On Tue, May 30, 2017 at 11:15:38PM +0200, Thomas Gleixner wrote: > The only user of this facility is ptp_clock, which does not implement any of > those functions. > > Remove them to prevent accidental users. Especially the interval timer > interfaces are now more or less impossible to implement because the > necessary infrastructure has been confined to the core code. Aside of that > it's really complex to make these callbacks implemented according to spec > as the alarm timer implementation demonstrates. If at all then a nanosleep > callback might be a reasonable extension. For now keep just what ptp_clock > needs. > > Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Richard Cochran <[email protected]> For the record, recently someone did try to implement this interface for the i210 card. Although there were issues in the implementation, still I was curious enough to test the performance. https://www.mail-archive.com/[email protected]/msg01738.html The result confirmed my expectation that using the normal system clock sychronized to the PHC using the phc2sys utility yields better performance than the direct timer_settime() implementation. The nanosleep() idea might be worthwhile, but only for devices with directly mapped registers (like in some SoCs) and not for the common PCIe devices. In any case, I am happy to see the timer interface removed, as it is basically useless and gives people false impressions. Could you please include this documentation fix, too? Thanks, Richard ---8<--- diff --git a/Documentation/ptp/ptp.txt b/Documentation/ptp/ptp.txt index ae8fef8..11e904e 100644 --- a/Documentation/ptp/ptp.txt +++ b/Documentation/ptp/ptp.txt @@ -18,7 +18,6 @@ - Adjust clock frequency + Ancillary clock features - - One short or periodic alarms, with signal delivery to user program - Time stamp external events - Period output signals configurable from user space - Synchronization of the Linux system time via the PPS subsystem @@ -48,9 +47,7 @@ User space programs may control the clock using standardized ioctls. A program may query, enable, configure, and disable the ancillary clock features. User space can receive time stamped - events via blocking read() and poll(). One shot and periodic - signals may be configured via the POSIX timer_settime() system - call. + events via blocking read() and poll(). ** Writing clock drivers
