如何在linux

Question

我尝试在linux中使用GPIO Interrut（下降沿）。（使用GPIO Expander PCAL6524）。

首先，我将GPIO设置为low_active / direction，如下所示。

static int pcal6524_setup(struct i2c_client *client, int gpio,
                unsigned int ngpio, void *context)
{
    int status;
    unsigned char i;
    char label[15];

    gpio += INPUT_BASE;
    for (i = 0; i < 8; ++i) {
        snprintf(label, 10, "exp_input%d", i);
        status = gpio_request(gpio, label);
        if (status)
            goto out_free;
        exp_gpio[i] = gpio++;

        status = gpio_direction_input(exp_gpio[i]);
        if (status) {
            gpio_free(exp_gpio[i]);
            exp_gpio[i] = -EINVAL;
            goto out_free;
        }

        status = gpio_export(exp_gpio[i], 1);
        if (status) {
            gpio_free(exp_gpio[i]);
            exp_gpio[i] = -EINVAL;
            goto out_free;
        }

        status = gpio_sysfs_set_active_low(exp_gpio[i], 1);
        if (status < 0) {
            gpio_free(exp_gpio[i]);
            exp_gpio[i] = -EINVAL;
            goto out_free;
        }
    }

    return status;

out_free:
    for (i = 0; i < 4; ++i) {
        if (exp_gpio[i] != -EINVAL) {
            gpio_free(exp_gpio[i]);
            exp_gpio[i] = -EINVAL;
        }
    }
    return status;
}

我检查了GPIO是否设置在＆＃34; / sys / class / gpio / gpioN＆＃34; - active_low：1，direction：in

但现在我不知道如何设置GPIO下降沿。 我尝试在JNI中设置GPIO下降沿，如下所示。 但是发生了开放错误。（/ sys / class / gpio / gpioN / edge）

/****************************************************************
 * gpio_set_edge
 ****************************************************************/
#define GPIO_PATH "/sys/class/gpio"

int gpio_set_edge(unsigned int gpio, char *edge)
{
    int fd, len;
    char buf[MAX_BUF];

    len = snprintf(buf, sizeof(buf), GPIO_PATH "/gpio%d/edge", gpio);

    fd = open(buf, O_WRONLY);
    if (fd < 0) {
        perror("gpio/set-edge");
        return fd;
    }

    write(fd, edge, strlen(edge) + 1); 
    close(fd);
    return 0;
}

以下是检查和继续GPIO下降沿中断的主程序。

/****************************************************************
 * Main
 ****************************************************************/
int main(int argc, char **argv, char **envp)
{
    struct pollfd fdset[2];
    int nfds = 2;
    int gpio_fd, timeout, rc;
    char *buf[MAX_BUF];
    unsigned int gpio;
    int len;



    if (argc < 2) {
        printf("Usage: gpio-int <gpio-pin>\n\n");
        printf("Waits for a change in the GPIO pin voltage level or input on stdin\n");
        exit(-1);
    }

    gpio = atoi(argv[1]);

    gpio_set_edge(gpio, "rising");
    gpio_fd = gpio_fd_open(gpio);

    timeout = POLL_TIMEOUT;

    while (1) {
        memset((void*)fdset, 0, sizeof(fdset));

        fdset[0].fd = STDIN_FILENO;
        fdset[0].events = POLLIN;

        fdset[1].fd = gpio_fd;
        fdset[1].events = POLLPRI;

        rc = poll(fdset, nfds, timeout);      

        if (rc < 0) {
            printf("\npoll() failed!\n");
            return -1;
        }

        if (rc == 0) {
            printf(".");
        }

        if (fdset[1].revents & POLLPRI) {
            lseek(fdset[1].fd, 0, SEEK_SET);
            len = read(fdset[1].fd, buf, MAX_BUF);
            printf("\npoll() GPIO %d interrupt occurred\n", gpio);
        }

        if (fdset[0].revents & POLLIN) {
            (void)read(fdset[0].fd, buf, 1);
            printf("\npoll() stdin read 0x%2.2X\n", (unsigned int) buf[0]);
        }

        fflush(stdout);
    }

    gpio_fd_close(gpio_fd);
    return 0;
}

我找到了为什么发生了开放错误.. 当我检查gpio的文件属性时，我发现gpio的读/写权限如下。

  

130 | shell @ test_ref：/ sys / class / gpio / gpio218 $ ll   -rw-r - r-- root root 4096 2009-09-01 01:56 active_low

     

lrwxrwxrwx root root 2009-09-01 01:56 device - ＆gt;   ../../../ 0-0022

     

-rw-r - r-- root root 4096 2009-09-01 01:56方向

     

-rw-r - r-- root root 4096 2009-09-01 00:30 edge

     

drwxr-xr-x root root 2009-09-01 00:00 power

     

lrwxrwxrwx root root 2009-09-01 01:56子系统 - ＆gt;   ../../../../../../../类/ GPIO

     

-rw-r - r-- root root 4096 2009-09-01 00:00 uevent

     

-rw-r - r-- root root 4096 2009-09-01 00:00 value

如上所述，gpio / edge的写入权限已被拒绝......

如何在linux内核中允许gpio / edge的写权限？

由于