man2: adjtimex.2 : add info about Clock source
Subsystems (3)
PATCH 1/1 man2: adjtimex.2 : add info about Clock source
This is a patch to the adjtimex.2 file that add more detail about clock source in man page which is asked to be fixed. I got this information from standard document RFC5909 which is available at https://tools.ietf.org/html/rfc5905#appendix-A.5.5.1
--- man2/adjtimex.2 | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-)
man2/adjtimex.2 +22 -2
@@ -276,8 +276,28 @@ Mode (0 = Phase Locked Loop, 1 = Frequency Locked Loop; read-only). .\" commit eea83d896e318bda54be2d2770d2c5d6668d11db .\" Author: Roman Zippel <[email protected]> Clock source (0 = A, 1 = B; read-only). -.\" FIXME It would be helpful to have some explanation of what -.\" "Clock source" is. +Clock source is used to synchronized the time.It can be any standard clock +sources like : + +Geosynchronous Orbit Environment Satellite +Global Position System +Galileo Positioning System +Generic pulse-per-second +Inter-Range Instrumentation Group +LF Radio WWVB Ft. Collins, CO 60 kHz +LF Radio DCF77 Mainflingen, DE 77.5 kHz +LF Radio HBG Prangins, HB 75 kHz +LF Radio MSF Anthorn, UK 60 kHz +LF Radio JJY Fukushima, JP 40 kHz, Saga, JP 60 kHz +MF Radio LORAN C station, 100 kHz +MF Radio Allouis, FR 162 kHz +HF Radio CHU Ottawa, Ontario +HF Radio WWV Ft. Collins, CO +HF Radio WWVH Kauai, HI +NIST telephone modem +NIST telephone modem +USNO telephone modem +European telephone modem .PP Attempts to set read-only .I status
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Hello!
I'm not sure that this is what is meant by "Clock source" in struct timex.h. STA_CLK can take only two values ("A" and "B"), and is read-only. It was added in commit ee9851b218b8bafa22942b5404505ff3d2d34324 (kernel 2.6.25) at the same time MOD_CLKA and MOD_CLKB were removed.
Quoted 16 lines
tree
581f455e02ed3d03e543642b5d54b83dc75d47c7
parentee9851b218b8bafa22942b5404505ff3d2d34324
author Roman Zippel <[email protected]> Thu May 1 04:34:33 2008 -0700 committer Linus Torvalds <torvalds-de/[email protected]> Thu May 1 08:03:58 2008 -0700ntp: NTP4 user space bits update
This adds a few more things from the ntp nanokernel related to user space. It's now possible to select the resolution used of some values via
STA_NANOand the kernel reports in which mode it works (pll/fll).If some values for
adjtimex()are outside the acceptable range, they are now simply normalized instead of letting the syscall fail. I removed MOD_CLKA/MOD_CLKB as the mapping didn't really makes any sense, the kernel doesn't support setting the clock.
Quoted 5 lines
Signed-off-by Roman Zippel <[email protected]>Cc john stultz <johnstul-r/[email protected]>Cc Thomas Gleixner <[email protected]>Signed-off-by Andrew Morton <akpm-de/[email protected]>Signed-off-by Linus Torvalds <torvalds-de/[email protected]>
Originally, A and B were present to distinguish two modes of functioning:
whether an external clock is present or not. If an external clock system adjusts the local clock, then NTP is not used. In the case of Linux, I think this distinction between sources "A" and "B" is present for historical reasons, and because it was present in the reference implementation for ntp but I don't see where it's used in the kernel. See this for example of use of STA_CLK in another implementation:
http://www.slac.stanford.edu/comp/unix/package/rtems/src/ssrlApps/ntpNanoclock/api.htm
And this for the NTP standard, version 4:
http://www.eecis.udel.edu/~mills/ntp/html/extern.html
In Linux, there are two ways to adjust the clock. If it's not by NTP, then it can be through the use of system call clock_adjtime(2) (for which there is no man page yet, see clock_settime(2) to get an idea of the interface) which uses a function pointer clock_adj declared in a k_clock struct, which can be initialised to function posix_clock_realtime_adj. (Everything is in kernel/time/posix-timers.c.) Eventually, this boils down to using do_adjtimex, just as adjtimex(2) does. I guess STA_CLK should be set/reset with one of the method and not the other, if my understanding is correct, but it's not. Maybe because it's unused anyway?
Laurent
Quoted 34 lines · Punit Vara
This is a patch to the adjtimex.2 file that add more detail about clock source in man page which is asked to be fixed. I got this information from standard document RFC5909 which is available at https://tools.ietf.org/html/rfc5905#appendix-A.5.5.1
Signed-off-by Punit Vara <[email protected]>--- man2/adjtimex.2 | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-)man2/adjtimex.2 +15
-2@@ -276,8 +276,28 @@ Mode (0 = Phase Locked Loop, 1 = Frequency Locked Loop; read-only). .\" commit eea83d896e318bda54be2d2770d2c5d6668d11db .\" Author: Roman Zippel <[email protected]> Clock source (0 = A, 1 = B; read-only). -.\" FIXME It would be helpful to have some explanation of what -.\" "Clock source" is. +Clock source is used to synchronized the time.It can be any standard clock +sources like : + +Geosynchronous Orbit Environment Satellite +Global Position System +Galileo Positioning System +Generic pulse-per-second +Inter-Range Instrumentation Group +LF Radio WWVB Ft. Collins, CO 60 kHz +LF Radio DCF77 Mainflingen, DE 77.5 kHz +LF Radio HBG Prangins, HB 75 kHz +LF Radio MSF Anthorn, UK 60 kHz +LF Radio JJY Fukushima, JP 40 kHz, Saga, JP 60 kHz +MF Radio LORAN C station, 100 kHz +MF Radio Allouis, FR 162 kHz
man2/adjtimex.2 Mode (0 = Phase Locked Loop, 1 = Frequency Locked Loop; read-only). · line 303
Quoted 10 lines
man2/adjtimex.2 +7
-0+HF Radio CHU Ottawa, Ontario +HF Radio WWV Ft. Collins, CO +HF Radio WWVH Kauai, HI +NIST telephone modem +NIST telephone modem +USNO telephone modem +European telephone modem .PP Attempts to set read-only .I status
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