如何获得SD卡的事件通知？(How to get notifications for SD card

2019-06-25 09:36发布

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我要检查SD卡的存在，并收到通知SD卡添加/删除。

到目前为止，我已经使用libudev ，和我做了一个小的应用程序，它侦听SD卡事件。

该代码是下面列出： 

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h>
#include <errno.h>
#include <sys/time.h> //debug -> remove me

#include <libudev.h>

#define ADD_FILTER "add"
#define REMOVE_FILTER "remove"
#define SUBSYSTEM_FILTER "block"
#define ATTR_FILTER "ID_MODEL"
#define SD_ATTR_VALUE "SD_MMC"
#define ATTR_ACTIVE_SD "ID_PART_TABLE_TYPE"

static bool isDeviceSD(struct udev_device *device);
static bool isDevPresent(struct udev *device);
static void print_device(struct udev_device *device, const char *source); //for debugging -> remove me
static bool s_bSD_present;

int main()
{
    struct udev *udev;
    struct udev_monitor *udev_monitor = NULL;
    fd_set readfds;
    s_bSD_present = false;

    udev = udev_new();
    if (udev == NULL)
    {
        printf("udev_new FAILED \n");
        return 1;
    }

    s_bSD_present = isDevPresent(udev);
    if(s_bSD_present)
    {
        printf("+++SD is plugged in \n");
    }
    else
    {
        printf("---SD is not plugged in \n");
    }

    udev_monitor = udev_monitor_new_from_netlink(udev, "udev");
    if (udev_monitor == NULL) {
        printf("udev_monitor_new_from_netlink FAILED \n");
        return 1;
    }

    //add some filters
    if( udev_monitor_filter_add_match_subsystem_devtype(udev_monitor, SUBSYSTEM_FILTER, NULL) < 0 )
    {
        printf("udev_monitor_filter_add_match_subsystem_devtype FAILED \n");
        return 1;
    }

    if (udev_monitor_enable_receiving(udev_monitor) < 0)
    {
        printf("udev_monitor_enable_receiving FAILED \n");
        return 1;
    }

    while (1) {
        printf("Polling for new data... \n");

        int fdcount = 0;

        FD_ZERO(&readfds);

        if (udev_monitor != NULL)
        {
            FD_SET(udev_monitor_get_fd(udev_monitor), &readfds);
        }

        fdcount = select(udev_monitor_get_fd(udev_monitor)+1, &readfds, NULL, NULL, NULL);
        if (fdcount < 0)
        {
            if (errno != EINTR)
                printf("Error receiving uevent message\n");
            continue;
        }

        if ((udev_monitor != NULL) && FD_ISSET(udev_monitor_get_fd(udev_monitor), &readfds))
        {
            struct udev_device *device;

            device = udev_monitor_receive_device(udev_monitor);
            if (device == NULL)
                continue;

            //check the action
            const char* szAction = udev_device_get_action(device);
            if( strcmp(szAction, ADD_FILTER) == 0)
            {
                if( !s_bSD_present && isDeviceSD(device) )
                {
                    s_bSD_present = true;
                    printf("+++SD has been plugged in \n");
                }
            }
            else if( strcmp(szAction, REMOVE_FILTER) == 0 )
            {
                if( s_bSD_present && isDeviceSD(device) )
                {
                    s_bSD_present = false;
                    printf("---SD has been removed \n");
                }
            }

            udev_device_unref(device);
        }
    }

    return 0;
}

static bool isDeviceSD(struct udev_device *device)
{
    bool retVal = false;
    struct udev_list_entry *list_entry = 0;
    struct udev_list_entry* model_entry = 0;
    struct udev_list_entry* active_sd_entry = 0;

    list_entry = udev_device_get_properties_list_entry(device);
    model_entry = udev_list_entry_get_by_name(list_entry, ATTR_FILTER);
    if( 0 != model_entry )
    {
        const char* szModelValue = udev_list_entry_get_value(model_entry);
        active_sd_entry = udev_list_entry_get_by_name(list_entry, ATTR_ACTIVE_SD);
        if(strcmp(szModelValue, SD_ATTR_VALUE) == 0 && active_sd_entry != 0)
        {
            printf("Device is SD \n");
            retVal = true;

            //print_device(device, "UDEV");
        }
    }
    return retVal;
}


static bool isDevPresent(struct udev *device)
{
    bool retVal = false;
    struct udev_enumerate *enumerate;
    struct udev_list_entry *devices, *dev_list_entry;

    enumerate = udev_enumerate_new(device);
    udev_enumerate_add_match_subsystem(enumerate, SUBSYSTEM_FILTER);
    udev_enumerate_scan_devices(enumerate);
    devices = udev_enumerate_get_list_entry(enumerate);

    udev_list_entry_foreach(dev_list_entry, devices)
    {
        struct udev_device *dev;
        const char* dev_path = udev_list_entry_get_name(dev_list_entry);
        dev = udev_device_new_from_syspath(device, dev_path);

        if( true == isDeviceSD(dev) )
        {
            retVal = true;
            udev_device_unref(dev);
            break;
        }

        udev_device_unref(dev);
    }
    udev_enumerate_unref(enumerate);

    return retVal;
}


static void print_device(struct udev_device *device, const char *source)
{
      struct timeval tv;
      struct timezone tz;

      gettimeofday(&tv, &tz);
      printf("%-6s[%llu.%06u] %-8s %s (%s)\n",
             source,
             (unsigned long long) tv.tv_sec, (unsigned int) tv.tv_usec,
             udev_device_get_action(device),
             udev_device_get_devpath(device),
             udev_device_get_subsystem(device));

            struct udev_list_entry *list_entry;

            udev_list_entry_foreach(list_entry, udev_device_get_properties_list_entry(device))
                  printf("%s=%s\n",
                         udev_list_entry_get_name(list_entry),
                         udev_list_entry_get_value(list_entry));
            printf("\n");

}

此代码将获得SD卡的通知添加/删除（和SD的初始状态 - 插入/拔出）。 然而，它更是一个黑客，它不适用于所有情况。

我目前使用的ID_MODEL设备的属性，并检查它是否是SD_MMC -为SD卡。 我只需要这种类型的卡，现在，所以这是不够的。

当SD卡被插入时，以下事件为子系统块发送：2个change事件，和1个add每个分区事件。 事件属性如下： 

<----- change event - subsystem block - disk type disk ----->

UDEV  [1339412734.522055] change   /devices/pci0000:00/0000:00:11.0/0000:02:03.0/usb1/1-1/1-1:1.0/host11/target11:0:0/11:0:0:2/block/sdd (block)
UDEV_LOG=3
ACTION=change
DEVPATH=/devices/pci0000:00/0000:00:11.0/0000:02:03.0/usb1/1-1/1-1:1.0/host11/target11:0:0/11:0:0:2/block/sdd
SUBSYSTEM=block
DEVNAME=/dev/sdd
DEVTYPE=disk
SEQNUM=3168
ID_VENDOR=Generic-
ID_VENDOR_ENC=Generic-
ID_VENDOR_ID=0bda
ID_MODEL=SD_MMC
ID_MODEL_ENC=SD\x2fMMC\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20
ID_MODEL_ID=0151
ID_REVISION=1.00
ID_SERIAL=Generic-_SD_MMC_20060413092100000-0:2
ID_SERIAL_SHORT=20060413092100000
ID_TYPE=disk
ID_INSTANCE=0:2
ID_BUS=usb
ID_USB_INTERFACES=:080650:
ID_USB_INTERFACE_NUM=00
ID_USB_DRIVER=usb-storage
ID_PATH=pci-0000:02:03.0-usb-0:1:1.0-scsi-0:0:0:2
ID_PART_TABLE_TYPE=dos
UDISKS_PRESENTATION_NOPOLICY=0
UDISKS_PARTITION_TABLE=1
UDISKS_PARTITION_TABLE_SCHEME=mbr
UDISKS_PARTITION_TABLE_COUNT=2
MAJOR=8
MINOR=48
DEVLINKS=/dev/block/8:48 /dev/disk/by-id/usb-Generic-_SD_MMC_20060413092100000-0:2 /dev/disk/by-path/pci-0000:02:03.0-usb-0:1:1.0-scsi-0:0:0:2

<----- add event partition 1 - subsystem block - disk type partition ----->

UDEV  [1339412734.719107] add      /devices/pci0000:00/0000:00:11.0/0000:02:03.0/usb1/1-1/1-1:1.0/host11/target11:0:0/11:0:0:2/block/sdd/sdd1 (block)
UDEV_LOG=3
ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:11.0/0000:02:03.0/usb1/1-1/1-1:1.0/host11/target11:0:0/11:0:0:2/block/sdd/sdd1
SUBSYSTEM=block
DEVNAME=/dev/sdd1
DEVTYPE=partition
SEQNUM=3169
ID_VENDOR=Generic-
ID_VENDOR_ENC=Generic-
ID_VENDOR_ID=0bda
ID_MODEL=SD_MMC
ID_MODEL_ENC=SD\x2fMMC\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20
ID_MODEL_ID=0151
ID_REVISION=1.00
ID_SERIAL=Generic-_SD_MMC_20060413092100000-0:2
ID_SERIAL_SHORT=20060413092100000
ID_TYPE=disk
ID_INSTANCE=0:2
ID_BUS=usb
ID_USB_INTERFACES=:080650:
ID_USB_INTERFACE_NUM=00
ID_USB_DRIVER=usb-storage
ID_PATH=pci-0000:02:03.0-usb-0:1:1.0-scsi-0:0:0:2
ID_PART_TABLE_TYPE=dos
ID_FS_UUID=6343c7b9-92a9-4d8f-bdd8-893f1190f294
ID_FS_UUID_ENC=6343c7b9-92a9-4d8f-bdd8-893f1190f294
ID_FS_VERSION=1.0
ID_FS_TYPE=ext2
ID_FS_USAGE=filesystem
UDISKS_PRESENTATION_NOPOLICY=0
UDISKS_PARTITION=1
UDISKS_PARTITION_SCHEME=mbr
UDISKS_PARTITION_NUMBER=1
UDISKS_PARTITION_TYPE=0x83
UDISKS_PARTITION_SIZE=1006919680
UDISKS_PARTITION_SLAVE=/sys/devices/pci0000:00/0000:00:11.0/0000:02:03.0/usb1/1-1/1-1:1.0/host11/target11:0:0/11:0:0:2/block/sdd
UDISKS_PARTITION_OFFSET=11618304
UDISKS_PARTITION_ALIGNMENT_OFFSET=0
MAJOR=8
MINOR=49
DEVLINKS=/dev/block/8:49 /dev/disk/by-id/usb-Generic-_SD_MMC_20060413092100000-0:2-part1 /dev/disk/by-path/pci-0000:02:03.0-usb-0:1:1.0-scsi-0:0:0:2-part1 /dev/disk/by-uuid/6343c7b9-92a9-4d8f-bdd8-893f1190f294

<----- add event partition 2 - subsystem block - disk type partition ----->

UDEV  [1339412734.731338] add      /devices/pci0000:00/0000:00:11.0/0000:02:03.0/usb1/1-1/1-1:1.0/host11/target11:0:0/11:0:0:2/block/sdd/sdd2 (block)
UDEV_LOG=3
ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:11.0/0000:02:03.0/usb1/1-1/1-1:1.0/host11/target11:0:0/11:0:0:2/block/sdd/sdd2
SUBSYSTEM=block
DEVNAME=/dev/sdd2
DEVTYPE=partition
SEQNUM=3170
ID_VENDOR=Generic-
ID_VENDOR_ENC=Generic-
ID_VENDOR_ID=0bda
ID_MODEL=SD_MMC
ID_MODEL_ENC=SD\x2fMMC\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20
ID_MODEL_ID=0151
ID_REVISION=1.00
ID_SERIAL=Generic-_SD_MMC_20060413092100000-0:2
ID_SERIAL_SHORT=20060413092100000
ID_TYPE=disk
ID_INSTANCE=0:2
ID_BUS=usb
ID_USB_INTERFACES=:080650:
ID_USB_INTERFACE_NUM=00
ID_USB_DRIVER=usb-storage
ID_PATH=pci-0000:02:03.0-usb-0:1:1.0-scsi-0:0:0:2
ID_PART_TABLE_TYPE=dos
UDISKS_PRESENTATION_NOPOLICY=0
UDISKS_PARTITION=1
UDISKS_PARTITION_SCHEME=mbr
UDISKS_PARTITION_NUMBER=2
UDISKS_PARTITION_TYPE=0xda
UDISKS_PARTITION_SIZE=11618304
UDISKS_PARTITION_FLAGS=boot
UDISKS_PARTITION_SLAVE=/sys/devices/pci0000:00/0000:00:11.0/0000:02:03.0/usb1/1-1/1-1:1.0/host11/target11:0:0/11:0:0:2/block/sdd
UDISKS_PARTITION_OFFSET=1022410752
UDISKS_PARTITION_ALIGNMENT_OFFSET=0
MAJOR=8
MINOR=50
DEVLINKS=/dev/block/8:50 /dev/disk/by-id/usb-Generic-_SD_MMC_20060413092100000-0:2-part2 /dev/disk/by-path/pci-0000:02:03.0-usb-0:1:1.0-scsi-0:0:0:2-part2

从change情况下，我不能提取关于设备是否被添加或删除的任何信息。 我试图打开设备名称\dev\sdd ，但我没有权限，因此该选项下降...

现在我只是在检查分区的操作属性（ add / remove ）。

此版本的程序非常有效的有分区的SD卡。 当没有分区，只change接收事件。

所以我的问题是 ：有什么办法可以检查是否添加/从删除的媒体change的事件吗？ 或者是有一些其他的方法来检查设备是否可用（记住分区问题保持）？

于提高所述设备属性的迭代或获取通知的方法的任何建议将受到欢迎。

PS我不能使用libusb :)。

Answer 1:

好。 所以，我得到它的工作在PC上的SD卡不分区。

更新后的代码是这样的： 

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h>
#include <errno.h>
#include <sys/time.h> //debug -> remove me
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <libudev.h>

#define ADD_FILTER "add"
#define REMOVE_FILTER "remove"
#define SUBSYSTEM_FILTER "block"
#define DEVTYPE_FILTER "disk"
#define ATTR_FILTER "ID_MODEL"
#define SD_ATTR_VALUE "SD_MMC"
#define ATTR_ADDED_DISK "UDISKS_PARTITION_TABLE" // attribute is available for "change" event when SD card is added (n/a when removed)

static bool isDeviceSD(struct udev_device *device); //checks if device is SD card (MMC)
static bool isDevPresent(struct udev *device); //checks if device is present (SD + added)
static bool isDeviceAdded(struct udev_device *device); //checks if device is added (presence of attribute ATTR_ADDED_DISK)
static void print_device(struct udev_device *device, const char *source); //for debugging -> remove me
static bool s_bSD_present;

int main()
{
    struct udev *udev;
    struct udev_monitor *udev_monitor = NULL;
    fd_set readfds;
    s_bSD_present = false;

    udev = udev_new();
    if (udev == NULL)
    {
        printf("udev_new FAILED \n");
        return 1;
    }

    if( isDevPresent(udev) )
    {
        s_bSD_present = true;
        printf("+++SD is plugged in \n");
    }
    else
    {
        printf("---SD is not plugged in \n");
    }

    udev_monitor = udev_monitor_new_from_netlink(udev, "udev");
    if (udev_monitor == NULL) {
        printf("udev_monitor_new_from_netlink FAILED \n");
        return 1;
    }

    //add some filters
    if( udev_monitor_filter_add_match_subsystem_devtype(udev_monitor, SUBSYSTEM_FILTER, DEVTYPE_FILTER) < 0 )
    {
        printf("udev_monitor_filter_add_match_subsystem_devtype FAILED \n");
        return 1;
    }

    if (udev_monitor_enable_receiving(udev_monitor) < 0)
    {
        printf("udev_monitor_enable_receiving FAILED \n");
        return 1;
    }

    while (1) {
        printf("Polling for new data... \n");

        int fdcount = 0;

        FD_ZERO(&readfds);

        if (udev_monitor != NULL)
        {
            FD_SET(udev_monitor_get_fd(udev_monitor), &readfds);
        }

        fdcount = select(udev_monitor_get_fd(udev_monitor)+1, &readfds, NULL, NULL, NULL);
        if (fdcount < 0)
        {
            if (errno != EINTR)
                printf("Error receiving uevent message\n");
            continue;
        }

        if ((udev_monitor != NULL) && FD_ISSET(udev_monitor_get_fd(udev_monitor), &readfds))
        {
            struct udev_device *device;

            device = udev_monitor_receive_device(udev_monitor);
            if (device == NULL)
                continue;

            //check presence
            if( isDeviceSD(device) && isDeviceAdded(device) )
            {
                if(!s_bSD_present) //guard for double "change" events
                {
                    s_bSD_present = true;
                    printf("+++SD has been plugged in \n");
                }
            }
            else
            {
                if(s_bSD_present) //not needed -> just keeping consistency
                {
                    s_bSD_present = false;
                    printf("---SD has been removed \n");
                }
            }

            udev_device_unref(device);
        }
    }

    return 0;
}

static bool isDeviceSD(struct udev_device *device)
{
    bool retVal = false;
    struct udev_list_entry *list_entry = 0;
    struct udev_list_entry* model_entry = 0;

    list_entry = udev_device_get_properties_list_entry(device);
    model_entry = udev_list_entry_get_by_name(list_entry, ATTR_FILTER);
    if( 0 != model_entry )
    {
        const char* szModelValue = udev_list_entry_get_value(model_entry);
        if( strcmp( szModelValue, SD_ATTR_VALUE) == 0 )
        {
            //printf("Device is SD \n");
            retVal = true;

            //print_device(device, "UDEV");
        }
    }
    return retVal;
}

static bool isDeviceAdded(struct udev_device *device)
{
    bool retVal = false;
    struct udev_list_entry *list_entry = 0;
    struct udev_list_entry* added_disk_entry = 0;


    list_entry = udev_device_get_properties_list_entry(device);
    added_disk_entry = udev_list_entry_get_by_name(list_entry,/* "DEVNAME" */ ATTR_ADDED_DISK);
    if( 0 != added_disk_entry )
    {
        retVal = true;
    }
    return retVal;
}


static bool isDevPresent(struct udev *device)
{
    bool retVal = false;
    struct udev_enumerate *enumerate;
    struct udev_list_entry *devices, *dev_list_entry;

    enumerate = udev_enumerate_new(device);
    udev_enumerate_add_match_subsystem(enumerate, SUBSYSTEM_FILTER);
    udev_enumerate_scan_devices(enumerate);
    devices = udev_enumerate_get_list_entry(enumerate);

    udev_list_entry_foreach(dev_list_entry, devices)
    {
        struct udev_device *dev;
        const char* dev_path = udev_list_entry_get_name(dev_list_entry);
        dev = udev_device_new_from_syspath(device, dev_path);

        if( isDeviceSD(dev) && isDeviceAdded(dev) )
        {
            retVal = true;
            udev_device_unref(dev);
            break;
        }

        udev_device_unref(dev);
    }
    udev_enumerate_unref(enumerate);

    return retVal;
}


static void print_device(struct udev_device *device, const char *source)
{
      struct timeval tv;
      struct timezone tz;

      gettimeofday(&tv, &tz);
      printf("%-6s[%llu.%06u] %-8s %s (%s)\n",
             source,
             (unsigned long long) tv.tv_sec, (unsigned int) tv.tv_usec,
             udev_device_get_action(device),
             udev_device_get_devpath(device),
             udev_device_get_subsystem(device));

            struct udev_list_entry *list_entry;

            udev_list_entry_foreach(list_entry, udev_device_get_properties_list_entry(device))
                  printf("%s=%s\n",
                         udev_list_entry_get_name(list_entry),
                         udev_list_entry_get_value(list_entry));
            printf("\n");

}

该解决方案（仍然不是很亮）正在检查一些属性，只有当SD卡被添加（如可用UDISKS_PARTITION_TABLE ）。

这种运作良好，在x86上。



文章来源: How to get notifications for SD card events?
标签： c linux udev
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