好。因此，我可以在没有分区的SD卡PC上使用它。
更新的代码是这样的：
#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 mestatic 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 messagen"); 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, 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=%sn", udev_list_entry_get_name(list_entry), udev_list_entry_get_value(list_entry)); printf("n");}解决方案（仍然不是很明亮）正在检查某些属性，该属性仅在添加SD卡时才可用（例如
UDISKS_PARTITION_TABLE）。
这在x86上效果很好。
