Linux Platform驱动模型(三) _platform+cdev

平台总线是一种实现设备信息与驱动方法相分离的方法，利用这种方法，我们可以写出一个更像样一点的字符设备驱动，即使用cdev作为接口，平台总线作为分离方式:

xjkeydrv_init()：模块加载函数
└──platform_driver_register()将驱动对象模块注册到平台总线
└──platform_driver.probe()探测函数，提取相应的信息
└──xjkey_init()：初始化cdev对象，创建设备文件等关于cdev接口创建的工作
└──cdev_init():将cdev结构与fops绑定到一起，在fops实现操作接口与控制硬件的逻辑

static struct class *cls = NULL;

static int major = 0;
static int minor = 0;
const  int count = 1;

#define DEVNAME	"xjkey"

static struct cdev *xjkeyp = NULL;

static unsigned long irqflags;
static int irq;

static atomic_t tv;

#if 0
/{
	key@26{
		compatible = "xj4412,key";
		interrupt-parent = <&gpx1>;
		interrupts = <2 2>;
	};
};
#endif

static irqreturn_t handler_t(int irq, void *dev_id)
{
	printk(KERN_INFO "%s : %s : %d\n", __FILE__, __func__, __LINE__);
	return IRQ_HANDLED;
}

//打开设备
static int xjkey_open(struct inode *inode, struct file *filp)
{
	//get major and minor from inode
	printk(KERN_INFO "(major=%d, minor=%d), %s : %s : %d\n",
		imajor(inode), iminor(inode), __FILE__, __func__, __LINE__);

	if(!atomic_dec_and_test(&tv)){
		atomic_inc(&tv);
		return -EBUSY;
	}

	return request_irq(irq, handler_t, irqflags, DEVNAME, NULL);
}

//关闭设备
static int xjkey_release(struct inode *inode, struct file *filp)
{
	//get major and minor from irqflagsinode
	printk(KERN_INFO "(major=%d, minor=%d), %s : %s : %d\n",
		imajor(inode), iminor(inode), __FILE__, __func__, __LINE__);

	free_irq(irq, NULL);

	atomic_inc(&tv);
	return 0;
}

static struct file_operations fops = {
	.owner	= THIS_MODULE,
	.open	= xjkey_open,
	.release= xjkey_release,
};

static int xjkey_init(void)
{
	dev_t devnum;
	int ret, i;

	struct device *devp = NULL;

	//get command and pid
	printk(KERN_INFO "(%s:pid=%d), %s : %s : %d\n",
		current->comm, current->pid, __FILE__, __func__, __LINE__);

	//1. alloc cdev objxjkey_init
	xjkeyp = cdev_alloc();
	if(NULL == xjkeyp){
		return -ENOMEM;
	}

	//2. init cdev obj
	cdev_init(xjkeyp, &fops);

	ret = alloc_chrdev_region(&devnum, minor, count, DEVNAME);
	if(ret){
		goto ERR_STEP;
	}
	major = MAJOR(devnum);

	//3. register cdev obj
	ret = cdev_add(xjkeyp, devnum, count);
	if(ret){
		goto ERR_STEP1;
	}

	cls = class_create(THIS_MODULE, DEVNAME);
	if(IS_ERR(cls)){
		ret = PTR_ERR(cls);
		goto ERR_STEP1;
	}

	for(i = minor; i < (count+minor); i++){
		devp = device_create(cls, NULL, MKDEV(major, i), NULL, "%s%d", DEVNAME, i);
		if(IS_ERR(devp)){
			ret = PTR_ERR(devp);
			goto ERR_STEP2;
		}
	}

	// init atomic_t
	atomic_set(&tv, 1);

	//get command and pid
	printk(KERN_INFO "(%s:pid=%d), %s : %s : %d - ok.\n",
		current->comm, current->pid, __FILE__, __func__, __LINE__);
	return 0;

ERR_STEP2:
	for(--i; i >= minor; i--){
		device_destroy(cls, MKDEV(major, i));
	}
	class_destroy(cls);

ERR_STEP1:
	unregister_chrdev_region(devnum, count);

ERR_STEP:
	cdev_del(xjkeyp);

	//get command and pid
	printk(KERN_INFO "(%s:pid=%d), %s : %s : %d - fail.\n",
		current->comm, current->pid, __FILE__, __func__, __LINE__);
	return ret;
}

static void xjkey_exit(void)
{
	int i;
	//get command and pid
	printk(KERN_INFO "(%s:pid=%d), %s : %s : %d - leave.\n",
		current->comm, current->pid, __FILE__, __func__, __LINE__);

	for(i=minor; i < (count+minor); i++){
		device_destroy(cls, MKDEV(major, i));
	}
	class_destroy(cls);

	unregister_chrdev_region(MKDEV(major, minor), count);
	cdev_del(xjkeyp);
}

static int xjkey_probe(struct platform_device *pdev)
{
	struct resource *irq_res;
	irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
	if(irq_res){
		irq = irq_res->start;
		irqflags = irq_res->flags & IRQF_TRIGGER_MASK;
	}else{
		printk(KERN_INFO "No 0 irq\n");
		return -EINVAL;		
	}

	return xjkey_init();
}

static int xjkey_remove(struct platform_device *pdev)
{
	printk(KERN_INFO "%s : %s : %d - leave.\n", __FILE__, __func__, __LINE__);
	xjkey_exit();
	return 0;
}

struct of_device_id of_tbl[] = {
	{.compatible = "xj4412,key",},
	{},
};
MODULE_DEVICE_TABLE(of, of_tbl);


//1. alloc obj
static struct platform_driver xjkeydrv = {
	.probe	= xjkey_probe,
	.remove	= xjkey_remove,

	.driver = {
		.name = DEVNAME,
		.of_match_table = of_tbl,
	},
};

//3. register obj
module_platform_driver(xjkeydrv);

MODULE_LICENSE("GPL");