mini2440 平台上挂载I2C接口触摸屏的驱动开发过程

本篇记录在友善之臂 mini2440 平台上挂载I2C接口触摸屏的驱动开发过程。

内核版本linux-2.6.32.2,

平台是ARM9 S3C2440+I2C接口的触摸屏

如上篇Linux的I2C驱动体系结构讲述
http://www.lupaworld.com/273398/viewspace-204237.html
要挂载新的I2C设备，需要实现3部分：

1) 适配器的硬件驱动：

内核中已经实现mini2440,i2c适配器驱动，可以在如下目录i2c-s3c2410.c中看到相关代码

linux-2.6.32.2/drivers/i2c/busses/i2c-s3c2410.c

2) I2C 设配器的algorithm

同样在inux-2.6.32.2/drivers/i2c/busses/i2c-s3c2410.c文件中实现。

以上两部分无须做任何更改

3) I2C设备驱动，可以以linux-2.6.32.2/drivers/input/touchscreen/migor_ts.c为例，分析如下：

//-------------------------------------------------------------------//

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/input.h>

#include <linux/interrupt.h>

#include <asm/io.h>

#include <linux/i2c.h>

#include <linux/timer.h>

#include <linux/delay.h>

/*resolution definion according to touch screen */

#define MIN_X_COORDINATE 0

#define MAX_X_COORDINATE 1024

#define MIN_Y_COORDINATE 0

#define MAX_Y_COORDINATE 768

/* touch screen data structure */

struct i2c_ts_priv {

struct i2c_client *client;

struct input_dev *input;

struct delayed_work work;

int irq;

};

static void i2c_ts_poscheck(struct work_struct *work)

{

struct i2c_ts_priv *priv = container_of(work, struct i2c_ts_priv, work.work);

/* buffer for storing data */

char buf[6];

int number;

int xpos, ypos;

memset(buf, 0, sizeof(buf));

/* Now do Page Read */

if (i2c_master_recv(priv->client, buf,6) != 6) {

dev_err(&priv->client->dev, "Unable to read i2c page\n");

goto out;

}

/* convert coordinate */

number = buf[0]&0x07;

xpos = ((buf[3] << 8) | buf[2]);

ypos = ((buf[5] << 8) | buf[4]);

/* report input event */

if ((number != 0) && (xpos != 0) && (ypos != 0)) {

input_report_key(priv->input, BTN_TOUCH, 1);

input_report_abs(priv->input, ABS_X, xpos);

input_report_abs(priv->input, ABS_Y, ypos);

input_sync(priv->input);

} else if (number == 0) {

input_report_key(priv->input, BTN_TOUCH, 0);

input_sync(priv->input);

}

out:

enable_irq(priv->irq);

}

/* read finger numbers and coordinate and report input event */

static irqreturn_t i2c_ts_isr(int irq, void *dev_id)

{

struct i2c_ts_priv *priv = dev_id;

/* disable irq */

disable_irq_nosync(irq);

schedule_delayed_work(&priv->work, HZ/100);

return IRQ_HANDLED;

}

static int i2c_ts_open(struct input_dev *dev)

{

return 0;

}

static void i2c_ts_close(struct input_dev *dev)

{

}

static int i2c_ts_probe(struct i2c_client *client,

const struct i2c_device_id *idp)

{

struct i2c_ts_priv *priv;

struct input_dev *input;

int error;

char buf[2];

priv = kzalloc(sizeof(*priv), GFP_KERNEL);

if (!priv) {

dev_err(&client->dev, "failed to allocate driver data\n");

error = -ENOMEM;

goto err0;

}

dev_set_drvdata(&client->dev, priv);

input = input_allocate_device();

if (!input) {

dev_err(&client->dev, "Failed to allocate input device.\n");

error = -ENOMEM;

goto err1;

}

input->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);

input->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);

input_set_abs_params(input, ABS_X, MIN_X_COORDINATE, MAX_X_COORDINATE, 0, 0);

input_set_abs_params(input, ABS_Y, MIN_Y_COORDINATE, MAX_Y_COORDINATE, 0, 0);

input->name = client->name;

input->id.bustype = BUS_I2C;

input->dev.parent = &client->dev;

input->open = i2c_ts_open;

input->close = i2c_ts_close;

input_set_drvdata(input, priv);

priv->client = client;

priv->input = input;

INIT_DELAYED_WORK(&priv->work, i2c_ts_poscheck);

priv->irq = client->irq;

error = input_register_device(input);

if (error)

goto err1;

error = request_irq(priv->irq, i2c_ts_isr, IRQF_TRIGGER_FALLING,

client->name, priv);

if (error) {

dev_err(&client->dev, "Unable to request touchscreen IRQ.\n");

goto err2;

}

device_init_wakeup(&client->dev,1);

return 0;

err2:

input_unregister_device(input);

input = NULL; /* so we dont try to free it below */

err1:

input_free_device(input);

kfree(priv);

err0:

dev_set_drvdata(&client->dev, NULL);

return error;

}

static int i2c_ts_remove(struct i2c_client *client)

{

struct i2c_ts_priv *priv = dev_get_drvdata(&client->dev);

free_irq(priv->irq, priv);

input_unregister_device(priv->input);

kfree(priv);

dev_set_drvdata(&client->dev, NULL);

return 0;

}

static int i2c_ts_suspend(struct i2c_client *client, pm_message_t mesg)

{

struct i2c_ts_priv *priv = dev_get_drvdata(&client->dev);

if(device_may_wakeup(&client->dev))

enable_irq_wake(priv->irq);

return 0;

}

static int i2c_ts_resume(struct i2c_client *client)

{

struct i2c_ts_priv *priv = dev_get_drvdata(&client->dev);

if(device_may_wakeup(&client->dev))

disable_irq_wake(priv->irq);

return 0;

}

static const struct i2c_device_id i2c_ts_id[] = {

{ "i2c-ts", 0 },

{ }

};

MODULE_DEVICE_TABLE(i2c, i2c_ts_id);

static struct i2c_driver i2c_ts_driver = {

.driver = {

.name = "i2c-ts",

},

.probe = i2c_ts_probe,

.remove = i2c_ts_remove,

.suspend = i2c_ts_suspend,

.resume = i2c_ts_resume,

.id_table = i2c_ts_id,

};

static int __init i2c_ts_init(void)

{

return i2c_add_driver(&i2c_ts_driver);

}

static void __exit i2c_ts_exit(void)

{

i2c_del_driver(&i2c_ts_driver);

}

MODULE_DESCRIPTION("i2c Touchscreen driver");

MODULE_AUTHOR("ALlen <allen.p.wang@gmail.com>");

MODULE_LICENSE("GPL");

module_init(i2c_ts_init);

module_exit(i2c_ts_exit);

4).实现如上步骤后，还需要创建和配置I2C 设备,设置文件位于

linux-2.6.32.2/arch/arm/mach-s3c2440/mach-mini2440.c中，

添加如下代码：

..................................................

+/* I2C touch screen devices. */

+/* bus configuration */

+static struct s3c2410_platform_i2c i2c_touchscreen_cfg __initdata = {

+ .flags = 0,

+ .slave_addr = 0x5c,

+ .frequency = 100*1000,

+ .sda_delay = 2,

+};

+/* i2c device name is "i2c_ts", address is 0x5c, interrupt is eint20 */

+static struct i2c_board_info touchscreen_i2c_devs[] __initdata = {

+ {

+ I2C_BOARD_INFO("i2c-ts", 0x5c),

+ .irq = IRQ_EINT20,

+ },

+};

...................................................

static void __init mini2440_machine_init(void)

{

..................................................

+ /* i2c touch screen devices */

+ s3c_i2c0_set_platdata(&i2c_touchscreen_cfg);

+ i2c_register_board_info(0, touchscreen_i2c_devs, +ARRAY_SIZE(touchscreen_i2c_devs));

...................................................

}

此处I2C_BOARD_INFO("i2c-ts",0x5c), “i2c-ts” 要和i2c设备驱动中i2c_ts_id一致。

才能保证i2c设备驱动成功加载。