/*
 * Copyright (C) 2018 AVM GmbH <fritzbox_info@avm.de>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
#include <stddef.h>
#include <string.h>
#include <errno.h>
#include "wdt.h"
#include "wdt-private.h"

#define ARRAY_SIZE(a)       (sizeof(a)/sizeof(a[0]))
#define MISC_MAJOR          10

static const char *wdt_devicename[] = {
#ifdef USE_AVM_DEVICE_NAMESPACE
    "/dev/avm_watchdog",
#endif
    "/dev/watchdog" /* Fallback device name, shared with mainline watchdog driver */
};

const char *watchdog_device_name(void)
{
    struct stat statbuf;
    unsigned i;
    int ret;

    for (i = 0; i < ARRAY_SIZE(wdt_devicename); ++i) {
        /*
         * The avm watchdog registers its device with a dynamic major id,
         * whereas the standard /dev/watchdog is a misc device.  Assume we're
         * ok if our device is a char device, and not a misc device.
         *
         * We can't open+fstat, since opening the device starts watchdogs
         * with mainline drivers, and that may be a one-way ticket.
         */
        ret = stat(wdt_devicename[i], &statbuf);
        if (ret == 0 && S_ISCHR(statbuf.st_mode) &&
                major(statbuf.st_rdev) != MISC_MAJOR)
            return wdt_devicename[i];
    }

    errno = ENODEV;
    return NULL;
}

int watchdog_open_device(void)
{
    const char *devname;
    int fd;

    devname = watchdog_device_name();
    if (!devname)
        return WDT_UNKNOWN_HANDLE;

    fd = open(devname, O_RDWR);
    if (fd < 0)
        return WDT_ALREADY_REGISTERED;

    return fd;
}