linux 驱动开发问题记录

问题1

ioctl(fd,2,arg): bad address

写了一个字符驱动,使用ioctl控制,内核版本是4.1.15

static struct file_operations spp_fops = {
 	...
 	...
 	
 	.unlocked_ioctl   =       spp_ioctl,	
	.owner            =       THIS_MODULE
};

static long spp_ioctl(struct file *file, unsigned int cmd, unsigned long arg) {  

这个 ioctl cmd 定义为 r=1,write=2;也就是传参的时候 cmd的值为1或者2;
这个时候问题就出现了,测试代码如下

#define readflag        1
#define writeflag       2

        int s32res;
        s32res = ioctl(fd,writeflag,0x55);
        if (s32res<0)
                printf("err:%d,%s \n",s32res,strerror(errno));
                
        s32res = ioctl(fd,readflag,0x0f80<<8);
        if (s32res<0)
                printf("err:%d,%s \n",s32res,strerror(errno));

,在写测试用例的时候,s32res = ioctl(fd,writeflag,0x55);这句,报错.bad address,驱动的spp_ioctl函数都没进去;同样的驱动和测试代码,在3.1.6内核中运行正常

解决

后来我将 spp_ioctl 的cmd参数定义为0和1,绕过2去,没有报错

poll接口

配合中断使用,如果原子量等于0,说明设备没有准备好,将打开这个接口的进程加入一个等待队列中,函数退出后,在sys_poll中,会阻塞调用的进程,等待进程被中断唤醒,或者超时

static unsigned int ddr_fifo_poll(struct file * file, struct poll_table_struct * poll_table)
{
	unsigned int mask = 0;
	struct ddr_fifo_dev * df_devdata = container_of(file->private_data, struct ddr_fifo_dev, miscdev);
	if (atomic_read(&df_devdata->irq_flag)==0) {
		dev_dbg(df_devdata->device, "%s wait\n", __FUNCTION__);
		/*Suspend the process and join the waiting queue,This function exits and waits to be woken up or timed out*/
		poll_wait(file, &df_devdata->r_wait, poll_table);
	}else{
		dev_dbg(df_devdata->device, "%s poll in %d\n", __FUNCTION__,atomic_read(&df_devdata->irq_flag));
		atomic_dec(&df_devdata->irq_flag);
		mask = POLLIN | POLLRDNORM;
	}
	return mask;
}

中断处理接口,这个其实是中断的一个底半部,接收到中断后,原子量+1,

static irqreturn_t irq_interrupt(int irq, void * dev_id)
{
	struct ddr_fifo_dev * df_devdata = (struct ddr_fifo_dev *)dev_id;
	if (df_devdata->file != NULL && df_devdata->async_queue != NULL) {
		kill_fasync(&df_devdata->async_queue, SIGIO, POLL_IN);
	}
	//接收到中断后原子量加一
	atomic_inc(&df_devdata->irq_flag);
	//唤醒等待队列
	wake_up_interruptible(&df_devdata->r_wait);
	dev_dbg(df_devdata->device, "%08X@irq thread  handle,in=%08X flag=%d\n", (u32)df_devdata->physreg,ddr_rxfifo_get_inindex(df_devdata->regbase),atomic_read(&df_devdata->irq_flag));
	return IRQ_HANDLED;
}

中断

中断的几个属性标记的作用
IRQF_ONESHOT: 中断在中断处理函数被调用时不触发,不允许嵌套
IRQF_SHARED:中断号可以共享,一个中断号可以注册多个中断处理函数

#define IRQF_TRIGGER_NONE    0x00000000
#define IRQF_TRIGGER_RISING    0x00000001-----------------------上升沿触发
#define IRQF_TRIGGER_FALLING    0x00000002----------------------下降沿触发
#define IRQF_TRIGGER_HIGH    0x00000004-------------------------高电平触发
#define IRQF_TRIGGER_LOW    0x00000008--------------------------地电平触发
#define IRQF_TRIGGER_MASK    (IRQF_TRIGGER_HIGH | IRQF_TRIGGER_LOW | \
                 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING)--------四种触发类型
#define IRQF_TRIGGER_PROBE    0x00000010
#define IRQF_SHARED        0x00000080---------------------------多个设备共享一个中断号
#define IRQF_PROBE_SHARED    0x00000100-------------------------中断处理程序允许sharing mismatch发生
#define __IRQF_TIMER        0x00000200--------------------------标记一个时钟中断
#define IRQF_PERCPU        0x00000400---------------------------属于某个特定CPU的中断
#define IRQF_NOBALANCING    0x00000800--------------------------禁止在多CPU之间做中断均衡
#define IRQF_IRQPOLL        0x00001000--------------------------中断被用作轮询
#define IRQF_ONESHOT        0x00002000--------------------------一次性触发中断，不允许嵌套。
#define IRQF_NO_SUSPEND        0x00004000-----------------------在系统睡眠过程中不要关闭该中断
#define IRQF_FORCE_RESUME    0x00008000-------------------------在系统唤醒过程中必须抢孩子打开该中断
#define IRQF_NO_THREAD        0x00010000------------------------表示该中断不会给线程化
#define IRQF_EARLY_RESUME    0x00020000
#define IRQF_COND_SUSPEND    0x00040000
#define IRQF_TIMER        (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)