osx - kevent & USB serial ports -


i'm having trouble using kevent on mac usb serial console. i've narrowed down to:

#include <errno.h>                                                                                                                                           #include <fcntl.h> #include <stdio.h> #include <string.h> #include <sys/event.h> #include <sys/ioctl.h> #include <termios.h>  #define device "/dev/cu.usbserial-0011111d"  int main() {   int kqueue_fd = kqueue();   if (kqueue_fd < 0) {     printf("failed open kqueue\n");     return -1;   }   int device_fd = open(device, o_rdwr | o_nonblock | o_noctty);   if (device_fd < 0) {     printf("failed open device: %s\n", device);     return -1;   }   printf("opened %d\n", device_fd);    enum { max_events = 1 };   struct kevent events[max_events];    ev_set(&events[0], device_fd, evfilt_read, ev_add, 0, 0, null);    int r = kevent(kqueue_fd, events, 1, null, 0, null);   if (r < 0) {     printf("kevent failed: %s\n", strerror(errno));     return -1;   }    struct timespec sleep_time;   sleep_time.tv_sec = 5;   sleep_time.tv_nsec = 0;    int ready = kevent(kqueue_fd, null, 0, (struct kevent*) &events,                      max_events, &sleep_time);   if (ready == 0) {     printf("no event\n");     return 0;   }   (int = 0; < ready; i++) {     printf(".ident %ld, .filter %d, .flags 0x%x, .fflags 0x%x, "            ".data: %ld, .udata %p\n",            events[i].ident,            events[i].filter,            events[i].flags,            events[i].fflags,            events[i].data,            events[i].udata);      int unread = 0;     r = ioctl(events[i].ident, fionread, &unread);     if (r < 0) {       printf("ioctl failed: %d: %s\n", errno, strerror(errno));     }   } }

when run , unplug usb device in middle of call kevent(), get:

opened 4 .ident 4, .filter -1, .flags 0x1, .fflags 0x0, .data: 6, .udata 0x0 ioctl failed: 6: device not configured

my understanding contents of event translates to:

fd 4, evfilt_read, ev_add, 6 bytes remaining on fd. ioctl() fails (since device removed), , errno 6, seems if event.data returning errno, not bytes remaining.

how can differentiate between normal read case , case device has been removed? filter, flags & fflags appear same in both cases.

additional information

if switch opening serial console pipe, , write single byte followed closing write end, get:

pipe() fd: 5 -> 4 .ident 4, .filter -1, .flags 0x1, .fflags 0x0, .data: 1, .udata 0x0 .ident 4, .filter -1, .flags 0x8001, .fflags 0x0, .data: 0, .udata 0x0

this expect, since 0x8000 ev_eof.


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