tools/counter/counter_example.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Counter - example userspace application
   3  *
   4  * The userspace application opens /dev/counter0, configures the
   5  * COUNTER_EVENT_INDEX event channel 0 to gather Count 0 count and Count
   6  * 1 count, and prints out the data as it becomes available on the
   7  * character device node.
   8  *
   9  * Copyright (C) 2021 William Breathitt Gray
  10  */
  11 #include <errno.h>
  12 #include <fcntl.h>
  13 #include <linux/counter.h>
  14 #include <stdio.h>
  15 #include <string.h>
  16 #include <sys/ioctl.h>
  17 #include <unistd.h>
  18
  19 static struct counter_watch watches[2] = {
  20         {
  21                 /* Component data: Count 0 count */
  22                 .component.type = COUNTER_COMPONENT_COUNT,
  23                 .component.scope = COUNTER_SCOPE_COUNT,
  24                 .component.parent = 0,
  25                 /* Event type: Index */
  26                 .event = COUNTER_EVENT_INDEX,
  27                 /* Device event channel 0 */
  28                 .channel = 0,
  29         },
  30         {
  31                 /* Component data: Count 1 count */
  32                 .component.type = COUNTER_COMPONENT_COUNT,
  33                 .component.scope = COUNTER_SCOPE_COUNT,
  34                 .component.parent = 1,
  35                 /* Event type: Index */
  36                 .event = COUNTER_EVENT_INDEX,
  37                 /* Device event channel 0 */
  38                 .channel = 0,
  39         },
  40 };
  41
  42 int main(void)
  43 {
  44         int fd;
  45         int ret;
  46         int i;
  47         struct counter_event event_data[2];
  48
  49         fd = open("/dev/counter0", O_RDWR);
  50         if (fd == -1) {
  51                 perror("Unable to open /dev/counter0");
  52                 return 1;
  53         }
  54
  55         for (i = 0; i < 2; i++) {
  56                 ret = ioctl(fd, COUNTER_ADD_WATCH_IOCTL, watches + i);
  57                 if (ret == -1) {
  58                         fprintf(stderr, "Error adding watches[%d]: %s\n", i,
  59                                 strerror(errno));
  60                         return 1;
  61                 }
  62         }
  63         ret = ioctl(fd, COUNTER_ENABLE_EVENTS_IOCTL);
  64         if (ret == -1) {
  65                 perror("Error enabling events");
  66                 return 1;
  67         }
  68
  69         for (;;) {
  70                 ret = read(fd, event_data, sizeof(event_data));
  71                 if (ret == -1) {
  72                         perror("Failed to read event data");
  73                         return 1;
  74                 }
  75
  76                 if (ret != sizeof(event_data)) {
  77                         fprintf(stderr, "Failed to read event data\n");
  78                         return -EIO;
  79                 }
  80
  81                 printf("Timestamp 0: %llu\tCount 0: %llu\n"
  82                        "Error Message 0: %s\n"
  83                        "Timestamp 1: %llu\tCount 1: %llu\n"
  84                        "Error Message 1: %s\n",
  85                        event_data[0].timestamp, event_data[0].value,
  86                        strerror(event_data[0].status),
  87                        event_data[1].timestamp, event_data[1].value,
  88                        strerror(event_data[1].status));
  89         }
  90
  91         return 0;
  92 }