d7bcdca7a9
On 32 bit platforms, a PHC driver might allow a larger adjustment than can fit into the 'long' type used in the clock_adjtime interface. This patch fixes the issue by using the smaller of the two maxima. Signed-off-by: Richard Cochran <richardcochran@gmail.com>
71 lines
1.8 KiB
C
71 lines
1.8 KiB
C
/**
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* @file phc.c
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* @note Copyright (C) 2011 Richard Cochran <richardcochran@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <stdio.h>
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#include <sys/ioctl.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <linux/ptp_clock.h>
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#include "phc.h"
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/*
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* On 32 bit platforms, the PHC driver's maximum adjustment (type
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* 'int' in units of ppb) can overflow the timex.freq field (type
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* 'long'). So in this case we clamp the maximum to the largest
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* possible adjustment that fits into a 32 bit long.
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*/
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#define BITS_PER_LONG (sizeof(long)*8)
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#define MAX_PPB_32 32767999 /* 2^31 - 1 / 65.536 */
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clockid_t phc_open(char *phc)
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{
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int fd = open(phc, O_RDWR);
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return fd < 0 ? CLOCK_INVALID : FD_TO_CLOCKID(fd);
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}
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void phc_close(clockid_t clkid)
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{
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if (clkid == CLOCK_INVALID)
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return;
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close(CLOCKID_TO_FD(clkid));
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}
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int phc_max_adj(clockid_t clkid)
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{
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int fd = CLOCKID_TO_FD(clkid), max;
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struct ptp_clock_caps caps;
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if (ioctl(fd, PTP_CLOCK_GETCAPS, &caps)) {
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perror("PTP_CLOCK_GETCAPS");
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return 0;
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}
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max = caps.max_adj;
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if (BITS_PER_LONG == 32 && max > MAX_PPB_32)
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max = MAX_PPB_32;
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return max;
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}
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