Hello Noé,
I just submitted a patch on 14-09-27 that adds this functionality
without creating a new state file.
On 10/07/2014 05:15 AM, Noé Rubinstein wrote:
> From: Noé Rubinstein <noe.rubinstein@xxxxxxxxx>
>
> This option is useful for systems that have a working hardware clock, but do
> not provide a way to write to it. Instead of setting the hardware clock, write
> the difference between hardware and system clock to a file; when getting the
> hardware clock, add the offset from this file to obtain the correct time.
>
> I have not checked how well this interacts with the adjtime mechanism, so
> this is an RFC patch.
> ---
> sys-utils/hwclock.8.in | 6 ++++
> sys-utils/hwclock.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 92 insertions(+), 2 deletions(-)
>
> diff --git a/sys-utils/hwclock.8.in b/sys-utils/hwclock.8.in
> index b11b45c..63fabda 100644
> --- a/sys-utils/hwclock.8.in
> +++ b/sys-utils/hwclock.8.in
> @@ -113,6 +113,12 @@ not reset.
> .BR \-w , \ \-\-systohc
> Set the Hardware Clock to the current System Time.
> .TP
> +.BR \-\-offset[=filename]
> +This option is useful for systems that have a working hardware clock, but do
> +not provide a way to write to it. Instead of setting the hardware clock, write
> +the difference between hardware and system clock to a file; when getting the
> +hardware clock, add the offset from this file to obtain the correct time.
> +.TP
> .BR \-V , \ \-\-version
> Display version information and exit.
> .TP
> diff --git a/sys-utils/hwclock.c b/sys-utils/hwclock.c
> index e780158..c7deab9 100644
> --- a/sys-utils/hwclock.c
> +++ b/sys-utils/hwclock.c
> @@ -98,6 +98,7 @@ struct clock_ops *ur;
> #define MAX_DRIFT 2145.0
>
> const char *adj_file_name = NULL;
> +const char *offset_file_name = NULL;
>
> struct adjtime {
> /*
> @@ -234,6 +235,35 @@ hw_clock_is_utc(const bool utc, const bool local_opt,
> return ret;
> }
>
> +static int read_offset(struct timeval *offset)
> +{
> + FILE *f;
> + int rc;
> + f = fopen(offset_file_name, "r");
> + if (!f)
> + return -errno;
> +
> + rc = fread(offset, sizeof(*offset), 1, f);
> + fclose(f);
> +
> + return rc == 1 ? 0 : -EINVAL;
> +}
> +
> +static int write_offset(struct timeval offset)
> +{
> + FILE *f;
> + int rc;
> + f = fopen(offset_file_name, "w");
> + if (!f)
> + return -errno;
> +
> + rc = fwrite(&offset, sizeof(offset), 1, f);
> + fclose(f);
> +
> + return rc == 1 ? 0 : -EINVAL;
> +}
> +
> +
> /*
> * Read the adjustment parameters out of the /etc/adjtime file.
> *
> @@ -1290,6 +1320,8 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
> bool no_auth;
> /* The time at which we read the Hardware Clock */
> struct timeval read_time;
> + /* The offset between system time and hardware time */
> + struct timeval offset = {0};
> /*
> * The Hardware Clock gives us a valid time, or at
> * least something close enough to fool mktime().
> @@ -1320,6 +1352,11 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
> adjtime.dirty = FALSE;
> }
>
> + if ((hctosys || show) && offset_file_name)
> + {
> + read_offset(&offset);
> + }
> +
> universal = hw_clock_is_utc(utc, local_opt, adjtime);
>
> if ((set || systohc || adjust) &&
> @@ -1328,7 +1365,8 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
> adjtime.dirty = TRUE;
> }
>
> - if (show || adjust || hctosys || (!noadjfile && !systz && !predict)) {
> + if (show || adjust || hctosys || (!noadjfile && !systz && !predict) ||
> + offset_file_name) {
> /* data from HW-clock are required */
> rc = synchronize_to_clock_tick();
>
> @@ -1358,8 +1396,20 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
> }
>
> if (show) {
> - display_time(hclock_valid, hclocktime,
> + display_time(hclock_valid, hclocktime + offset.tv_sec,
> time_diff(read_time, startup_time));
> + } else if (set && offset_file_name) {
> + if (!hclock_valid) {
> + printf(_("Hardware clock invalid, not writing offset.\n"));
> + } else {
> + offset.tv_sec = set_time - hclocktime;
> + rc = write_offset(offset);
> + if (rc) {
> + printf(_("Unable to write offset: %s."), strerror(-rc));
> + return rc;
> + }
> + }
> +
> } else if (set) {
> set_hardware_clock_exact(set_time, startup_time,
> universal, testing);
> @@ -1371,6 +1421,18 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
> } else if (adjust) {
> do_adjustment(&adjtime, hclock_valid,
> hclocktime, read_time, universal, testing);
> + } else if (systohc && offset_file_name) {
> + if (!hclock_valid) {
> + printf(_("Hardware clock invalid, not writing offset.\n"));
> + } else {
> + gettimeofday(&offset, NULL);
> + offset.tv_sec -= hclocktime;
> + rc = write_offset(offset);
> + if (rc) {
> + printf(_("Unable to write offset: %s."), strerror(-rc));
> + return rc;
> + }
> + }
> } else if (systohc) {
> struct timeval nowtime, reftime;
> /*
> @@ -1390,6 +1452,17 @@ manipulate_clock(const bool show, const bool adjust, const bool noadjfile,
> reftime.tv_sec,
> hclock_valid, hclocktime, (double)
> read_time.tv_usec / 1E6);
> + } else if (hctosys && offset_file_name) {
> + if (!hclock_valid) {
> + printf(_("Hardware clock invalid, not setting time.\n"));
> + } else {
> + offset.tv_sec += hclocktime;
> + rc = settimeofday(&offset, NULL);
> + if (rc) {
> + printf(_("Unable to set system clock.\n"));
> + return rc;
> + }
> + }
> } else if (hctosys) {
> rc = set_system_clock(hclock_valid, hclocktime, testing);
> if (rc) {
> @@ -1547,6 +1620,7 @@ static void out_version(void)
> printf(UTIL_LINUX_VERSION);
> }
>
> +#define DEFAULT_OFFSET_FILE "/etc/time_offset"
> /*
> * usage - Output (error and) usage information
> *
> @@ -1577,6 +1651,10 @@ static void usage(const char *fmt, ...)
> " --adjust adjust the RTC to account for systematic drift since\n"
> " the clock was last set or adjusted\n"), usageto);
> fputs(_(" -c, --compare periodically compare the system clock with the CMOS clock\n"), usageto);
> + fprintf(usageto,
> + _(" --offset [file] instead of setting the clock, write an offset to file.\n"
> + " when reading the time, add this offset to the hardware time.\n"
> + " (default: %s)\n"), DEFAULT_OFFSET_FILE);
> #ifdef __linux__
> fputs(_(" --getepoch print out the kernel's hardware clock epoch value\n"
> " --setepoch set the kernel's hardware clock epoch value to the \n"
> @@ -1653,6 +1731,7 @@ int main(int argc, char **argv)
> /* Long only options. */
> enum {
> OPT_ADJFILE = CHAR_MAX + 1,
> + OPT_OFFSET,
> OPT_BADYEAR,
> OPT_DATE,
> OPT_DIRECTISA,
> @@ -1698,6 +1777,7 @@ int main(int argc, char **argv)
> {"test", 0, 0, OPT_TEST},
> {"date", 1, 0, OPT_DATE},
> {"epoch", 1, 0, OPT_EPOCH},
> + {"offset", 2, 0, OPT_OFFSET},
> #ifdef __linux__
> {"rtc", 1, 0, 'f'},
> #endif
> @@ -1837,6 +1917,10 @@ int main(int argc, char **argv)
> case OPT_PREDICT_HC:
> predict = TRUE; /* --predict-hc */
> break;
> + case OPT_OFFSET:
> + offset_file_name = /* --offset */
> + optarg ? optarg : DEFAULT_OFFSET_FILE;
> + break;
> #ifdef __linux__
> case 'f':
> rtc_dev_name = optarg; /* --rtc */
>
--
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