linux触摸屏驱动分析,基于TSC2007

/*
 * drivers/input/touchscreen/tsc2007.c
 *
 * Copyright (c) 2008 MtekVision Co., Ltd.
 *  Kwangwoo Lee <[e-mail]>
 *
 * Using code from:
 *  - ads7846.c
 *  Copyright (c) 2005 David Brownell
 *  Copyright (c) 2006 Nokia Corporation
 *  - corgi_ts.c
 *  Copyright (C) 2004-2005 Richard Purdie
 *  - omap_ts.[hc], ads7846.h, ts_osk.c
 *  Copyright (C) 2002 MontaVista Software
 *  Copyright (C) 2004 Texas Instruments
 *  Copyright (C) 2005 Dirk Behme
 *
 *  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
#include
#include
#include
#include
#include
#define TS_POLL_DELAY           1 /* ms delay between samples */
#define TS_POLL_PERIOD          1 /* ms delay between samples */
#define TSC2007_MEASURE_TEMP0       (0x0 << 4)
#define TSC2007_MEASURE_AUX     (0x2 << 4)
#define TSC2007_MEASURE_TEMP1       (0x4 << 4)
#define TSC2007_ACTIVATE_XN     (0x8 << 4)
#define TSC2007_ACTIVATE_YN     (0x9 << 4)
#define TSC2007_ACTIVATE_YP_XN      (0xa << 4)
#define TSC2007_SETUP           (0xb << 4)
#define TSC2007_MEASURE_X       (0xc << 4)
#define TSC2007_MEASURE_Y       (0xd << 4)
#define TSC2007_MEASURE_Z1      (0xe << 4)
#define TSC2007_MEASURE_Z2      (0xf << 4)
#define TSC2007_POWER_OFF_IRQ_EN    (0x0 << 2)
#define TSC2007_ADC_ON_IRQ_DIS0     (0x1 << 2)
#define TSC2007_ADC_OFF_IRQ_EN      (0x2 << 2)
#define TSC2007_ADC_ON_IRQ_DIS1     (0x3 << 2)
#define TSC2007_12BIT           (0x0 << 1)
#define TSC2007_8BIT            (0x1 << 1)
#define MAX_12BIT           ((1 << 12) - 1)
#define ADC_ON_12BIT    (TSC2007_12BIT | TSC2007_ADC_ON_IRQ_DIS0)
#define READ_Y      (ADC_ON_12BIT | TSC2007_MEASURE_Y)
#define READ_Z1     (ADC_ON_12BIT | TSC2007_MEASURE_Z1)
#define READ_Z2     (ADC_ON_12BIT | TSC2007_MEASURE_Z2)
#define READ_X      (ADC_ON_12BIT | TSC2007_MEASURE_X)
#define PWRDOWN     (TSC2007_12BIT | TSC2007_POWER_OFF_IRQ_EN)
struct ts_event {
    u16 x;
    u16 y;
    u16 z1, z2;
};
struct tsc2007 {
    struct input_dev    *input;
    char            phys[32];
    struct delayed_work work;
    struct i2c_client   *client;
    u16         model;
    u16         x_plate_ohms;
    bool            pendown;
    int         irq;
    int         (*get_pendown_state)(void);
    void            (*clear_penirq)(void);
};
static inline int tsc2007_xfer(struct tsc2007 *tsc, u8 cmd)
{
    s32 data;
    u16 val;
    data = i2c_smbus_read_word_data(tsc->client, cmd);
    if (data < 0) {
        dev_err(&tsc->client->dev, "i2c io error: %d/n", data);
        return data;
    }
    /* The protocol and raw data format from i2c interface:
     * S Addr Wr [A] Comm [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P
     * Where DataLow has [D11-D4], DataHigh has [D3-D0 << 4 | Dummy 4bit].
     */
    val = swab16(data) >> 4;
    dev_dbg(&tsc->client->dev, "data: 0x%x, val: 0x%x/n", data, val);
    return val;
}
static void tsc2007_read_values(struct tsc2007 *tsc, struct ts_event *tc)
{
    /* y- still on; turn on only y+ (and ADC) */
    tc->y = tsc2007_xfer(tsc, READ_Y);
    /* turn y- off, x+ on, then leave in lowpower */
    tc->x = tsc2007_xfer(tsc, READ_X);
    /* turn y+ off, x- on; we'll use formula #1 */
    tc->z1 = tsc2007_xfer(tsc, READ_Z1);
    tc->z2 = tsc2007_xfer(tsc, READ_Z2);
    /* Prepare for next touch reading - power down ADC, enable PENIRQ */
    tsc2007_xfer(tsc, PWRDOWN);
}
static u32 tsc2007_calculate_pressure(struct tsc2007 *tsc, struct ts_event *tc)
{
    u32 rt = 0;
    /* range filtering */
    if (tc->x == MAX_12BIT)
        tc->x = 0;
    if (likely(tc->x && tc->z1)) {
        /* compute touch pressure resistance using equation #1 */
        rt = tc->z2 - tc->z1;
        rt *= tc->x;
        rt *= tsc->x_plate_ohms;
        rt /= tc->z1;
        rt = (rt + 2047) >> 12;
    }
    return rt;
}
static void tsc2007_send_up_event(struct tsc2007 *tsc)
{
    struct input_dev *input = tsc->input;
    dev_dbg(&tsc->client->dev, "UP/n");
    input_report_key(input, BTN_TOUCH, 0);
    input_report_abs(input, ABS_PRESSURE, 0);
    input_sync(input);
}
//中断后跑到这里来
static void tsc2007_work(struct work_struct *work)
{
    struct tsc2007 *ts =
        container_of(to_delayed_work(work), struct tsc2007, work);
    struct ts_event tc;
    u32 rt;
    /*
     * NOTE: We can't rely on the pressure to determine the pen down
     * state, even though this controller has a pressure sensor.
     * The pressure value can fluctuate for quite a while after
     * lifting the pen and in some cases may not even settle at the
     * expected value.
     *
     * The only safe way to check for the pen up condition is in the
     * work function by reading the pen signal state (it's a GPIO
     * and IRQ). Unfortunately such callback is not always available,
     * in that case we have rely on the pressure anyway.
     */
    if (ts->get_pendown_state) {
        if (unlikely(!ts->get_pendown_state())) {
            tsc2007_send_up_event(ts);
            ts->pendown = false;
            goto out;
        }
        dev_dbg(&ts->client->dev, "pen is still down/n");
    }
    tsc2007_read_values(ts, &tc);
    rt = tsc2007_calculate_pressure(ts, &tc); //计算压力
    if (rt > MAX_12BIT) {
        /*
         * Sample found inconsistent by debouncing or pressure is
         * beyond the maximum. Don't report it to user space,
         * repeat at least once more the measurement.
         */
        dev_dbg(&ts->client->dev, "ignored pressure %d/n", rt);
        goto out;
    }
    if (rt) {
        struct input_dev *input = ts->input;
        if (!ts->pendown) {
            dev_dbg(&ts->client->dev, "DOWN/n");
            input_report_key(input, BTN_TOUCH, 1);
            ts->pendown = true;
        }
        input_report_abs(input, ABS_X, tc.x);
        input_report_abs(input, ABS_Y, tc.y);
        input_report_abs(input, ABS_PRESSURE, rt);
        input_sync(input);
        dev_dbg(&ts->client->dev, "point(%4d,%4d), pressure (%4u)/n",
            tc.x, tc.y, rt);
    } else if (!ts->get_pendown_state && ts->pendown) {
        /*
         * We don't have callback to check pendown state, so we
         * have to assume that since pressure reported is 0 the
         * pen was lifted up.
         */
        tsc2007_send_up_event(ts);
        ts->pendown = false;
    }
 out:
    if (ts->pendown)
        schedule_delayed_work(&ts->work,
                      msecs_to_jiffies(TS_POLL_PERIOD));
    else
        enable_irq(ts->irq);
}
static irqreturn_t tsc2007_irq(int irq, void *handle)
{
    struct tsc2007 *ts = handle;
    if (!ts->get_pendown_state || likely(ts->get_pendown_state())) {
        disable_irq_nosync(ts->irq);
        schedule_delayed_work(&ts->work,
                      msecs_to_jiffies(TS_POLL_DELAY));
    }
    if (ts->clear_penirq)
        ts->clear_penirq();
    return IRQ_HANDLED;
}
static void tsc2007_free_irq(struct tsc2007 *ts)
{
    free_irq(ts->irq, ts);
    if (cancel_delayed_work_sync(&ts->work)) {
        /*
         * Work was pending, therefore we need to enable
         * IRQ here to balance the disable_irq() done in the
         * interrupt handler.
         */
        enable_irq(ts->irq);
    }
}
static int __devinit tsc2007_probe(struct i2c_client *client,
                   const struct i2c_device_id *id)
{
    struct tsc2007 *ts;
    struct tsc2007_platform_data *pdata = pdata = client->dev.platform_data;
    struct input_dev *input_dev;
    int err;
    if (!pdata) {
        dev_err(&client->dev, "platform data is required!/n");
        return -EINVAL;
    }
    if (!i2c_check_functionality(client->adapter,
                     I2C_FUNC_SMBUS_READ_WORD_DATA))
        return -EIO;
    ts = kzalloc(sizeof(struct tsc2007), GFP_KERNEL);
    input_dev = input_allocate_device();
    if (!ts || !input_dev) {
        err = -ENOMEM;
        goto err_free_mem;
    }
    ts->client = client;
    ts->irq = client->irq;
    ts->input = input_dev;
    INIT_DELAYED_WORK(&ts->work, tsc2007_work);
    ts->model             = pdata->model;
    ts->x_plate_ohms      = pdata->x_plate_ohms;
    ts->get_pendown_state = pdata->get_pendown_state;
    ts->clear_penirq      = pdata->clear_penirq;
    snprintf(ts->phys, sizeof(ts->phys),
         "%s/input0", dev_name(&client->dev));
    input_dev->name = "TSC2007 Touchscreen";
    input_dev->phys = ts->phys;
    input_dev->id.bustype = BUS_I2C;
    input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
    input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
    input_set_abs_params(input_dev, ABS_X, 0, MAX_12BIT, 0, 0);
    input_set_abs_params(input_dev, ABS_Y, 0, MAX_12BIT, 0, 0);
    input_set_abs_params(input_dev, ABS_PRESSURE, 0, MAX_12BIT, 0, 0);
    if (pdata->init_platform_hw)
        pdata->init_platform_hw();
    err = request_irq(ts->irq, tsc2007_irq, 0,
            client->dev.driver->name, ts);
    if (err < 0) {
        dev_err(&client->dev, "irq %d busy?/n", ts->irq);
        goto err_free_mem;
    }
    /* Prepare for touch readings - power down ADC and enable PENIRQ */
    err = tsc2007_xfer(ts, PWRDOWN);
    if (err < 0)
        goto err_free_irq;
    err = input_register_device(input_dev);
    if (err)
        goto err_free_irq;
    i2c_set_clientdata(client, ts);
    return 0;
 err_free_irq:
    tsc2007_free_irq(ts);
    if (pdata->exit_platform_hw)
        pdata->exit_platform_hw();
 err_free_mem:
    input_free_device(input_dev);
    kfree(ts);
    return err;
}
static int __devexit tsc2007_remove(struct i2c_client *client)
{
    struct tsc2007  *ts = i2c_get_clientdata(client);
    struct tsc2007_platform_data *pdata = client->dev.platform_data;
    tsc2007_free_irq(ts);
    if (pdata->exit_platform_hw)
        pdata->exit_platform_hw();
    input_unregister_device(ts->input);
    kfree(ts);
    return 0;
}
static struct i2c_device_id tsc2007_idtable[] = {
    { "tsc2007", 0 },
    { }
};
MODULE_DEVICE_TABLE(i2c, tsc2007_idtable);
static struct i2c_driver tsc2007_driver = {
    .driver = {
        .owner  = THIS_MODULE,
        .name   = "tsc2007"
    },
    .id_table   = tsc2007_idtable,
    .probe      = tsc2007_probe,
    .remove     = __devexit_p(tsc2007_remove),
};
static int __init tsc2007_init(void)
{
    return i2c_add_driver(&tsc2007_driver);
}
static void __exit tsc2007_exit(void)
{
    i2c_del_driver(&tsc2007_driver);
}
module_init(tsc2007_init);
module_exit(tsc2007_exit);
MODULE_AUTHOR("Kwangwoo Lee <[e-mail]>");
MODULE_DESCRIPTION("TSC2007 TouchScreen Driver");
MODULE_LICENSE("GPL");

 

看一遍后就大概知道流程了。

当按下触摸板后产生中断，中断里面调用延时函数进入底半部程序。

在调度函数里面，先读取坐标，计算压力，然后根据压力大小上报坐标。

若触摸板一直按下，那么就重新调用，并通过压力值来看触摸板是否释放。

 

简单吧？