linux触摸屏驱动分析，touchscreen, struct input_dev,基于TSC2007

代码从2.6.32拷贝：

 /*
  * drivers/input/touchscreen/tsc2007.c
  *
  * Copyright (c) 2008 MtekVision Co., Ltd.
  *  Kwangwoo Lee <[email protected]>
  *
  * 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 <linux/module.h>
 #include <linux/slab.h>
 #include <linux/input.h>
 #include <linux/interrupt.h>
 #include <linux/i2c.h>
 #include <linux/i2c/tsc2007.h>
 #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 <[email protected]>");
 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。