linux字符设备驱动之plat_button

#include "s3c_driver.h"

#define DRV_AUTHOR                "maxiaomi                  <1476759011@qq.com>"
#define DRV_DESC                  "S3C24XX button driver"

/* Driver version*/
#define DRV_MAJOR_VER             1
#define DRV_MINOR_VER             0
#define DRV_REVER_VER             0

#define DEV_NAME                  DEV_BUTTON_NAME

//#define DEV_MAJOR               DEV_BUTTON_MAJOR
#ifndef DEV_MAJOR
#define DEV_MAJOR                 0 /* dynamic major by default */
#endif

#define BUTTON_UP                 0 /* Button status is up */
#define BUTTON_DOWN               1 /* Button status is pushed down */
#define BUTTON_UNCERTAIN          2 /* Button status uncerntain */

#define TIMER_DELAY_DOWN          (HZ/50)   /*Remove button push down dithering timer delay 20ms  */
#define TIMER_DELAY_UP            (HZ/10)   /*Remove button up dithering timer delay 100ms  */

static int debug = DISABLE;
static int dev_major = DEV_MAJOR;
static int dev_minor = 0;

/*============================ Platform Device part ===============================*/
/* Button hardware informtation structure*/
struct s3c_button_info
{
unsigned char           num;       /*Button nubmer  */
char *                  name;      /*Button nubmer  */
int                     nIRQ;      /*Button IRQ number*/
unsigned int            setting;   /*Button IRQ Pin Setting*/
unsigned int            gpio;      /*Button GPIO port */
};

/* The button plaotform device private data structure */
struct s3c_button_platform_data
{
struct s3c_button_info *buttons;
int                     nbuttons;
};

/* Button hardware informtation data*/
static struct s3c_button_info  s3c_buttons[] = {
[0] = {
.num = 1,
.name = "KEY1",
.nIRQ = IRQ_EINT0,
.gpio = S3C2410_GPF(0),
.setting = S3C2410_GPF0_EINT0,
},
[1] = {
.num = 2,
.name = "KEY2",
.nIRQ = IRQ_EINT2,
.gpio = S3C2410_GPF(2),
.setting = S3C2410_GPF2_EINT2,
},
[2] = {
.num = 3,
.name = "KEY3",
.nIRQ = IRQ_EINT3,
.gpio = S3C2410_GPF(3),
.setting = S3C2410_GPF3_EINT3,
},
[3] = {
.num = 4,
.name = "KEY4",
.nIRQ = IRQ_EINT4,
.gpio = S3C2410_GPF(4),
.setting = S3C2410_GPF4_EINT4,
},
};

/* The button platform device private data */
static struct s3c_button_platform_data s3c_button_data = {
.buttons = s3c_buttons,
.nbuttons = ARRAY_SIZE(s3c_buttons),
};

struct button_device
{
unsigned char                      *status;      /* The buttons Push down or up status */
struct s3c_button_platform_data    *data;        /* The buttons hardware information data */

struct timer_list                  *timers;      /* The buttons remove dithering timers */
wait_queue_head_t                  waitq;           /* Wait queue for poll()  */
volatile int                       ev_press;     /* Button pressed event */

struct cdev                        cdev;
struct class                       *dev_class;
} button_device;

static void platform_button_release(struct device * dev)
{
return;
}

static struct platform_device s3c_button_device = {
.name    = "s3c_button",
.id      = 1,
.dev     =
{
.platform_data = &s3c_button_data,
.release = platform_button_release,
},
};

static irqreturn_t s3c_button_intterupt(int irq,void *de_id)
{
int i;
int found = 0;
struct s3c_button_platform_data *pdata = button_device.data;

for(i=0; i<pdata->nbuttons; i++)
{
if(irq == pdata->buttons[i].nIRQ)
{
found = 1;
break;
}                                                              //找出是哪个按键的中断
}

if(!found) /* An ERROR interrupt  */
return IRQ_NONE;

/* Only when button is up then we will handle this event */
if(BUTTON_UP  == button_device.status[i])
{
button_device.status[i] = BUTTON_UNCERTAIN;                    // 设置当前按键的状态为不确定
mod_timer(&(button_device.timers[i]), jiffies+TIMER_DELAY_DOWN);  /*按下按键后开始延时，延时20ms后（抖动期过后），仍然检测为按下，
就说明真的按下，并且只按下一次。那么就进入按键程序了*/
}

return IRQ_HANDLED;
}

static void button_timer_handler(unsigned long data)
{
struct s3c_button_platform_data *pdata = button_device.data;
int num =(int)data;
int status = s3c2410_gpio_getpin( pdata->buttons[num].gpio );

if(LOWLEVEL == status)
{
if(BUTTON_UNCERTAIN == button_device.status[num]) /* Come from interrupt */
{
//dbg_print("Key pressed!\n");
button_device.status[num] = BUTTON_DOWN;

printk("%s pressed.\n", pdata->buttons[num].name);

/* Wake up the wait queue for read()/poll() */
button_device.ev_press = 1;               //设置ev_press为1，如果ev_press为0，则进程进入休眠状态，为1则响应中断，唤醒等待队列让设备进行读取。
wake_up_interruptible(&(button_device.waitq));
}

/* Cancel the dithering  */
mod_timer(&(button_device.timers[num]), jiffies+TIMER_DELAY_UP);
}
else
{
//dbg_print("Key Released!\n");
button_device.status[num] = BUTTON_UP;
//   enable_irq(pdata->buttons[num].nIRQ);
}

return ;
}

/*===================== Button device driver part ===========================*/

static int button_open(struct inode *inode, struct file *file)
{
struct button_device *pdev ;
struct s3c_button_platform_data *pdata;
int i, result;

pdev = container_of(inode->i_cdev,struct button_device, cdev);
pdata = pdev->data;
file->private_data = pdev;

/* Malloc for all the buttons remove dithering timer */
pdev->timers = (struct timer_list *) kmalloc(pdata->nbuttons*sizeof(struct timer_list), GFP_KERNEL);
if(NULL == pdev->timers)
{
printk("Alloc %s driver for timers failure.\n", DEV_NAME);
return -ENOMEM;
}
memset(pdev->timers, 0, pdata->nbuttons*sizeof(struct timer_list));

/* Malloc for all the buttons status buffer */
pdev->status = (unsigned char *)kmalloc(pdata->nbuttons*sizeof(unsigned char), GFP_KERNEL);
if(NULL == pdev->status)
{
printk("Alloc %s driver for status failure.\n", DEV_NAME);
result = -ENOMEM;
goto  ERROR;
}
memset(pdev->status, 0, pdata->nbuttons*sizeof(unsigned char));

init_waitqueue_head(&(pdev->waitq));

for(i=0; i<pdata->nbuttons; i++)
{
/* Initialize all the buttons status to UP  */
pdev->status[i] = BUTTON_UP;

/* Initialize all the buttons' remove dithering timer */
setup_timer(&(pdev->timers[i]), button_timer_handler, i);

/* Set all the buttons GPIO to EDGE_FALLING interrupt mode */
s3c2410_gpio_cfgpin(pdata->buttons[i].gpio, pdata->buttons[i].setting);    //配置成终端模式  ，下降沿触发。
irq_set_irq_type(pdata->buttons[i].nIRQ, IRQ_TYPE_EDGE_FALLING);

/* Request for button GPIO pin interrupt  */
result = request_irq(pdata->buttons[i].nIRQ, s3c_button_intterupt, IRQF_DISABLED, DEV_NAME, (void *)i);   //linux内核中用于申请中断的函数
//一旦发生nIRQ中断号的中断时 ，调用s3c_button_intterupt中断处理程序。
if( result )
{
result = -EBUSY;
goto ERROR1;
}
}

return 0;

ERROR1:
kfree((unsigned char *)pdev->status);
while(--i)
{
disable_irq(pdata->buttons[i].nIRQ);
free_irq(pdata->buttons[i].nIRQ, (void *)i);
}

ERROR:
kfree(pdev->timers);

return result;
}

static int button_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
struct button_device *pdev = file->private_data;
struct s3c_button_platform_data *pdata;
int   i, ret;
unsigned int status = 0;

pdata = pdev->data;

dbg_print("ev_press: %d\n", pdev->ev_press);
if(!pdev->ev_press)
{
if(file->f_flags & O_NONBLOCK)
{
dbg_print("read() without block mode.\n");
return -EAGAIN;
}
else                                                  //使用阻塞模式，等待ev_press为1.
{
/* Read() will be blocked here */
dbg_print("read() blocked here now.\n");
wait_event_interruptible(pdev->waitq, pdev->ev_press);
}
}

pdev->ev_press = 0;

for(i=0; i<pdata->nbuttons; i++)
{
dbg_print("button[%d] status=%d\n", i, pdev->status[i]);
status |= (pdev->status[i]<<i);                        //  确定是哪个按键按下
}

ret = copy_to_user(buf, (void *)&status, min(sizeof(status), count));  //强制类型转换status的地址为(void *)

/*由于内核空间与用户空间的内存不能直接互访，因此借助函数copy_to_user()完成将内核空间的数据到用户空间的复制，
函数copy_from_user()完成将用户空间数据到内核空间的复制。
函数原型：unsigned long copy_to_user(void __user *to, const void *from, unsigned long n);
如果数据拷贝成功，则返回零；否则，返回没有拷贝成功的数据字节数。
*to是用户空间的指针，
*from是内核空间指针，
n表示从内核空间向用户空间拷贝数据的字节数*/

return ret ? -EFAULT : min(sizeof(status), count);
}

static unsigned int button_poll(struct file *file, poll_table * wait)  //多路复用

{
struct button_device *pdev = file->private_data;
unsigned int mask = 0;

poll_wait(file, &(pdev->waitq), wait);
if(pdev->ev_press)
{
mask |= POLLIN | POLLRDNORM; /* The data aviable */
}

return mask;
}
/*其实上面这个函数个人理解是给用户空间提供一个轮询的功能，非阻塞访问则用到了poll机制，不过poll函数将有2个功能函数，首先是poll_wait将这个进程加入到等待队列中，
因为如果你要唤醒它就必须要找到一个地方去等待队列去唤醒它，另一个是do_poll函数，它会帮你一遍遍去查询这个按键是否按下，有则跳出查询，没有则重新加入等待队列，
里面设置了timeout,timeout：是poll函数调用阻塞的时间，单位：毫秒；poll()函数会阻塞timeout所指定的毫秒时间长度之后返回，如果timeout==0，那么poll() 函数立即返回而不阻塞，
如果timeout==INFTIM，那么poll() 函数会一直阻塞下去，直到所检测的有按键按下的事件发生是才返回*/

/*Ps:这里补充一下用户空间select的用法:
使用select函数的过程一般是：
先调用宏FD_ZERO将指定的fd_set清零，然后调用宏FD_SET将需要测试的fd加入fd_set，
接着调用函数select测试fd_set中的所有fd，最后用宏FD_ISSET检查某个fd在函数select调用后，相应位是否仍然为1。

理解select模型的关键在于理解fd_set,为说明方便，取fd_set长度为1字节，fd_set中的每一bit可以对应一个文件描述符fd。则1字节长的fd_set最大可以对应8个fd。
（1）执行fd_set set; FD_ZERO(&set);则set用位表示是0000,0000。
（2）若fd＝5,执行FD_SET(fd,&set);后set变为0001,0000(第5位置为1)
（3）若再加入fd＝2，fd=1,则set变为0001,0011
（4）执行select(6,&set,0,0,0)阻塞等待
（5）若fd=1,fd=2上都发生可读事件，则select返回，此时set变为0000,0011。注意：没有事件发生的fd=5被清空。

*/
static int button_release(struct inode *inode, struct file *file)
{
int i;
struct button_device *pdev = file->private_data;
struct s3c_button_platform_data *pdata;
pdata = pdev->data;

for(i=0; i<pdata->nbuttons; i++)
{
disable_irq(pdata->buttons[i].nIRQ);
free_irq(pdata->buttons[i].nIRQ, (void *)i);
del_timer(&(pdev->timers[i]));
}

kfree(pdev->timers);
kfree((unsigned char *)pdev->status);

return 0;
}

static struct file_operations button_fops = {
.owner = THIS_MODULE,
.open = button_open,
.read = button_read,
.poll = button_poll,
.release = button_release,
};

static int s3c_button_probe(struct platform_device *dev)
{
int result = 0;
dev_t devno;

/* Alloc the device for driver  */
if (0 != dev_major)
{
devno = MKDEV(dev_major, dev_minor);
result = register_chrdev_region(devno, 1, DEV_NAME);
}
else
{
result = alloc_chrdev_region(&devno, dev_minor, 1, DEV_NAME);
dev_major = MAJOR(devno);
}

/* Alloc for device major failure */
if (result < 0)
{
printk("%s driver can't get major %d\n", DEV_NAME, dev_major);
return result;
}

/*  Initialize button_device structure and register cdev*/
memset(&button_device, 0, sizeof(button_device));
button_device.data = dev->dev.platform_data;
cdev_init (&(button_device.cdev), &button_fops);
button_device.cdev.owner  = THIS_MODULE;

result = cdev_add (&(button_device.cdev), devno , 1);
if (result)
{
printk (KERN_NOTICE "error %d add %s device", result, DEV_NAME);
goto ERROR;
}

button_device.dev_class = class_create(THIS_MODULE, DEV_NAME);
if(IS_ERR(button_device.dev_class))
{
printk("%s driver create class failture\n",DEV_NAME);
result =  -ENOMEM;
goto ERROR;
}

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,24)
device_create(button_device.dev_class, NULL, devno, NULL, DEV_NAME);
#else
device_create (button_device.dev_class, NULL, devno, DEV_NAME);
#endif

printk("S3C %s driver version %d.%d.%d initiliazed.\n", DEV_NAME, DRV_MAJOR_VER, DRV_MINOR_VER, DRV_REVER_VER);

return 0;

ERROR:
printk("S3C %s driver version %d.%d.%d install failure.\n", DEV_NAME, DRV_MAJOR_VER, DRV_MINOR_VER, DRV_REVER_VER);
cdev_del(&(button_device.cdev));
unregister_chrdev_region(devno, 1);
return result;
}

static int s3c_button_remove(struct platform_device *dev)
{
dev_t devno = MKDEV(dev_major, dev_minor);

cdev_del(&(button_device.cdev));
device_destroy(button_device.dev_class, devno);
class_destroy(button_device.dev_class);

unregister_chrdev_region(devno, 1);
printk("S3C %s driver removed\n", DEV_NAME);

return 0;
}

/*===================== Platform Device and driver regist part ===========================*/

static struct platform_driver s3c_button_driver = {
.probe      = s3c_button_probe,
.remove     = s3c_button_remove,
.driver     = {
.name       = "s3c_button",
.owner      = THIS_MODULE,
},
};

static int __init s3c_button_init(void)
{
int       ret = 0;

ret = platform_device_register(&s3c_button_device);
if(ret)
{
printk(KERN_ERR "%s: Can't register platform device %d\n", __FUNCTION__, ret);
goto fail_reg_plat_dev;
}
dbg_print("Regist S3C %s Device successfully.\n", DEV_NAME);

ret = platform_driver_register(&s3c_button_driver);
if(ret)
{
printk(KERN_ERR "%s: Can't register platform driver %d\n", __FUNCTION__, ret);
goto fail_reg_plat_drv;
}
dbg_print("Regist S3C %s Driver successfully.\n", DEV_NAME);

return 0;

fail_reg_plat_drv:
platform_driver_unregister(&s3c_button_driver);
fail_reg_plat_dev:
return ret;
}

static void s3c_button_exit(void)
{
platform_driver_unregister(&s3c_button_driver);
dbg_print("S3C %s platform device removed.\n", DEV_NAME);

platform_device_unregister(&s3c_button_device);
dbg_print("S3C %s platform driver removed.\n", DEV_NAME);
}

module_init(s3c_button_init);
module_exit(s3c_button_exit);

module_param(debug, int, S_IRUGO);
module_param(dev_major, int, S_IRUGO);
module_param(dev_minor, int, S_IRUGO);

MODULE_AUTHOR(DRV_AUTHOR);
MODULE_DESCRIPTION(DRV_DESC);
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:S3C24XX_button");