// SPDX-License-Identifier: GPL-2.0-only
/* Counter - example userspace application
 *
 * The userspace application opens /dev/counter0, configures the
 * COUNTER_EVENT_INDEX event channel 0 to gather Count 0 count and Count
 * 1 count, and prints out the data as it becomes available on the
 * character device node.
 *
 * Copyright (C) 2021 William Breathitt Gray
 */
#include <errno.h>
#include <fcntl.h>
#include <linux/counter.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>

static struct counter_watch watches[2] = {
        {
                /* Component data: Count 0 count */
                .component.type = COUNTER_COMPONENT_COUNT,
                .component.scope = COUNTER_SCOPE_COUNT,
                .component.parent = 0,
                /* Event type: Index */
                .event = COUNTER_EVENT_INDEX,
                /* Device event channel 0 */
                .channel = 0,
        },
        {
                /* Component data: Count 1 count */
                .component.type = COUNTER_COMPONENT_COUNT,
                .component.scope = COUNTER_SCOPE_COUNT,
                .component.parent = 1,
                /* Event type: Index */
                .event = COUNTER_EVENT_INDEX,
                /* Device event channel 0 */
                .channel = 0,
        },
};

int main(void)
{
        int fd;
        int ret;
        int i;
        struct counter_event event_data[2];

        fd = open("/dev/counter0", O_RDWR);
        if (fd == -1) {
                perror("Unable to open /dev/counter0");
                return 1;
        }

        for (i = 0; i < 2; i++) {
                ret = ioctl(fd, COUNTER_ADD_WATCH_IOCTL, watches + i);
                if (ret == -1) {
                        fprintf(stderr, "Error adding watches[%d]: %s\n", i,
                                strerror(errno));
                        return 1;
                }
        }
        ret = ioctl(fd, COUNTER_ENABLE_EVENTS_IOCTL);
        if (ret == -1) {
                perror("Error enabling events");
                return 1;
        }

        for (;;) {
                ret = read(fd, event_data, sizeof(event_data));
                if (ret == -1) {
                        perror("Failed to read event data");
                        return 1;
                }

                if (ret != sizeof(event_data)) {
                        fprintf(stderr, "Failed to read event data\n");
                        return -EIO;
                }

                printf("Timestamp 0: %llu\tCount 0: %llu\n"
                       "Error Message 0: %s\n"
                       "Timestamp 1: %llu\tCount 1: %llu\n"
                       "Error Message 1: %s\n",
                       event_data[0].timestamp, event_data[0].value,
                       strerror(event_data[0].status),
                       event_data[1].timestamp, event_data[1].value,
                       strerror(event_data[1].status));
        }

        return 0;
}