actledPi.c

/*
 * This is free and unencumbered software released into the public domain.
 *
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 *
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * For more information, please refer to <http://unlicense.org/>
 *
 **************************************************************************
 *
 * A disk activity light for the Raspberry Pi.
 * Blinks the ACT led on all mass storage I/O, i.e. not only the SD card. 
 * Based on hddled.c - http://members.optusnet.com.au/foonly/whirlpool/code/hddled.c -
 * 
 *
 * To compile:
 *   gcc -Wall -O3 -o actledPi actledPi.c
 *
 * Options:
 * -d, --detach               Detach from terminal (become a daemon)
 * -r, --refresh=VALUE        Refresh interval (default: 20 ms)
 *
 */


#define VMSTAT "/proc/vmstat"
#define ACTLED "/sys/class/leds/led0/brightness"
#define TRGCTL "/sys/class/leds/led0/trigger"
#define LOW     0
#define HIGH    1

#define _GNU_SOURCE

#include <argp.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

static unsigned int o_refresh = 20; /* milliseconds */
static int o_detach = 0;

static volatile sig_atomic_t running = 1;
static char *line = NULL;
static size_t len = 0;

FILE *actled = NULL;
FILE *trigger_ctl = NULL;

/* Reread the vmstat file */
int activity(FILE *vmstat) {
        static unsigned int prev_pgpgin, prev_pgpgout;
        unsigned int pgpgin, pgpgout;
        int found_pgpgin, found_pgpgout;
        int result;

        /* Reload the vmstat file */
        result = TEMP_FAILURE_RETRY(fseek(vmstat, 0L, SEEK_SET));
        if (result) {
                perror("Could not rewind " VMSTAT);
                return result;
        }

        /* Clear glibc's buffer */
        result = TEMP_FAILURE_RETRY(fflush(vmstat));
        if (result) {
                perror("Could not flush input stream");
                return result;
        }

        /* Extract the I/O stats */
        found_pgpgin = found_pgpgout = 0;
        while (getline(&line, &len, vmstat) != -1 && errno != EINTR) {
                if (sscanf(line, "pgpgin %u", &pgpgin))
                        found_pgpgin++;
                else if (sscanf(line, "pgpgout %u", &pgpgout))
                        found_pgpgout++;
                if (found_pgpgin && found_pgpgout)
                        break;
        }
        if (!found_pgpgin || !found_pgpgout) {
                fprintf(stderr, "Could not find required lines in " VMSTAT);
                return -1;
        }

        /* Anything changed? */
        result =
                (prev_pgpgin  != pgpgin) ||
                (prev_pgpgout != pgpgout);
        prev_pgpgin = pgpgin;
        prev_pgpgout = pgpgout;

        return result;
}

/* Update the LED */
void led(int on) {
        static int current = 1; /* Ensure the LED turns off on first call */
        if (current == on)
                return;

        if (on) {
                fputs("255\n", actled);
        } else {
                fputs("0\n", actled);
        }
        fflush(actled);
        current = on;
}

/* Signal handler -- break out of the main loop */
void shutdown(int sig) {
        running = 0;
}

/* Argp parser function */
error_t parse_options(int key, char *arg, struct argp_state *state) {
        switch (key) {
        case 'd':
                o_detach = 1;
                break;
        case 'r':
                o_refresh = strtol(arg, NULL, 10);
                if (o_refresh < 10)
                        argp_failure(state, EXIT_FAILURE, 0,
                                "refresh interval must be at least 10");
                break;
        }
        return 0;
}

int main(int argc, char **argv) {
        struct argp_option options[] = {
                { "detach",  'd',      NULL, 0, "Detach from terminal" },
                { "refresh", 'r',   "VALUE", 0, "Refresh interval (default: 20 ms)" },
                { 0 },
        };
        struct argp parser = {
                NULL, parse_options, NULL,
                "Show disk activity on all disks.",
                NULL, NULL, NULL
        };
        int status = EXIT_FAILURE;
        FILE *vmstat = NULL;
        struct timespec delay;

        /* Parse the command-line */
        parser.options = options;
        if (argp_parse(&parser, argc, argv, ARGP_NO_ARGS, NULL, NULL))
                goto out;

        delay.tv_sec = o_refresh / 1000;
        delay.tv_nsec = 1000000 * (o_refresh % 1000);


        /* Open the vmstat file */
        vmstat = fopen(VMSTAT, "r");
        if (!vmstat) {
                perror("Could not open " VMSTAT " for reading");
                goto out;
        }

        /* Change the trigger on the OK/Act LED to "none" */

        trigger_ctl = fopen(TRGCTL, "rw");
        if (!trigger_ctl) {
                perror("Unable to change LED trigger");
                goto out;
        }
        fputs ("none\n", trigger_ctl);
        fclose (trigger_ctl);


        /* Open the actled file */
        actled = fopen(ACTLED, "w");
        if (!actled) {
                perror("Could not open " ACTLED " for writing");
                goto out;
        }

        /* Ensure the LED is off */
        led(LOW);

        if (activity(vmstat) < 0)
                goto out;

        /* Detach from terminal? */
        if (o_detach) {
                pid_t child = fork();
                if (child < 0) {
                        perror("Could not detach from terminal");
                        goto out;
                }
                if (child) {
                        /* I am the parent */
                        status = EXIT_SUCCESS;
                        goto out;
                }
        }

        /* We catch these signals so we can clean up */
        {
                struct sigaction action;
                memset(&action, 0, sizeof(action));
                action.sa_handler = shutdown;
                sigemptyset(&action.sa_mask);
                action.sa_flags = 0; /* We block on usleep; don't use SA_RESTART */
                sigaction(SIGHUP, &action, NULL);
                sigaction(SIGINT, &action, NULL);
                sigaction(SIGTERM, &action, NULL);
        }

        /* Loop until signal received */
        while (running) {
                int a;
                if (nanosleep(&delay, NULL) < 0)
                        break;
                a = activity(vmstat);
                if (a < 0)
                        break;
                led(a);
        }

        /* Ensure the LED is off */
        led(LOW);

        status = EXIT_SUCCESS;

out:
        if (line) free(line);
        if (vmstat) fclose(vmstat);
        if (actled) {
                fclose(actled);
                trigger_ctl = fopen(TRGCTL, "rw");
                fputs("mmc0\n", trigger_ctl);
                fclose(trigger_ctl);
        }
        return status;
}