input_dev, ABS_MT_POSITION_X, input_x);
	input_report_abs(ts->input_dev, ABS_MT_POSITION_Y, input_y);
	input_report_abs(ts->input_dev, ABS_MT_TOUCH_MAJOR, input_w);
	input_report_abs(ts->input_dev, ABS_MT_WIDTH_MAJOR, input_w);
}

/**
 * goodix_process_events - Process incoming events
 *
 * @ts: our goodix_ts_data pointer
 *
 * Called when the IRQ is triggered. Read the current device state, and push
 * the input events to the user space.
 */
static void goodix_process_events(struct goodix_ts_data *ts)
{
	u8  point_data[1 + GOODIX_CONTACT_SIZE * GOODIX_MAX_CONTACTS];
	int touch_num;
	int i;

	touch_num = goodix_ts_read_input_report(ts, point_data);
	if (touch_num < 0)
		return;

	/*
	 * Bit 4 of the first byte reports the status of the capacitive
	 * Windows/Home button.
	 */
	input_report_key(ts->input_dev, KEY_LEFTMETA, point_data[0] & BIT(4));

	for (i = 0; i < touch_num; i++)
		goodix_ts_report_touch(ts,
				&point_data[1 + GOODIX_CONTACT_SIZE * i]);

	input_mt_sync_frame(ts->input_dev);
	input_sync(ts->input_dev);
}

/**
 * goodix_ts_irq_handler - The IRQ handler
 *
 * @irq: interrupt number.
 * @dev_id: private data pointer.
 */
static irqreturn_t goodix_ts_irq_handler(int irq, void *dev_id)
{
	struct goodix_ts_data *ts = dev_id;

	goodix_process_events(ts);

	if (goodix_i2c_write_u8(ts->client, GOODIX_READ_COOR_ADDR, 0) < 0)
		dev_err(&ts->client->dev, "I2C write end_cmd error\n");

	return IRQ_HANDLED;
}

static void goodix_free_irq(struct goodix_ts_data *ts)
{
	devm_free_irq(&ts->client->dev, ts->client->irq, ts);
}

static int goodix_request_irq(struct goodix_ts_data *ts)
{
	return devm_request_threaded_irq(&ts->client->dev, ts->client->irq,
					 NULL, goodix_ts_irq_handler,
					 ts->irq_flags, ts->client->name, ts);
}

/**
 * goodix_check_cfg - Checks if config fw is valid
 *
 * @ts: goodix_ts_data pointer
 * @cfg: firmware config data
 */
static int goodix_check_cfg(struct goodix_ts_data *ts,
			    const struct firmware *cfg)
{
	int i, raw_cfg_len;
	u8 check_sum = 0;

	if (cfg->size > GOODIX_CONFIG_MAX_LENGTH) {
		dev_err(&ts->client->dev,
			"The length of the config fw is not correct");
		return -EINVAL;
	}

	raw_cfg_len = cfg->size - 2;
	for (i = 0; i < raw_cfg_len; i++)
		check_sum += cfg->data[i];
	check_sum = (~check_sum) + 1;
	if (check_sum != cfg->data[raw_cfg_len]) {
		dev_err(&ts->client->dev,
			"The checksum of the config fw is not correct");
		return -EINVAL;
	}

	if (cfg->data[raw_cfg_len + 1] != 1) {
		dev_err(&ts->client->dev,
			"Config fw must have Config_Fresh register set");
		return -EINVAL;
	}

	return 0;
}

/**
 * goodix_send_cfg - Write fw config to device
 *
 * @ts: goodix_ts_data pointer
 * @cfg: config firmware to write to device
 */
static int goodix_send_cfg(struct goodix_ts_data *ts,
			   const struct firmware *cfg)
{
	int error;

	error = goodix_check_cfg(ts, cfg);
	if (error)
		return error;

	error = goodix_i2c_write(ts->client, GOODIX_REG_CONFIG_DATA, cfg->data,
				 cfg->size);
	if (error) {
		dev_err(&ts->client->dev, "Failed to write config data: %d",
			error);
		return error;
	}
	dev_dbg(&ts->client->dev, "Config sent successfully.");

	/* Let the firmware reconfigure itself, so sleep for 10ms */
	usleep_range(10000, 11000);

	return 0;
}

static int goodix_int_sync(struct goodix_ts_data *ts)
{
	int error;

	error = gpiod_direction_output(ts->gpiod_int, 0);
	if (error)
		return error;

	msleep(50);				/* T5: 50ms */

	error = gpiod_direction_input(ts->gpiod_int);
	if (error)
		return error;

	return 0;
}

/**
 * goodix_reset - Reset device during power on
 *
 * @ts: goodix_ts_data pointer
 */
static int goodix_reset(struct goodix_ts_data *ts)
{
	int error;

	/* begin select I2C slave addr */
	error = gpiod_direction_output(ts->gpiod_rst, 0);	
	if (error)
		return error;

	msleep(15);	

	/* HIGH: 0x28/0x29, LOW: 0xBA/0xBB */
	error = gpiod_direction_output(ts->gpiod_int, ts->client->addr == 0x14);
	if (error)
	{
		printk("[log]gpiod_direction_output int 1 err\r\n");
		return error;
	}
		
	usleep_range(100, 2000);		/* T3: > 100us */

	error = gpiod_direction_output(ts->gpiod_rst, 1);	
	if (error)
	{
		printk("[log]gpiod_direction_output rst 1 err\r\n");
		return error;
	}
		

	usleep_range(6000, 10000);		/* T4: > 5ms */

	
	/* end select I2C slave addr */
	//error = gpiod_direction_input(ts->gpiod_rst);
	//if (error)
	//	return error;
	
	//msleep(50);				/* T5: 50ms */

	error = goodix_int_sync(ts);
	if (error)
		return error;

	return 0;
}

/**
 * goodix_get_gpio_config - Get GPIO config from ACPI/DT
 *
 * @ts: goodix_ts_data pointer
 */
static int goodix_get_gpio_config(struct goodix_ts_data *ts)
{
	int error;
	struct device *dev;
	struct gpio_desc *gpiod;

	if (!ts->client)
		return -EINVAL;
	dev = &ts->client->dev;

	/* Get the interrupt GPIO pin number */
	gpiod = devm_gpiod_get_optional(dev, GOODIX_GPIO_INT_NAME, GPIOD_IN);
	
	if (IS_ERR(gpiod)) {
		error = PTR_ERR(gpiod);
		if (error != -EPROBE_DEFER)
			dev_dbg(dev, "Failed to get %s GPIO: %d\n",
				GOODIX_GPIO_INT_NAME, error);
		return error;
	}

	ts->gpiod_int = gpiod;

	/* Get the reset line GPIO pin number */
	gpiod = devm_gpiod_get_optional(dev, GOODIX_GPIO_RST_NAME, GPIOD_IN);
	if (IS_ERR(gpiod)) {
		error = PTR_ERR(gpiod);
		if (error != -EPROBE_DEFER)
			dev_dbg(dev, "Failed to get %s GPIO: %d\n",
				GOODIX_GPIO_RST_NAME, error);
		return error;
	}

	ts->gpiod_rst = gpiod;

	return 0;
}

/**
 * goodix_read_config - Read the embedded configuration of the panel
 *
 * @ts: our goodix_ts_data pointer
 *
 * Must be called during probe
 */
static void goodix_read_config(struct goodix_ts_data *ts)
{
	u8 config[GOODIX_CONFIG_MAX_LENGTH];
	int error;

	error = goodix_i2c_read(ts->client, GOODIX_REG_CONFIG_DATA,
				config, ts->cfg_len);
	if (error) {
		dev_warn(&ts->client->dev,
			 "Error reading config (%d), using defaults\n",
			 error);
		ts->abs_x_max = GOODIX_MAX_WIDTH;
		ts->abs_y_max = GOODIX_MAX_HEIGHT;
		if (ts->swapped_x_y)
			swap(ts->abs_x_max, ts->abs_y_max);
		ts->int_trigger_type = GOODIX_INT_TRIGGER;
		ts->max_touch_num = GOODIX_MAX_CONTACTS;
		return;
	}

	ts->abs_x_max = get_unaligned_le16(&config[RESOLUTION_LOC]);
	ts->abs_y_max = get_unaligned_le16(&config[RESOLUTION_LOC + 2]);
	if (ts->swapped_x_y)
		swap(ts->abs_x_max, ts->abs_y_max);
	ts->int_trigger_type = config[TRIGGER_LOC] & 0x03;
	ts->max_touch_num = config[MAX_CONTACTS_LOC] & 0x0f;
	if (!ts->abs_x_max || !ts->abs_y_max || !ts->max_touch_num) {
		dev_err(&ts->client->dev,
			"Invalid config, using defaults\n");
		ts->abs_x_max = GOODIX_MAX_WIDTH;
		ts->abs_y_max = GOODIX_MAX_HEIGHT;
		if (ts->swapped_x_y)
			swap(ts->abs_x_max, ts->abs_y_max);
		ts->max_touch_num = GOODIX_MAX_CONTACTS;
	}

	if (dmi_check_system(rotated_screen)) {
		ts->inverted_x = true;
		ts->inverted_y = true;
		dev_dbg(&ts->client->dev,
			 "Applying '180 degrees rotated screen' quirk\n");
	}
}

/**
 * goodix_read_version - Read goodix touchscreen version
 *
 * @ts: our goodix_ts_data pointer
 */
static int goodix_read_version(struct goodix_ts_data *ts)
{
	int error;
	u8 buf[6];
	char id_str[5];

	error = goodix_i2c_read(ts->client, GOODIX_REG_ID, buf, sizeof(buf));
	if (error) {
		dev_err(&ts->client->dev, "read version failed: %d\n", error);
		return error;
	}

	memcpy(id_str, buf, 4);
	id_str[4] = 0;
	if (kstrtou16(id_str, 10, &ts->id))
		ts->id = 0x1001;

	ts->version = get_unaligned_le16(&buf[4]);

	dev_info(&ts->client->dev, "ID %d, version: %04x\n", ts->id,
		 ts->version);

	return 0;
}

/**
 * goodix_i2c_test - I2C test function to check if the device answers.
 *
 * @client: the i2c client
 */
static int goodix_i2c_test(struct i2c_client *client)
{
	int retry = 0;
	int error;
	u8 test;

	while (retry++ < 2) {
		error = goodix_i2c_read(client, GOODIX_REG_CONFIG_DATA,
					&test, 1);
		if (!error)
			return 0;

		dev_err(&client->dev, "i2c test failed attempt %d: %d\n",
			retry, error);
		msleep(20);
	}

	return error;
}

/**
 * goodix_request_input_dev - Allocate, populate and register the input device
 *
 * @ts: our goodix_ts_data pointer
 *
 * Must be called during probe
 */
static int goodix_request_input_dev(struct goodix_ts_data *ts)
{
	int error;

	ts->input_dev = devm_input_allocate_device(&ts->client->dev);
	if (!ts->input_dev) {
		dev_err(&ts->client->dev, "Failed to allocate input device.");
		return -ENOMEM;
	}

	input_set_abs_params(ts->input_dev, ABS_MT_POSITION_X,
			     0, ts->abs_x_max, 0, 0);
	input_set_abs_params(ts->input_dev, ABS_MT_POSITION_Y,
			     0, ts->abs_y_max, 0, 0);
	input_set_abs_params(ts->input_dev, ABS_MT_WIDTH_MAJOR, 0, 255, 0, 0);
	input_set_abs_params(ts->input_dev, ABS_MT_TOUCH_MAJOR, 0, 255, 0, 0);

	input_mt_init_slots(ts->input_dev, ts->max_touch_num,
			    INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);

	ts->input_dev->name = "Goodix Capacitive TouchScreen";
	ts->input_dev->phys = "input/ts";
	ts->input_dev->id.bustype = BUS_I2C;
	ts->input_dev->id.vendor = 0x0416;
	ts->input_dev->id.product = ts->id;
	ts->input_dev->id.version = ts->version;

	/* Capacitive Windows/Home button on some devices */
	input_set_capability(ts->input_dev, EV_KEY, KEY_LEFTMETA);

	error = input_register_device(ts->input_dev);
	if (error) {
		dev_err(&ts->client->dev,
			"Failed to register input device: %d", error);
		return error;
	}

	return 0;
}

/**
 * goodix_configure_dev - Finish device initialization
 *
 * @ts: our goodix_ts_data pointer
 *
 * Must be called from probe to finish initialization of the device.
 * Contains the common initialization code for both devices that
 * declare gpio pins and devices that do not. It is either called
 * directly from probe or from request_firmware_wait callback.
 */
static int goodix_configure_dev(struct goodix_ts_data *ts)
{
	int error;

	ts->swapped_x_y = device_property_read_bool(&ts->client->dev,
						    "touchscreen-swapped-x-y");
	ts->inverted_x = device_property_read_bool(&ts->client->dev,
						   "touchscreen-inverted-x");
	ts->inverted_y = device_property_read_bool(&ts->client->dev,
						   "touchscreen-inverted-y");

	goodix_read_config(ts);

	error = goodix_request_input_dev(ts);
	if (error)
		return error;

	ts->irq_flags = goodix_irq_flags[ts->int_trigger_type] | IRQF_ONESHOT;
	error = goodix_request_irq(ts);
	if (error) {
		dev_err(&ts->client->dev, "request IRQ failed: %d\n", error);
		return error;
	}

	return 0;
}

/**
 * goodix_config_cb - Callback to finish device init
 *
 * @ts: our goodix_ts_data pointer
 *
 * request_firmware_wait callback that finishes
 * initialization of the device.
 */
static void goodix_config_cb(const struct firmware *cfg, void *ctx)
{
	struct goodix_ts_data *ts = ctx;
	int error;

	if (cfg) {
		/* send device configuration to the firmware */
		error = goodix_send_cfg(ts, cfg);
		if (error)
			goto err_release_cfg;
	}

	goodix_configure_dev(ts);

err_release_cfg:
	release_firmware(cfg);
	complete_all(&ts->firmware_loading_complete);
}

static int goodix_ts_probe(struct i2c_client *client,
			   const struct i2c_device_id *id)
{
	struct goodix_ts_data *ts;
	int error;

	dev_dbg(&client->dev, "I2C Address: 0x%02x\n", client->addr);

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
		dev_err(&client->dev, "I2C check functionality failed.\n");
		return -ENXIO;
	}

	ts = devm_kzalloc(&client->dev, sizeof(*ts), GFP_KERNEL);
	if (!ts)
		return -ENOMEM;

	ts->client = client;
	i2c_set_clientdata(client, ts);
	init_completion(&ts->firmware_loading_complete);

	error = goodix_get_gpio_config(ts);
	if (error)
	{
		printk("[log]goodix_get_gpio_config\r\n");
		return error;
	}
		

	if (ts->gpiod_int && ts->gpiod_rst) {
		/* reset the controller */
		error = goodix_reset(ts);
		if (error) {
			dev_err(&client->dev, "Controller reset failed.\n");
			return error;
		}
	}

	error = goodix_i2c_test(client);
	if (error) {
		printk("[log]I2C communication failure: %d\n",error);
		dev_err(&client->dev, "I2C communication failure: %d\n", error);
		return error;
	}

	error = goodix_read_version(ts);
	if (error) {
		printk("[log]Read version failed.\n");
		dev_err(&client->dev, "Read version failed.\n");
		return error;
	}

	ts->cfg_len = goodix_get_cfg_len(ts->id);

	if (ts->gpiod_int && ts->gpiod_rst) {
		/* update device config */
		ts->cfg_name = devm_kasprintf(&client->dev, GFP_KERNEL,
					      "goodix_%d_cfg.bin", ts->id);
		if (!ts->cfg_name)
			return -ENOMEM;

		error = request_firmware_nowait(THIS_MODULE, true, ts->cfg_name,
						&client->dev, GFP_KERNEL, ts,
						goodix_config_cb);
		if (error) {
			dev_err(&client->dev,
				"Failed to invoke firmware loader: %d\n",
				error);
			return error;
		}

		return 0;
	} else {
		error = goodix_configure_dev(ts);
		if (error)
			return error;
	}

	return 0;
}

static int goodix_ts_remove(struct i2c_client *client)
{
	struct goodix_ts_data *ts = i2c_get_clientdata(client);

	if (ts->gpiod_int && ts->gpiod_rst)
		wait_for_completion(&ts->firmware_loading_complete);

	return 0;
}

static int __maybe_unused goodix_suspend(struct device *dev)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct goodix_ts_data *ts = i2c_get_clientdata(client);
	int error;

	/* We need gpio pins to suspend/resume */
	if (!ts->gpiod_int || !ts->gpiod_rst) {
		disable_irq(client->irq);
		return 0;
	}

	wait_for_completion(&ts->firmware_loading_complete);

	/* Free IRQ as IRQ pin is used as output in the suspend sequence */
	goodix_free_irq(ts);

	/* Output LOW on the INT pin for 5 ms */
	error = gpiod_direction_output(ts->gpiod_int, 0);
	if (error) {
		goodix_request_irq(ts);
		return error;
	}

	usleep_range(5000, 6000);

	error = goodix_i2c_write_u8(ts->client, GOODIX_REG_COMMAND,
				    GOODIX_CMD_SCREEN_OFF);
	if (error) {
		dev_err(&ts->client->dev, "Screen off command failed\n");
		gpiod_direction_input(ts->gpiod_int);
		goodix_request_irq(ts);
		return -EAGAIN;
	}

	/*
	 * The datasheet specifies that the interval between sending screen-off
	 * command and wake-up should be longer than 58 ms. To avoid waking up
	 * sooner, delay 58ms here.
	 */
	msleep(58);
	return 0;
}

static int __maybe_unused goodix_resume(struct device *dev)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct goodix_ts_data *ts = i2c_get_clientdata(client);
	int error;

	if (!ts->gpiod_int || !ts->gpiod_rst) {
		enable_irq(client->irq);
		return 0;
	}

	/*
	 * Exit sleep mode by outputting HIGH level to INT pin
	 * for 2ms~5ms.
	 */
	error = gpiod_direction_output(ts->gpiod_int, 1);
	if (error)
		return error;

	usleep_range(2000, 5000);

	error = goodix_int_sync(ts);
	if (error)
		return error;

	error = goodix_request_irq(ts);
	if (error)
		return error;

	return 0;
}

static SIMPLE_DEV_PM_OPS(goodix_pm_ops, goodix_suspend, goodix_resume);

static const struct i2c_device_id goodix_ts_id[] = {
	{ "GDIX1001:00", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, goodix_ts_id);

#ifdef CONFIG_ACPI
static const struct acpi_device_id goodix_acpi_match[] = {
	{ "GDIX1001", 0 },
	{ "GDIX1002", 0 },
	{ }
};
MODULE_DEVICE_TABLE(acpi, goodix_acpi_match);
#endif

#ifdef CONFIG_OF
static const struct of_device_id goodix_of_match[] = {
	{ .compatible = "goodix,gt911" },
	{ .compatible = "goodix,gt9110" },
	{ .compatible = "goodix,gt912" },
	{ .compatible = "goodix,gt927" },
	{ .compatible = "goodix,gt9271" },
	{ .compatible = "goodix,gt928" },
	{ .compatible = "goodix,gt967" },
	{ }
};
MODULE_DEVICE_TABLE(of, goodix_of_match);
#endif

static struct i2c_driver goodix_ts_driver = {
	.probe = goodix_ts_probe,
	.remove = goodix_ts_remove,
	.id_table = goodix_ts_id,
	.driver = {
		.name = "Goodix-TS",
		.acpi_match_table = ACPI_PTR(goodix_acpi_match),
		.of_match_table = of_match_ptr(goodix_of_match),
		.pm = &goodix_pm_ops,
	},
};
module_i2c_driver(goodix_ts_driver);

MODULE_AUTHOR("Benjamin Tissoires <benjamin.tissoires@gmail.com>");
MODULE_AUTHOR("Bastien Nocera <hadess@hadess.net>");
MODULE_DESCRIPTION("Goodix touchscreen driver");
MODULE_LICENSE("GPL v2");

9.13.2、在内核配置中添加CONFIG项
(1)定义一个宏名,譬如CONFIG_TOUCHSCREEN_GOODIX
(2)在代码中使用宏来条件编译
(3)在Makefile中使用宏来条件配置
obj-$(CONFIG_TOUCHSCREEN_GOODIX)    += goodix.o

(4)在Kconfig项目中添加宏的配置项
config TOUCHSCREEN_GOODIX
    tristate "Goodix I2C touchscreen"
    depends on I2C
    depends on GPIOLIB || COMPILE_TEST
    help
      Say Y here if you have the Goodix touchscreen (such as one
      installed in Onda v975w tablets) connected to your
      system. It also supports 5-finger chip models, which can be
      found on ARM tablets, like Wexler TAB7200 and MSI Primo73.

      If unsure, say N.

      To compile this driver as a module, choose M here: the
      module will be called goodix.

(5)make menuconfig并选择Y或者N

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