来自用户空间的 sysfs 文件上的 poll() 和来自内核空间的 sysfs_notify() 无法同时工作

Question

我的 raspi 内核模块是为了获得双光栅而编写的，如果两个输入 gpio\xc2\xb4s 边缘中的每一个都上升并且发生中断，则读取单调时间。时间值通过普通的 sysfs 文件传递​​到用户空间（而不是开发文件）。这很好用。

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我的用户空间实现应该读取这些值并计算物体通过光栅的最终速度。目前，这个问题可以通过定期读取 sysfs 文件来解决。如果值发生变化，则会选取并使用新值。

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为了节省资源，我想 poll() 相关 sysfs 文件上的 POLLPRI。在内核模块内部，sysfs_notify() 应该向用户空间提供相关 sysfs 文件的更改状态和值。

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但是我在用户空间中的 poll() 永久阻塞。我也尝试将 POLLIN 作为事件。结果是 poll() 函数立即返回。

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这是我的代码...

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// [...]\n\nstatic struct kobject *gpio; // dir /sys/kernel/gpio\n\nstatic ssize_t gpio17s_show(struct kobject *kobj,struct kobj_attribute\n            *attr,char *buf)\n{\n    return sprintf(buf,"%li",sec1);\n}\n\nstatic ssize_t gpio17s_store(struct kobject *kobj,struct kobj_attribute\n            *attr,const char *buf,size_t count)\n{\n    sscanf(buf,"%li",&sec1);\n    return count;\n}\n\n}\n\n// [...] (two more files)\n\nstatic ssize_t gpio26n_show(struct kobject *kobj,struct kobj_attribute\n            *attr,char *buf)\n{\n    sysfs_notify(gpio,NULL,"gpio26n"); // Is this the right place, the right invocation????\n    // I saw this already in isr, but i believe this is not a good idea....\n    // Has it perhaps to be in module_init function???\n    // First arg(\'gpio\') is kobject of the dir containing files(attributes)..\n    // This can not be right in my mind, but how do I find the right kobj??\n    // The third param \'gpio26n\' if the file, on which I\'m polling.\n\n    return sprintf(buf,"%li",nsec2);\n}\n\nstatic ssize_t gpio26n_store(struct kobject *kobj,struct kobj_attribute\n            *attr,const char *buf,size_t count)\n{\n    sscanf(buf,"%li",&nsec2);\n    return count;\n}\n\nstatic int cleanup(int value,int ret) {\n\n    switch(value) {\n        case 5:\n            free_irq(speed_irq2,NULL);\n        case 4:\n            free_irq(speed_irq1,NULL);\n        case 3:\n            gpio_free(PIN2);\n        case 2:\n            gpio_free(PIN1);\n        case 1:\n            kobject_put(gpio);\n    }\n\n    return ret;\n}\n\nstatic irqreturn_t speed_isr(int irq, void *data) {\n\n    if(irq==speed_irq1) {\n        getrawmonotonic(&ts1);\n        sec1=ts1.tv_sec;\n        nsec1=ts1.tv_nsec;\n    }\n\n    if(irq==speed_irq2) {\n        getrawmonotonic(&ts2);\n        sec2=ts2.tv_sec;\n        nsec2=ts2.tv_nsec;\n    }\n\n    return IRQ_HANDLED;\n}\n\nstatic struct kobj_attribute gpio17s_attr = __ATTR(gpio17s,0644,\n        gpio17s_show,gpio17s_store);\nstatic struct kobj_attribute gpio26n_attr = __ATTR(gpio26n,0644,\n        gpio26n_show,gpio26n_store);\n\nstatic int  __init d_init(void) {\n\n    int ret=0;\n\n    printk(KERN_INFO "Module successfully loaded...");\n\n    gpio=kobject_create_and_add("gpio",kernel_kobj);\n    if(!gpio) {\n        printk(KERN_ERR "Failed to create \'gpio\'");\n        return -ENOMEM;\n    }\n\n    ret=sysfs_create_file(gpio,&gpio17s_attr.attr);\n    if(ret) {\n        printk(KERN_ERR "Failed to create file \'gpio17s\'");\n        return cleanup(1,2);\n    }\n\n    // [...] (two more files)\n\n    ret=sysfs_create_file(gpio,&gpio26n_attr.attr);\n    if(ret) {\n        printk(KERN_ERR "Failed to create file \'gpio26n\'");\n        return cleanup(1,5);\n    }\n\n    ret=gpio_request(PIN1,"gpio 17");\n    if(ret) {\n        printk(KERN_ERR "Failed to request \'gpio17\'");\n        return cleanup(1,6);\n    }\n\n    ret=gpio_request(PIN2,"gpio 26");\n    if(ret) {\n        printk(KERN_ERR "Failed to request \'gpio26\'");\n        return cleanup(2,7);\n    }\n\n    ret=gpio_to_irq(PIN1);\n    if(ret<0) {\n        printk(KERN_ERR "Unable to get irq for pin 17");\n        return cleanup(3,8);\n    }\n\n    speed_irq1=ret;\n\n    ret=gpio_to_irq(PIN2);\n    if(ret<0) {\n        printk(KERN_ERR "Unable to get irq for pin 26");\n        return cleanup(3,9);\n    }\n\n    speed_irq2=ret;\n\n    ret=request_irq(speed_irq1,speed_isr,IRQF_TRIGGER_RISING,\n            "Speed trigger 17",NULL);\n    if(ret) {\n        printk(KERN_ERR "Unable to request irq for pin 17");\n        return cleanup(3,10);\n    }\n\n    ret=request_irq(speed_irq2,speed_isr,IRQF_TRIGGER_RISING,\n            "Speed trigger 26",NULL);\n    if(ret) {\n        printk(KERN_ERR "Unable to request irq for pin 26");\n        return cleanup(4,10);\n    }\n\n    return 0;\n}\n\nstatic void __exit d_exit(void) {\n// [...]\n

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和我的用户空间应用程序

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// [...]\n\nint main() {\n\n    int           f      ;\n    char          buf[16];\n    struct pollfd pfd    ;\n\n    while(1) {\n        memset(buf,0,sizeof(buf));\n\n        if((f=open("/sys/kernel/gpio/gpio26n",O_RDONLY)) <0) {\n            fprintf(stderr,"Failed to open sysfs file\\n");\n            exit(1);\n        }\n\n        if((lseek(f,0L,SEEK_SET)) <0) {\n            fprintf(stderr,"Failed to set pointer\\n");\n            exit(2);\n        }\n\n\n        if((read(f,buf,1)) <0) {\n            fprintf(stderr,"Failed to read from file\\n");\n            exit(3);\n        }\n\n        pfd.fd     = f      ;\n        pfd.events = POLLPRI;\n\n        poll(&pfd,1,-1); // This should block until value has changed....\n        close(f);\n\n\n        // fopen, read new value etc.\n        // [...]\n\n        // Do some stuff, calculate speed, etc\n    }\n}\n

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问候普福

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Answer 1

我放置 sysfs_notify() 函数是错误的。

在这种情况下，正确的位置是 ISR 内。

当中断发生时，ISR 被调用并通过 sysfs_notify() 通知用户空间新数据可读。poll() 解除阻塞并获取数据。

在我之前的星座中，用户空间 poll() 被阻止，直到调用 kobj_attribute show 函数。但只有从文件中读取数据时才会调用此函数。这意味着用户空间应用程序正在等待内核模块和签证 verce。

现在它工作正常。

这是我编辑的代码：

// [...]

static struct kobject *gpio; // dir /sys/kernel/gpio

static ssize_t gpio17s_show(struct kobject *kobj,struct kobj_attribute
            *attr,char *buf)
{
    return sprintf(buf,"%li",sec1);
}

static ssize_t gpio17s_store(struct kobject *kobj,struct kobj_attribute
            *attr,const char *buf,size_t count)
{
    sscanf(buf,"%li",&sec1);
    return count;
}

}

// [...] (two more files)

static ssize_t gpio26n_show(struct kobject *kobj,struct kobj_attribute
            *attr,char *buf)
{
    return sprintf(buf,"%li",nsec2);
}

static ssize_t gpio26n_store(struct kobject *kobj,struct kobj_attribute
            *attr,const char *buf,size_t count)
{
    sscanf(buf,"%li",&nsec2);
    return count;
}

static int cleanup(int value,int ret) {

    switch(value) {
        case 5:
            free_irq(speed_irq2,NULL);
        case 4:
            free_irq(speed_irq1,NULL);
        case 3:
            gpio_free(PIN2);
        case 2:
            gpio_free(PIN1);
        case 1:
            kobject_put(gpio);
    }

    return ret;
}

static irqreturn_t speed_isr(int irq, void *data) {

    if(irq==speed_irq1) {
        getrawmonotonic(&ts1);
        sec1=ts1.tv_sec;
        nsec1=ts1.tv_nsec;
    }

    if(irq==speed_irq2) {
        getrawmonotonic(&ts2);
        sec2=ts2.tv_sec;
        nsec2=ts2.tv_nsec;

        sysfs_notify(gpio,NULL,"gpio26n"); // !! HERE IS THE RIGHT PLACE !!
    }

    return IRQ_HANDLED;
}

static struct kobj_attribute gpio17s_attr = __ATTR(gpio17s,0644,
        gpio17s_show,gpio17s_store);
static struct kobj_attribute gpio26n_attr = __ATTR(gpio26n,0644,
        gpio26n_show,gpio26n_store);

static int  __init d_init(void) {

    int ret=0;

    printk(KERN_INFO "Module successfully loaded...");

    gpio=kobject_create_and_add("gpio",kernel_kobj);
    if(!gpio) {
        printk(KERN_ERR "Failed to create 'gpio'");
        return -ENOMEM;
    }

    ret=sysfs_create_file(gpio,&gpio17s_attr.attr);
    if(ret) {
        printk(KERN_ERR "Failed to create file 'gpio17s'");
        return cleanup(1,2);
    }

    // [...] (two more files)

    ret=sysfs_create_file(gpio,&gpio26n_attr.attr);
    if(ret) {
        printk(KERN_ERR "Failed to create file 'gpio26n'");
        return cleanup(1,5);
    }

    ret=gpio_request(PIN1,"gpio 17");
    if(ret) {
        printk(KERN_ERR "Failed to request 'gpio17'");
        return cleanup(1,6);
    }

    ret=gpio_request(PIN2,"gpio 26");
    if(ret) {
        printk(KERN_ERR "Failed to request 'gpio26'");
        return cleanup(2,7);
    }

    ret=gpio_to_irq(PIN1);
    if(ret<0) {
        printk(KERN_ERR "Unable to get irq for pin 17");
        return cleanup(3,8);
    }

    speed_irq1=ret;

    ret=gpio_to_irq(PIN2);
    if(ret<0) {
        printk(KERN_ERR "Unable to get irq for pin 26");
        return cleanup(3,9);
    }

    speed_irq2=ret;

    ret=request_irq(speed_irq1,speed_isr,IRQF_TRIGGER_RISING,
            "Speed trigger 17",NULL);
    if(ret) {
        printk(KERN_ERR "Unable to request irq for pin 17");
        return cleanup(3,10);
    }

    ret=request_irq(speed_irq2,speed_isr,IRQF_TRIGGER_RISING,
            "Speed trigger 26",NULL);
    if(ret) {
        printk(KERN_ERR "Unable to request irq for pin 26");
        return cleanup(4,10);
    }

    return 0;
}

static void __exit d_exit(void) {
// [...]

问候普福