git: 6834c2660904 - stable/15 - adjtime(2): document that delta can be NULL

The branch stable/15 has been updated by kevans:

URL: https://cgit.FreeBSD.org/src/commit/?id=6834c2660904ef6d1fdade32e2dddda55778b989

commit 6834c2660904ef6d1fdade32e2dddda55778b989
Author:     Kyle Evans <[email protected]>
AuthorDate: 2026-06-20 13:55:26 +0000
Commit:     Kyle Evans <[email protected]>
CommitDate: 2026-08-06 23:35:25 +0000

    adjtime(2): document that delta can be NULL
    
    The current verbiage somewhat indicates that always adjusts the time,
    which hasn't been true as far back as I had the energy to `git blame`.
    
    Reviewed by:    imp
    
    (cherry picked from commit 8ed580b1d3811e73e25db3d8a9fd235156c65387)
---
 lib/libsys/adjtime.2 | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/lib/libsys/adjtime.2 b/lib/libsys/adjtime.2
index ee8befe09ca9..ad2467d5ef61 100644
--- a/lib/libsys/adjtime.2
+++ b/lib/libsys/adjtime.2
@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd May 13, 2021
+.Dd June 19, 2026
 .Dt ADJTIME 2
 .Os
 .Sh NAME
@@ -46,6 +46,7 @@ makes small adjustments to the system time, as returned by
 advancing or retarding it
 by the time specified by the timeval
 .Fa delta .
+.Pp
 If
 .Fa delta
 is negative, the clock is
@@ -55,6 +56,13 @@ If
 .Fa delta
 is positive, a larger increment than normal
 is used.
+.Fa delta
+may also be a
+.Dv NULL
+pointer to fetch
+.Fa olddelta
+without making any adjustment.
+.Pp
 The skew used to perform the correction is generally a fraction of one percent.
 Thus, the time is always
 a monotonically increasing function.
@@ -65,7 +73,9 @@ may not be finished when
 is called again.
 If
 .Fa olddelta
-is not a null pointer,
+is not a
+.Dv NULL
+pointer,
 the structure pointed to will contain, upon return, the
 number of microseconds still to be corrected
 from the earlier call.