touchpanel驱动

由于最近面试多次被问道驱动相关的东西，而tp驱动次数比较多，之前也没有怎么做过，但是还是有一些接触的。下面结合实际情况整理以下吧。（本人现有一款友善之臂的4412的开发板），通过adb shell，cat /proc/bus/input/devices，cat /dev/input/event0(根据实际情况分析具体是那个节点),最终确定tp的驱动deriver.name=”ft5x0x_ts”,然后去内核中确定源码是linux-3.0.86/drivers/input/touchscreen/ft5x06_ts.c

1.驱动加载

module_init(ft5x0x_ts_init);

调用ft5x0x_ts_init函数，作用是注册一个i2c驱动

static int __init ft5x0x_ts_init(void){    return i2c_add_driver(&ft5x0x_ts_driver);}

具体i2c怎么添加一个驱动就不管了，现在来看这个ft5x0x_ts_driver这个变量

static struct i2c_driver ft5x0x_ts_driver = {    .probe      = ft5x0x_ts_probe,    .remove     = __devexit_p(ft5x0x_ts_remove),    .id_table   = ft5x0x_ts_id,    .driver = {        .name   = FT5X0X_NAME,        .owner  = THIS_MODULE,    },};

这个ft5x0x_ts_driver.driver.name = FT5X0X_NAME，就是之前cat /proc/bus/input/devices时看到的一个设备的NAME对应的值，主要分析是它的probe这个函数指针，这个就是i2c探测设备是否存在了。

probe函数内容具体如下，有注释

static int ft5x0x_ts_probe(struct i2c_client *client, const struct i2c_device_id *id){    struct ft5x0x_i2c_platform_data *pdata;    struct ft5x0x_ts_data *ts;    struct input_dev *input_dev;    unsigned char val;    unsigned int ctp_id;    int err = -EINVAL;    ctp_id = tiny4412_get_ctp();    if (ctp_id != CTP_FT5X06 && ctp_id != CTP_AUTO) {        return -ENODEV;    }    if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {        err = -ENODEV;        goto exit_check_functionality_failed;    }    ts = kzalloc(sizeof(*ts), GFP_KERNEL);    if (!ts) {        err = -ENOMEM;        goto exit_alloc_data_failed;    }    pdata = client->dev.platform_data;    if (!pdata) {        dev_err(&client->dev, "failed to get platform data\n");        goto exit_no_pdata;    }//设置ts相关的一些参数    ts->screen_max_x = pdata->screen_max_x;    ts->screen_max_y = pdata->screen_max_y;    ts->pressure_max = pdata->pressure_max;//此处感觉将gpio口当作中断来用    ts->gpio_irq = pdata->gpio_irq;    if (ts->gpio_irq != -EINVAL) {        client->irq = gpio_to_irq(ts->gpio_irq);    } else {        goto exit_no_pdata;    }    if (pdata->irq_cfg) {        s3c_gpio_cfgpin(ts->gpio_irq, pdata->irq_cfg);        s3c_gpio_setpull(ts->gpio_irq, S3C_GPIO_PULL_NONE);    }    ts->gpio_wakeup = pdata->gpio_wakeup;    ts->gpio_reset = pdata->gpio_reset;//重要，初始化work_srturt,相当于一旦需要去处理这个工作任务，那么就调用ft5x0x_ts_pen_irq_work这个方法，后面会说明    INIT_WORK(&ts->work, ft5x0x_ts_pen_irq_work);    this_client = client;    i2c_set_clientdata(client, ts);//创建一个工作队列    ts->queue = create_singlethread_workqueue(dev_name(&client->dev));    if (!ts->queue) {        err = -ESRCH;        goto exit_create_singlethread;    }//下面设置input_dev相关参数，并且注册这个input设备    input_dev = input_allocate_device();    if (!input_dev) {        err = -ENOMEM;        dev_err(&client->dev, "failed to allocate input device\n");        goto exit_input_dev_alloc_failed;    }    ts->input_dev = input_dev;    set_bit(EV_SYN, input_dev->evbit);    set_bit(EV_ABS, input_dev->evbit);    set_bit(EV_KEY, input_dev->evbit);#ifdef CONFIG_FT5X0X_MULTITOUCH    set_bit(ABS_MT_TRACKING_ID, input_dev->absbit);    set_bit(ABS_MT_TOUCH_MAJOR, input_dev->absbit);    set_bit(ABS_MT_WIDTH_MAJOR, input_dev->absbit);    set_bit(ABS_MT_POSITION_X, input_dev->absbit);    set_bit(ABS_MT_POSITION_Y, input_dev->absbit);    input_set_abs_params(input_dev, ABS_MT_POSITION_X, 0, ts->screen_max_x, 0, 0);    input_set_abs_params(input_dev, ABS_MT_POSITION_Y, 0, ts->screen_max_y, 0, 0);    input_set_abs_params(input_dev, ABS_MT_TOUCH_MAJOR, 0, ts->pressure_max, 0, 0);    input_set_abs_params(input_dev, ABS_MT_WIDTH_MAJOR, 0, 200, 0, 0);    input_set_abs_params(input_dev, ABS_MT_TRACKING_ID, 0, FT5X0X_PT_MAX, 0, 0);#else    set_bit(ABS_X, input_dev->absbit);    set_bit(ABS_Y, input_dev->absbit);    set_bit(ABS_PRESSURE, input_dev->absbit);    set_bit(BTN_TOUCH, input_dev->keybit);    input_set_abs_params(input_dev, ABS_X, 0, ts->screen_max_x, 0, 0);    input_set_abs_params(input_dev, ABS_Y, 0, ts->screen_max_y, 0, 0);    input_set_abs_params(input_dev, ABS_PRESSURE, 0, ts->pressure_max, 0 , 0);#endif    input_dev->name = FT5X0X_NAME;    input_dev->phys = "input(mt)";    input_dev->id.bustype = BUS_I2C;    input_dev->id.vendor = 0x12FA;    input_dev->id.product = 0x2143;    input_dev->id.version = 0x0100;//注册input设备    err = input_register_device(input_dev);    if (err) {        input_free_device(input_dev);        dev_err(&client->dev, "failed to register input device %s, %d\n",                dev_name(&client->dev), err);        goto exit_input_dev_alloc_failed;    }    msleep(3);    err = ft5x0x_read_fw_ver(&val);    if (err < 0) {        dev_err(&client->dev, "chip not found\n");        goto exit_irq_request_failed;    }//注册中断,一旦触发中断将会调用ft5x0x_ts_interrupt（）这个方法    err = request_irq(client->irq, ft5x0x_ts_interrupt,            IRQ_TYPE_EDGE_FALLING /*IRQF_TRIGGER_FALLING*/, "ft5x0x_ts", ts);    if (err < 0) {        dev_err(&client->dev, "Request IRQ %d failed, %d\n", client->irq, err);        goto exit_irq_request_failed;    }    disable_irq(client->irq);    dev_info(&client->dev, "Firmware version 0x%02x\n", val);#ifdef CONFIG_HAS_EARLYSUSPEND    ts->early_suspend.level = EARLY_SUSPEND_LEVEL_BLANK_SCREEN + 1;    ts->early_suspend.suspend = ft5x0x_ts_suspend;    ts->early_suspend.resume = ft5x0x_ts_resume;    register_early_suspend(&ts->early_suspend);#endif//使能中断    enable_irq(client->irq);    tiny4412_set_ctp(CTP_FT5X06);    dev_info(&client->dev, "FocalTech ft5x0x TouchScreen initialized\n");    return 0;exit_irq_request_failed:    input_unregister_device(input_dev);exit_input_dev_alloc_failed:    cancel_work_sync(&ts->work);    destroy_workqueue(ts->queue);exit_create_singlethread:    i2c_set_clientdata(client, NULL);exit_no_pdata:    kfree(ts);exit_alloc_data_failed:exit_check_functionality_failed:    dev_err(&client->dev, "probe ft5x0x TouchScreen failed, %d\n", err);    return err;}

ft5x0x_ts_interrupt这个方法大概就是disable中断，然后添加个work_struct到工作队列中，之后工作队列就会处理这个工作。

static irqreturn_t ft5x0x_ts_interrupt(int irq, void *dev_id) {    struct ft5x0x_ts_data *ts = dev_id;    disable_irq_nosync(this_client->irq);    if (!work_pending(&ts->work)) {        queue_work(ts->queue, &ts->work);    }    return IRQ_HANDLED;}

ft5x0x_ts_pen_irq_work这个方法

static void ft5x0x_ts_pen_irq_work(struct work_struct *work) {    struct ft5x0x_ts_data *ts = container_of(work, struct ft5x0x_ts_data, work);//读取tp值    if (!ft5x0x_read_data(ts)) {    //上报读取到的值        ft5x0x_ts_report(ts);    }//使能irq    enable_irq(this_client->irq);}

读取数据的方法

static int ft5x0x_read_data(struct ft5x0x_ts_data *ts) {    struct ft5x0x_event *event = &ts->event;    u8 buf[32] = { 0 };    int ret;#ifdef CONFIG_FT5X0X_MULTITOUCH    ret = ft5x0x_i2c_rxdata(buf, 31);#else    ret = ft5x0x_i2c_rxdata(buf, 7);#endif    if (ret < 0) {        printk("%s: read touch data failed, %d\n", __func__, ret);        return ret;    }    memset(event, 0, sizeof(struct ft5x0x_event));    event->touch_point = buf[2] & 0x07;    if (!event->touch_point) {        ft5x0x_ts_release(ts);        return 1;    }#ifdef CONFIG_FT5X0X_MULTITOUCH    switch (event->touch_point) {        case 5:            event->x[4] = (s16)(buf[0x1b] & 0x0F)<<8 | (s16)buf[0x1c];            event->y[4] = (s16)(buf[0x1d] & 0x0F)<<8 | (s16)buf[0x1e];        case 4:            event->x[3] = (s16)(buf[0x15] & 0x0F)<<8 | (s16)buf[0x16];            event->y[3] = (s16)(buf[0x17] & 0x0F)<<8 | (s16)buf[0x18];        case 3:            event->x[2] = (s16)(buf[0x0f] & 0x0F)<<8 | (s16)buf[0x10];            event->y[2] = (s16)(buf[0x11] & 0x0F)<<8 | (s16)buf[0x12];        case 2:            event->x[1] = (s16)(buf[0x09] & 0x0F)<<8 | (s16)buf[0x0a];            event->y[1] = (s16)(buf[0x0b] & 0x0F)<<8 | (s16)buf[0x0c];        case 1:            event->x[0] = (s16)(buf[0x03] & 0x0F)<<8 | (s16)buf[0x04];            event->y[0] = (s16)(buf[0x05] & 0x0F)<<8 | (s16)buf[0x06];            break;        default:            printk("%s: invalid touch data, %d\n", __func__, event->touch_point);            return -1;    }#else    if (event->touch_point == 1) {        event->x[0] = (s16)(buf[0x03] & 0x0F)<<8 | (s16)buf[0x04];        event->y[0] = (s16)(buf[0x05] & 0x0F)<<8 | (s16)buf[0x06];    }#endif    event->pressure = 200;    return 0;}

上报获取到的数据的方法

/*--------------------------------------------------------- * Touch core support */static void ft5x0x_ts_report(struct ft5x0x_ts_data *ts) {    struct ft5x0x_event *event = &ts->event;    int x, y;    int i;#ifdef CONFIG_FT5X0X_MULTITOUCH    for (i = 0; i < event->touch_point; i++) {        if (swap_xy) {            x = event->y[i];            y = event->x[i];        } else {            x = event->x[i];            y = event->y[i];        }        if (scal_xy) {            x = (x * ts->screen_max_x) / TOUCH_MAX_X;            y = (y * ts->screen_max_y) / TOUCH_MAX_Y;        }        input_report_abs(ts->input_dev, ABS_MT_POSITION_X, x);        input_report_abs(ts->input_dev, ABS_MT_POSITION_Y, y);        input_report_abs(ts->input_dev, ABS_MT_PRESSURE, event->pressure);        input_report_abs(ts->input_dev, ABS_MT_TOUCH_MAJOR, event->pressure);        input_report_abs(ts->input_dev, ABS_MT_TRACKING_ID, i);        input_mt_sync(ts->input_dev);    }#else    if (event->touch_point == 1) {        if (swap_xy) {            x = event->y[i];            y = event->x[i];        } else {            x = event->x[i];            y = event->y[i];        }        if (scal_xy) {            x = (x * ts->screen_max_x) / TOUCH_MAX_X;            y = (y * ts->screen_max_y) / TOUCH_MAX_Y;        }        input_report_abs(ts->input_dev, ABS_X, x);        input_report_abs(ts->input_dev, ABS_Y, y);        input_report_abs(ts->input_dev, ABS_PRESSURE, event->pressure);    }    input_report_key(ts->input_dev, BTN_TOUCH, 1);#endif    input_sync(ts->input_dev);}

上报数据的时候，对调用到linux-3.0.86/drivers/input/input.c中的一些方法（实质上注册input设备，生成设备节点等什么都是这个东西干的）。而读取数据则是i2c相关的驱动干的。基本上一个tp的驱动大概就是这些，一般工作中可能就需要通过看data来修改i2c从设备地址，vendor_id，以及寄存器等。

附：（原理图）

原理图41 42 43 3个引脚分别对应I2C的时钟线，I2C的数据线，和INT