Linux Platform驅動模型(三) _platform+cdev

平臺匯流排是一種實現設備信息與驅動方法相分離的方法，利用這種方法，我們可以寫出一個更像樣一點的字元設備驅動，即使用cdev作為介面，平臺匯流排作為分離方式:

xjkeydrv_init()：模塊載入函數
└──platform_driver_register()將驅動對象模塊註冊到平臺匯流排
        └──platform_driver.probe()探測函數，提取相應的信息
                └──xjkey_init()：初始化cdev對象，創建設備文件等關於cdev介面創建的工作
                        └──cdev_init():將cdev結構與fops綁定到一起，在fops實現操作介面與控制硬體的邏輯

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;
}

//打開設備
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);
}

//關閉設備
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");