linuxptp/phc.c

88 lines
2.1 KiB
C

/**
* @file phc.c
* @note Copyright (C) 2011 Richard Cochran <richardcochran@gmail.com>
*
* 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.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <stdio.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/ptp_clock.h>
#include "phc.h"
/*
* On 32 bit platforms, the PHC driver's maximum adjustment (type
* 'int' in units of ppb) can overflow the timex.freq field (type
* 'long'). So in this case we clamp the maximum to the largest
* possible adjustment that fits into a 32 bit long.
*/
#define BITS_PER_LONG (sizeof(long)*8)
#define MAX_PPB_32 32767999 /* 2^31 - 1 / 65.536 */
clockid_t phc_open(char *phc)
{
int fd = open(phc, O_RDWR);
return fd < 0 ? CLOCK_INVALID : FD_TO_CLOCKID(fd);
}
void phc_close(clockid_t clkid)
{
if (clkid == CLOCK_INVALID)
return;
close(CLOCKID_TO_FD(clkid));
}
static int phc_get_caps(clockid_t clkid, struct ptp_clock_caps *caps)
{
int fd = CLOCKID_TO_FD(clkid), err;
err = ioctl(fd, PTP_CLOCK_GETCAPS, caps);
if (err)
perror("PTP_CLOCK_GETCAPS");
return err;
}
int phc_max_adj(clockid_t clkid)
{
int max;
struct ptp_clock_caps caps;
if (phc_get_caps(clkid, &caps))
return 0;
max = caps.max_adj;
if (BITS_PER_LONG == 32 && max > MAX_PPB_32)
max = MAX_PPB_32;
return max;
}
int phc_has_pps(clockid_t clkid)
{
struct ptp_clock_caps caps;
if (phc_get_caps(clkid, &caps))
return 0;
return caps.pps;
}