android系统开发(四)-触摸屏tslib移植(内核)和原理分析

转自：http://blog.csdn.net/jiajie961/archive/2010/11/11/6003384.aspx

首先了解一下tslib的运行原理，tslib的运行分成两部分
(1)校验
在LCD固定坐标位置依次显示出5个坐标让用户触摸，把LCD坐标和用户触摸时驱动屏驱动底层的坐标总共5组值保存起来
运行tslib库的算法对其进行运算，得出校准用7个值

(2)校准
每次触摸屏驱动读取到硬件坐标时应用校准用的7个值对该坐标进行一次运算，然后将运算后的坐标作为正常坐标即可。

按照上面的原理，
(1)我们先修改内核部分，我的平台用的触摸屏幕驱动是tsc2007，驱动文件为内核/drivers/input/touchscreen
目录下的tsc2007.c和ts_linear.c
其中，ts_linear.c中定义的是校准模块，该模块在proc文件系统中建立了7个文件，用来存放校准用的7个点，7的点的默认值
为1,0,0,0,1,0,1，对应的目标平台文件系统的位置为/proc/sys/dev/ts_device目录下a0,a1,a2,a3,a4,a5,a6等7个文件
此模块中还定义了一个校准函数ts_linear_scale，此函数的主要内容是读取a0,a1,a2,a3,a4,a5,a6等7个文件中的值作为7个
校准值与传入的触摸平坐标值进行运算，返回运算结果。
ts_linear_scale函数定义如下：
int ts_linear_scale(int *x, int *y, int swap_xy)
{
int xtemp, ytemp;

xtemp = *x;
ytemp = *y;

if (cal.a[6] == 0)
return -EINVAL;

*x = (cal.a[2] + cal.a[0] * xtemp + cal.a[1] * ytemp) / cal.a[6];
*y = (cal.a[5] + cal.a[3] * xtemp + cal.a[4] * ytemp) / cal.a[6];

if (swap_xy) {
int tmp = *x;
*x = *y;
*y = tmp;
}
return 0;
}

ts2007.c为触摸屏驱，与其他驱动不同的地方是在取得硬件坐标值发送之前先调用了ts_linear_scale函数对坐标值进行了校准
if (x > 0 && y > 0)
{
ts_linear_scale(&x, &y, invert);
input_report_abs(input, ABS_X, x);
input_report_abs(input, ABS_Y, y);
input_report_abs(input, ABS_PRESSURE, 255);
input_report_abs(input, ABS_TOOL_WIDTH, 1);
input_report_key(input, BTN_TOUCH, 1);
input_sync(input);
}

(2)在android源代码/system/core/rootdir/init.rc文件中添加tslib相关的宏定义如下：
# touchscreen parameters
export TSLIB_FBDEVICE /dev/graphics/fb0
export TSLIB_CALIBFILE /data/etc/pointercal
export TSLIB_CONFFILE /system/etc/ts.conf
export TSLIB_TRIGGERDEV /dev/input/event0
export TSLIB_TSDEVICE /dev/input/event1

(2)移植tslib库到android系统，比较麻烦，看下一节的内容。

(3)校验程序完成后会将生成的7个校准值写入到环境变量TSLIB_CALIBFILE对应的路径/data/etc/pointercal文件中

(4)校验完后将pointercal文件中的7个值分别写入到/proc/sys/dev/ts_device目录下a0,a1,a2,a3,a4,a5,a6文件即可。

(5)开机启动的时候我们编写一个应用程序，首先判断环境变量TSLIB_CALIBFILE对应的路径/data/etc/pointercal文件是否存在，如果
文件存在而且非空，则将该文件中的7个值取出来分别写入到/proc/sys/dev/ts_device目录下a0,a1,a2,a3,a4,a5,a6文件

(6)为了确保未校验前触摸屏可用，我们将一次校验后得出的7个坐标值作为初始值，修改到内核ts_linear.c文件中。

下面是源代码：
ts_linear.c文件
/*
* Touchscreen Linear Scale Adaptor
*
* Copyright (C) 2009 Marvell Corporation
*
* Author: Mark F. Brown <markb@marvell.com>
* Based on tslib 1.0 plugin linear.c by Russel King
*
* This library is licensed under GPL.
*
*/

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/input.h>
#include <linux/interrupt.h>
#include <linux/wait.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/proc_fs.h>
#include <linux/sysctl.h>
#include <asm/system.h>

/*
* sysctl-tuning infrastructure.
*/
static struct ts_calibration {
/* Linear scaling and offset parameters for x,y (can include rotation) */
int a[7];
} cal;

static ctl_table ts_proc_calibration_table[] = {
{
.ctl_name = CTL_UNNUMBERED,
.procname = "a0",
.data = &cal.a[0],
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "a1",
.data = &cal.a[1],
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "a2",
.data = &cal.a[2],
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "a3",
.data = &cal.a[3],
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "a4",
.data = &cal.a[4],
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "a5",
.data = &cal.a[5],
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "a6",
.data = &cal.a[6],
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &proc_dointvec,
},

{.ctl_name = 0}
};

static ctl_table ts_proc_root[] = {
{
.ctl_name = CTL_UNNUMBERED,
.procname = "ts_device",
.mode = 0555,
.child = ts_proc_calibration_table,
},
{.ctl_name = 0}
};

static ctl_table ts_dev_root[] = {
{
.ctl_name = CTL_DEV,
.procname = "dev",
.mode = 0555,
.child = ts_proc_root,
},
{.ctl_name = 0}
};

static struct ctl_table_header *ts_sysctl_header;

int ts_linear_scale(int *x, int *y, int swap_xy)
{
int xtemp, ytemp;

xtemp = *x;
ytemp = *y;

if (cal.a[6] == 0)
return -EINVAL;

*x = (cal.a[2] + cal.a[0] * xtemp + cal.a[1] * ytemp) / cal.a[6];
*y = (cal.a[5] + cal.a[3] * xtemp + cal.a[4] * ytemp) / cal.a[6];

if (swap_xy) {
int tmp = *x;
*x = *y;
*y = tmp;
}
return 0;
}

EXPORT_SYMBOL(ts_linear_scale);

static int __init ts_linear_init(void)
{
ts_sysctl_header = register_sysctl_table(ts_dev_root);
/* Use default values that leave ts numbers unchanged after transform */
cal.a[0] = 1;
cal.a[1] = 0;
cal.a[2] = 0;
cal.a[3] = 0;
cal.a[4] = 1;
cal.a[5] = 0;
cal.a[6] = 1;
return 0;
}

static void __exit ts_linear_cleanup(void)
{
unregister_sysctl_table(ts_sysctl_header);
}

module_init(ts_linear_init);
module_exit(ts_linear_cleanup);

MODULE_DESCRIPTION("touch screen linear scaling driver");
MODULE_LICENSE("GPL");

ts2007.c文件
/*
* linux/drivers/input/touchscreen/tsc2007.c
*
* touch screen driver for tsc2007
*
* Copyright (C) 2006, Marvell Corporation
*
* 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/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/input.h>
#include <linux/interrupt.h>
#include <linux/wait.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/freezer.h>
#include <linux/proc_fs.h>
#include <linux/clk.h>
#include <linux/i2c.h>
#include <mach/gpio.h>

#include <linux/sysctl.h>
#include <asm/system.h>

extern int ts_linear_scale(int *x, int *y, int swap_xy);

/* Use MAV filter */
#define TSC_CMD_SETUP 0xb0

/* Use 12-bit */
#define TSC_CMD_X 0xc0
#define TSC_CMD_PLATEX 0x80
#define TSC_CMD_Y 0xd0
#define TSC_CMD_PLATEY 0x90

#define TSC_X_MAX 4096
#define TSC_Y_MAX 4096
#define TSC_X_MIN 0
#define TSC_Y_MIN 0

/* delay time for compute x, y, computed as us */

#define DEBUG
#ifdef DEBUG
#define TS_DEBUG(fmt,args...) printk(KERN_DEBUG fmt, ##args )
#else
#define TS_DEBUG(fmt,args...)
#endif
static int x_min=TSC_X_MIN;
static int y_min=TSC_Y_MIN;
static int x_max=TSC_X_MAX;
static int y_max=TSC_Y_MAX;
static int invert = 0;
static int debounce_time = 150;
static int init_debounce = true;
static int delay_time = 1;

enum tsc2007_status {
PEN_UP,
PEN_DOWN,
};

struct _tsc2007 {
struct input_dev *dev;
int x; /* X sample values */
int y; /* Y sample values */

int status;
struct work_struct irq_work;
struct i2c_client *client;
unsigned long last_touch;
};
struct _tsc2007 *g_tsc2007;

/* update abs params when min and max coordinate values are set */
int tsc2007_proc_minmax(struct ctl_table *table, int write, struct file *filp,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
struct _tsc2007 *tsc2007= g_tsc2007;
struct input_dev *input = tsc2007->dev;

/* update value */
int ret = proc_dointvec(table, write, filp, buffer, lenp, ppos);

/* updated abs params */
if (input) {
TS_DEBUG(KERN_DEBUG "update x_min %d x_max %d"
" y_min %d y_max %d/n", x_min, x_max,
y_min, y_max);
input_set_abs_params(input, ABS_X, x_min, x_max, 0, 0);
input_set_abs_params(input, ABS_Y, y_min, y_max, 0, 0);
}
return ret;
}

static ctl_table tsc2007_proc_table[] = {
{
.ctl_name = CTL_UNNUMBERED,
.procname = "x-max",
.data = &x_max,
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &tsc2007_proc_minmax,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "y-max",
.data = &y_max,
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &tsc2007_proc_minmax,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "x-min",
.data = &x_min,
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &tsc2007_proc_minmax,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "y-min",
.data = &y_min,
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &tsc2007_proc_minmax,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "invert_xy",
.data = &invert,
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "debounce_time",
.data = &debounce_time,
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "delay_time",
.data = &delay_time,
.maxlen = sizeof(int),
.mode = 0666,
.proc_handler = &proc_dointvec,
},
{ .ctl_name = 0 }
};

static ctl_table tsc2007_proc_root[] = {
{
.ctl_name = CTL_UNNUMBERED,
.procname = "ts_device",
.mode = 0555,
.child = tsc2007_proc_table,
},
{ .ctl_name = 0 }
};

static ctl_table tsc2007_proc_dev_root[] = {
{
.ctl_name = CTL_DEV,
.procname = "dev",
.mode = 0555,
.child = tsc2007_proc_root,
},
{ .ctl_name = 0 }
};

static struct ctl_table_header *sysctl_header;

static int __init init_sysctl(void)
{
sysctl_header = register_sysctl_table(tsc2007_proc_dev_root);
return 0;
}

static void __exit cleanup_sysctl(void)
{
unregister_sysctl_table(sysctl_header);
}

static int tsc2007_measure(struct i2c_client *client, int *x, int * y)
{
u8 x_buf[2] = {0, 0};
u8 y_buf[2] = {0, 0};

i2c_smbus_write_byte(client, TSC_CMD_PLATEX);
msleep_interruptible(delay_time);

i2c_smbus_write_byte(client, TSC_CMD_X);
i2c_master_recv(client, x_buf, 2);
*x = (x_buf[0]<<4) | (x_buf[1] >>4);

i2c_smbus_write_byte(client, TSC_CMD_PLATEY);
msleep_interruptible(delay_time);

i2c_smbus_write_byte(client, TSC_CMD_Y);
i2c_master_recv(client, y_buf, 2);
*y = (y_buf[0]<<4) | (y_buf[1] >>4);
*y = 4096 - *y; //added by allen
printk("/ntouchscreen x = 0x%x, y = 0x%x/n",*x,*y);
return 0;
}

static void tsc2007_irq_work(struct work_struct *work)
{
struct _tsc2007 *tsc2007= g_tsc2007;
struct i2c_client *client = tsc2007-> client;
struct input_dev *input = tsc2007->dev;

int x = -1, y = -1, is_valid = 0;
int tmp_x = 0, tmp_y = 0;

int gpio = irq_to_gpio(client->irq);

/* Ignore if PEN_DOWN */
if(PEN_UP == tsc2007->status){

if (gpio_request(gpio, "tsc2007 touch detect")) {
printk(KERN_ERR "Request GPIO failed, gpio: %X/n", gpio);
return;
}
gpio_direction_input(gpio);

while(0 == gpio_get_value(gpio)){

if ((jiffies_to_msecs(
((long)jiffies - (long)tsc2007->last_touch)) <
debounce_time &&
tsc2007->status == PEN_DOWN) ||
init_debounce)
{
init_debounce = false;
tsc2007_measure(client, &tmp_x, &tmp_y);
TS_DEBUG(KERN_DEBUG
"dropping pen touch %lu %lu (%u)/n",
jiffies, tsc2007->last_touch,
jiffies_to_msecs(
(long)jiffies - (long)tsc2007->last_touch));
schedule();
continue;
}

/* continue report x, y */
if (x > 0 && y > 0)
{
ts_linear_scale(&x, &y, invert);
input_report_abs(input, ABS_X, x);
input_report_abs(input, ABS_Y, y);
input_report_abs(input, ABS_PRESSURE, 255);
input_report_abs(input, ABS_TOOL_WIDTH, 1);
input_report_key(input, BTN_TOUCH, 1);
input_sync(input);
}

tsc2007->status = PEN_DOWN;
tsc2007_measure(client, &x, &y);
TS_DEBUG(KERN_DEBUG "pen down x=%d y=%d!/n", x, y);
is_valid = 1;
schedule();
}

if (is_valid)
{
/*consider PEN_UP */
tsc2007->status = PEN_UP;
input_report_abs(input, ABS_PRESSURE, 0);
input_report_abs(input, ABS_TOOL_WIDTH, 1);
input_report_key(input, BTN_TOUCH, 0);
input_sync(input);
tsc2007->last_touch = jiffies;
TS_DEBUG(KERN_DEBUG "pen up!/n");
}

gpio_free(gpio);
}
}

static irqreturn_t tsc2007_interrupt(int irq, void *dev_id)
{
schedule_work(&g_tsc2007->irq_work);

return IRQ_HANDLED;
}

static int __devinit tsc2007_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct _tsc2007 *tsc2007;
struct input_dev *input_dev;
int ret;

tsc2007 = kzalloc(sizeof(struct _tsc2007), GFP_KERNEL);
input_dev = input_allocate_device();

g_tsc2007 = tsc2007;

if (!tsc2007 || !input_dev) {
ret = -ENOMEM;
goto fail1;
}

i2c_set_clientdata(client, tsc2007);

tsc2007->dev = input_dev;

input_dev->name = "tsc2007";
input_dev->phys = "tsc2007/input0";

//input_dev->id.bustype = BUS_HOST;
input_dev->dev.parent = &client->dev;

__set_bit(EV_KEY, input_dev->evbit);
__set_bit(BTN_TOUCH, input_dev->keybit);

__set_bit(EV_ABS, input_dev->evbit);
__set_bit(ABS_PRESSURE, input_dev->evbit);
__set_bit(ABS_X, input_dev->evbit);
__set_bit(ABS_Y, input_dev->evbit);

input_set_abs_params(input_dev, ABS_X, x_min, x_max, 0, 0);
input_set_abs_params(input_dev, ABS_Y, y_min, y_max, 0, 0);
input_set_abs_params(input_dev, ABS_PRESSURE, 0, 255, 0, 0);

ret = request_irq(client->irq, tsc2007_interrupt,
IRQF_DISABLED | IRQF_TRIGGER_FALLING,
"tsc2007 irq", NULL);
if (ret){
printk(KERN_ERR "tsc2007 request irq failed/n");
goto fail2;
}

ret = input_register_device(tsc2007->dev);
if (ret){
printk(KERN_ERR "tsc2007 register device fail/n");
goto fail2;
}

/*init */
tsc2007->status = PEN_UP;
tsc2007->client = client;
tsc2007->last_touch = jiffies;

INIT_WORK(&tsc2007->irq_work, tsc2007_irq_work);

/* init tsc2007 */
i2c_smbus_write_byte(client, TSC_CMD_SETUP);

return 0;

fail2:
free_irq(client->irq, client);
fail1:
i2c_set_clientdata(client, NULL);
input_free_device(input_dev);
kfree(tsc2007);
return ret;
}

static int __devexit tsc2007_remove(struct i2c_client *client)
{
struct _tsc2007 *tsc2007 = i2c_get_clientdata(client);

if(client->irq)
free_irq(client->irq, client);

i2c_set_clientdata(client, NULL);
input_unregister_device(tsc2007->dev);
kfree(tsc2007);

return 0;
}

static struct i2c_device_id tsc2007_idtable[] = {
{ "tsc2007", 0 },
{ }
};

MODULE_DEVICE_TABLE(i2c, tsc2007_idtable);

static struct i2c_driver tsc2007_driver = {
.driver = {
.name = "tsc2007",
},
.id_table = tsc2007_idtable,
.probe = tsc2007_probe,
.remove = __devexit_p(tsc2007_remove),
};

static int __init tsc2007_ts_init(void)
{
init_sysctl();
return i2c_add_driver(&tsc2007_driver);
}

static void __exit tsc2007_ts_exit(void)
{
cleanup_sysctl();
i2c_del_driver(&tsc2007_driver);
}

module_init(tsc2007_ts_init);
module_exit(tsc2007_ts_exit);

MODULE_DESCRIPTION("tsc2007 touch screen driver");
MODULE_LICENSE("GPL");