if (s3c_ts_cfg->resol_bit==12) { 分频率
switch(s3c_ts_cfg->s3c_adc_con) {
case ADC_TYPE_2:
writel(readl(ts_base+S3C_ADCCON)|S3C_ADCCON_RESSEL_12BIT, ts_base+S3C_ADCCON);
break;

#define S3C_ADCCON_RESSEL_12BIT(0x1<<16)

case ADC_TYPE_1:
writel(readl(ts_base+S3C_ADCCON)|S3C_ADCCON_RESSEL_12BIT_1, ts_base+S3C_ADCCON);
break;

default:
dev_err(dev, "Touchscreen over this type of AP isn't supported !\n");
break;
}
}

writel(WAIT4INT(0), ts_base+S3C_ADCTSC);主要是对ADCTSC寄存器进行操作，使触摸屏处于等待中断模式

ts = kzalloc(sizeof(struct s3c_ts_info), GFP_KERNEL);

注：static struct s3c_ts_info*ts;

input_dev = input_allocate_device();申请并初始化一个输入设备。通过输入设备，驱动程序才能和用户交互。
注：struct input_dev *input_dev;
if (!input_dev) {
ret = -ENOMEM;
goto err_alloc;
}

ts->dev = input_dev;


ts->dev->evbit[0] = ts->dev->evbit[0] = BIT_MASK(EV_SYN) | BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
ts->dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);


if (s3c_ts_cfg->resol_bit==12) {
input_set_abs_params(ts->dev, ABS_X, 0, 0xFFF, 0, 0);
input_set_abs_params(ts->dev, ABS_Y, 0, 0xFFF, 0, 0);
}
else {
input_set_abs_params(ts->dev, ABS_X, 0, 0x3FF, 0, 0);
input_set_abs_params(ts->dev, ABS_Y, 0, 0x3FF, 0, 0);
}


input_set_abs_params(ts->dev, ABS_PRESSURE, 0, 1, 0, 0);


sprintf(ts->phys, "input(ts)");


ts->dev->name = s3c_ts_name;
ts->dev->phys = ts->phys;
ts->dev->id.bustype = BUS_RS232;
ts->dev->id.vendor = 0xDEAD;
ts->dev->id.product = 0xBEEF;
ts->dev->id.version = S3C_TSVERSION;


ts->shift = s3c_ts_cfg->oversampling_shift;
ts->resol_bit = s3c_ts_cfg->resol_bit;
ts->s3c_adc_con = s3c_ts_cfg->s3c_adc_con;

上面这一段代码都是初始化触摸屏设备的全局量ts,对应的结构体原型是：

struct s3c_ts_info {
struct input_dev *dev;
long xp;
long yp;
int count;
int shift;
char phys[32];
int resol_bit;
enum s3c_adc_types3c_adc_con;
};

/* For IRQ_PENDUP */
ts_irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0); 得到触摸屏中断IRQ_PENDUP
if (ts_irq == NULL) {
dev_err(dev, "no irq resource specified\n");
ret = -ENOENT;
goto err_irq;
}


ret = request_irq(ts_irq->start, stylus_updown, IRQF_SAMPLE_RANDOM, "s3c_updown", ts);申请触摸屏中断，对应的中断处理函数是stylus_updown
if (ret != 0) {
dev_err(dev,"s3c_ts.c: Could not allocate ts IRQ_PENDN !\n");
ret = -EIO;
goto err_irq;
}


/* For IRQ_ADC */
ts_irq = platform_get_resource(pdev, IORESOURCE_IRQ, 1); 得到ADC中断
if (ts_irq == NULL) {
dev_err(dev, "no irq resource specified\n");
ret = -ENOENT;
goto err_irq;
}


ret = request_irq(ts_irq->start, stylus_action, IRQF_SAMPLE_RANDOM, "s3c_action", ts);申请ADC中断，对应的中断函数是stylus_action
if (ret != 0) {
dev_err(dev, "s3c_ts.c: Could not allocate ts IRQ_ADC !\n");
ret = -EIO;
goto err_irq;
}


printk(KERN_INFO "%s got loaded successfully : %d bits\n", s3c_ts_name, s3c_ts_cfg->resol_bit);


/* All went ok, so register to the input system */ 将触摸屏设备注册到输入子系统中
ret = input_register_device(ts->dev);

if(ret) {
dev_err(dev, "s3c_ts.c: Could not register input device(touchscreen)!\n");
ret = -EIO;
goto fail;
}


return 0;

下面这些是错误处理代码
fail:
free_irq(ts_irq->start, ts->dev);
free_irq(ts_irq->end, ts->dev);

err_irq:
input_free_device(input_dev);
kfree(ts);


err_alloc:
clk_disable(ts_clock);
clk_put(ts_clock);

err_clk:
iounmap(ts_base);


err_map:
release_resource(ts_mem);
kfree(ts_mem);


err_req:
return ret;
}

到这里，触摸屏设备驱动的probe函数就讲述完了。