MFC r326276:

various: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Revert r253748,253749

This WIP should not have been committed yet.

Pointyhat to: avg

remove needless inclusion of machine/cpu.h in userland

MFC after: 21 days

Rework all non-contributed files that use `struct timezone'.

This structure is not part of POSIX. According to POSIX, gettimeofday()
has the following prototype:

int gettimeofday(struct timeval *restrict tp, void *restrict tzp);

Also, POSIX states that gettimeofday() shall return 0 (as long as tzp is
not used). Remove dead error handling code. Also use NULL for a
nul-pointer instead of integer 0.

While there, change all pieces of code that only use tv_sec to use
time(3), as this provides less overhead.

If not compiled for debugging, redirect standard input/output/error
to /dev/null before becoming a daemon.

Correct various mistakes in the last commit.

Use sysctlbyname

Invoke tzset(3) within the main loop to catch changes to /etc/localtime
when running as a daemon in the hope that it will fix situations
where the CMOS clock was apparently set using the stale TZ offset.

Use __FBSDID() to quiet GCC 3.3 warnings.

o Use real prototypes
o Remove __P.
o main(int, char *[])

Fix a prototype and set WARNS=2.

Submitted by: Mike Barcroft <mike@q9media.com>

$Id$ -> $FreeBSD$

Correct use of .Nm. Add missing .El. Add rcsid. Remove unused #include.

Implement Helbig idea of offset calculation reducing mktime() calls
Immediately exit if /etc/wall_cmos_clock not present

Add workaround suggestion for 'nonexistent time' diagnostic

Minimize clock drift between getting and setting time
Submitted by: bde

Add Id, add usage function.

compare return value from getopt against -1 rather than EOF, per the final
posix standard on the topic.

Detect if /etc/wall_cmos_clock gone while adjkerntz paused.

Dynamically sense /etc/wall_cmos_clock presence/absense

Fix error with multiply 'adjkerntz -a' copies running.
Manage adjkerntz kernel variable even for UTC clocks.
Code cleanup.

Remove trailing whitespace.

Use more AI to predict initial/final isdst,
latest isdst preffered.

Use timelocal() instead of mktime() hack

Fix resetting adjkerntz to 0 (pointed by Bruce),
forget to initialize mib variable.

Optimize setting of DISRTCSET

Clean internal logic, helps for some unusual cases

-i case goes to background pause and acts like -a case on receiving
SIGTERM. This helps to keep CMOS clock updated before reboot.
Idea from J.Wunsch.

Restore back -i, -a

Remove options, run adjkerntz as daemon now

Now:
adjkerntz -i writes kernel clock only, don't touch RTC clock
adjkerntz -a writes RTC clock only, don't touch kernel clock

Modify adjkerntz to not write RTC clock per initial call,
suggested by Bruce

rewritted to use sysctl, no more /var/run/.adjkerntz now

Cosmetique patch from bde

Fix sign of offset diff.
Use Bruce initial/final hour scheme to avoid critical hours.

This commit was generated by cvs2svn to compensate for changes in r867,
which included commits to RCS files with non-trunk default branches.

Attempt to import adjkerntz...