/*
 https://linuxlink.timesys.com/docs/wiki/engineering/HOWTO_Test_RTC_Drivers

 *      Real Time Clock Driver Test/Example Program
 *
 *      Compile with:
 *                     gcc -s -Wall -Wstrict-prototypes rtctest.c -o rtctest
 *
 *      Copyright (C) 1996, Paul Gortmaker.
 *
 *      Released under the GNU General Public License, version 2,
 *      included herein by reference.
 *
 */
#include <stdio.h>
#include <linux/rtc.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
/*
 * This expects the new RTC class driver framework, working with
 * clocks that will often not be clones of what the PC-AT had.
 * Use the command line to specify another RTC if you need one.
 */
static const char default_rtc[] = "/dev/rtc0";
int main(int argc, char **argv)
{
        int i, fd, retval, irqcount = 0;
        unsigned long tmp, data;
        struct rtc_time rtc_tm;
        const char *rtc = default_rtc;
        switch (argc) {
        case 2:
                rtc = argv[1];
                /* FALLTHROUGH */
        case 1:
                break;
        default:
                fprintf(stderr, "usage:  rtctest [rtcdev]\n");
                return 1;
        }
        fd = open(rtc, O_RDONLY);
        if (fd ==  -1) {
                perror(rtc);
                exit(errno);
        }
        fprintf(stderr, "\n\t\t\tRTC Driver Test Example.\n\n");
        /* Turn on update interrupts (one per second) */
        retval = ioctl(fd, RTC_UIE_ON, 0);
        if (retval == -1) {
                if (errno == ENOTTY) {
                        fprintf(stderr,
                                "\n...Update IRQs not supported.\n");
                        goto test_READ;
                }
                perror("RTC_UIE_ON ioctl");
                exit(errno);
        }
        fprintf(stderr, "Counting 5 update (1/sec) interrupts from reading %s:",
                        rtc);
        fflush(stderr);
        for (i=1; i<6; i++) {
                /* This read will block */
                retval = read(fd, &data, sizeof(unsigned long));
                if (retval == -1) {
                        perror("read");
                        exit(errno);
                }
                fprintf(stderr, " %d",i);
                fflush(stderr);
                irqcount++;
        }
        fprintf(stderr, "\nAgain, from using select(2) on /dev/rtc:");
        fflush(stderr);
        for (i=1; i<6; i++) {
                struct timeval tv = {5, 0};     /* 5 second timeout on select */
                fd_set readfds;
                FD_ZERO(&readfds);
                FD_SET(fd, &readfds);
                /* The select will wait until an RTC interrupt happens. */
                retval = select(fd+1, &readfds, NULL, NULL, &tv);
                if (retval == -1) {
                        perror("select");
                        exit(errno);
                }
                /* This read won't block unlike the select-less case above. */
                retval = read(fd, &data, sizeof(unsigned long));
                if (retval == -1) {
                        perror("read");
                        exit(errno);
                }
                fprintf(stderr, " %d",i);
                fflush(stderr);
                irqcount++;
        }
        /* Turn off update interrupts */
        retval = ioctl(fd, RTC_UIE_OFF, 0);
        if (retval == -1) {
                perror("RTC_UIE_OFF ioctl");
                exit(errno);
        }
test_READ:
        /* Read the RTC time/date */
        retval = ioctl(fd, RTC_RD_TIME, &rtc_tm);
        if (retval == -1) {
                perror("RTC_RD_TIME ioctl");
                exit(errno);
        }
        fprintf(stderr, "\n\nCurrent RTC date/time is %d-%d-%d, %02d:%02d:%02d.\n",
                rtc_tm.tm_mday, rtc_tm.tm_mon + 1, rtc_tm.tm_year + 1900,
                rtc_tm.tm_hour, rtc_tm.tm_min, rtc_tm.tm_sec);
        /* Set the alarm to 5 sec in the future, and check for rollover */
        rtc_tm.tm_sec += 5;
        if (rtc_tm.tm_sec >= 60) {
                rtc_tm.tm_sec %= 60;
                rtc_tm.tm_min++;
        }
        if  (rtc_tm.tm_min == 60) {
                rtc_tm.tm_min = 0;
                rtc_tm.tm_hour++;
        }
        if  (rtc_tm.tm_hour == 24)
                rtc_tm.tm_hour = 0;
        retval = ioctl(fd, RTC_ALM_SET, &rtc_tm);
        if (retval == -1) {
                if (errno == ENOTTY) {
                        fprintf(stderr,
                                "\n...Alarm IRQs not supported.\n");
                        goto test_PIE;
                }
                perror("RTC_ALM_SET ioctl");
                exit(errno);
        }
        /* Read the current alarm settings */
        retval = ioctl(fd, RTC_ALM_READ, &rtc_tm);
        if (retval == -1) {
                perror("RTC_ALM_READ ioctl");
                exit(errno);
        }
        fprintf(stderr, "Alarm time now set to %02d:%02d:%02d.\n",
                rtc_tm.tm_hour, rtc_tm.tm_min, rtc_tm.tm_sec);
        /* Enable alarm interrupts */
        retval = ioctl(fd, RTC_AIE_ON, 0);
        if (retval == -1) {
                perror("RTC_AIE_ON ioctl");
                exit(errno);
        }
        fprintf(stderr, "Waiting 5 seconds for alarm...");
        fflush(stderr);
        /* This blocks until the alarm ring causes an interrupt */
        retval = read(fd, &data, sizeof(unsigned long));
        if (retval == -1) {
                perror("read");
                exit(errno);
        }
        irqcount++;
        fprintf(stderr, " okay. Alarm rang.\n");
        /* Disable alarm interrupts */
        retval = ioctl(fd, RTC_AIE_OFF, 0);
        if (retval == -1) {
                perror("RTC_AIE_OFF ioctl");
                exit(errno);
        }
test_PIE:
        /* Read periodic IRQ rate */
        retval = ioctl(fd, RTC_IRQP_READ, &tmp);
        if (retval == -1) {
                /* not all RTCs support periodic IRQs */
                if (errno == ENOTTY) {
                        fprintf(stderr, "\nNo periodic IRQ support\n");
                        goto done;
                }
                perror("RTC_IRQP_READ ioctl");
                exit(errno);
        }
        fprintf(stderr, "\nPeriodic IRQ rate is %ldHz.\n", tmp);
        fprintf(stderr, "Counting 20 interrupts at:");
        fflush(stderr);
        /* The frequencies 128Hz, 256Hz, ... 8192Hz are only allowed for root. */
        for (tmp=2; tmp<=64; tmp*=2) {
                retval = ioctl(fd, RTC_IRQP_SET, tmp);
                if (retval == -1) {
                        /* not all RTCs can change their periodic IRQ rate */
                        if (errno == ENOTTY) {
                                fprintf(stderr,
                                        "\n...Periodic IRQ rate is fixed\n");
                                goto done;
                        }
                        perror("RTC_IRQP_SET ioctl");
                        exit(errno);
                }
                fprintf(stderr, "\n%ldHz:\t", tmp);
                fflush(stderr);
                /* Enable periodic interrupts */
                retval = ioctl(fd, RTC_PIE_ON, 0);
                if (retval == -1) {
                        perror("RTC_PIE_ON ioctl");
                        exit(errno);
                }
                for (i=1; i<21; i++) {
                        /* This blocks */
                        retval = read(fd, &data, sizeof(unsigned long));
                        if (retval == -1) {
                                       perror("read");
                                       exit(errno);
                        }
                        fprintf(stderr, " %d",i);
                        fflush(stderr);
                        irqcount++;
                }
                /* Disable periodic interrupts */
                retval = ioctl(fd, RTC_PIE_OFF, 0);
                if (retval == -1) {
                        perror("RTC_PIE_OFF ioctl");
                        exit(errno);
                }
        }
done:
        fprintf(stderr, "\n\n\t\t\t *** Test complete ***\n");
        close(fd);
        return 0;
}