Linux的I2C 设备驱动 -- mini2440 上i2c接口触摸屏驱动
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。
