[CC += linux-man@] On Tue, 25 Aug 2020 at 16:13, Tony May <tony.may@xxxxxxxxxxxxx> wrote: > > Dear Michael Kerrisk, > > I have been using PTP and found the documentation > patch provided by Richard Cochran: > https://lore.kernel.org/patchwork/patch/868609/. This patch > included a bug which now appears in > https://man7.org/linux/man-pages/man2/clock_gettime.2.html > > I think the example code he provides contains a bug: > > struct timeval tv; > clockid_t clkid; > int fd; > > fd = open("/dev/ptp0", O_RDWR); > clkid = FD_TO_CLOCKID(fd); > clock_gettime(clkid, &tv); > > The clock_gettime function requires a timespec not a > timeval variable, so the code should be: > > struct timespec ts; > clockid_t clkid; > int fd; > > fd = open("/dev/ptp0", O_RDWR); > clkid = FD_TO_CLOCKID(fd); > clock_gettime(clkid, &ts); > > I have a running test application based on my changes, > so I am confident the modified code works. Thanks, Tony. I applied the patch below. Cheers, Michael diff --git a/man2/clock_getres.2 b/man2/clock_getres.2 index c0e486c2a..8fc7c6fef 100644 --- a/man2/clock_getres.2 +++ b/man2/clock_getres.2 @@ -251,13 +251,13 @@ dynamic clock ID. #define FD_TO_CLOCKID(fd) ((\(ti(clockid_t) (fd) << 3) | CLOCKFD) #define CLOCKID_TO_FD(clk) ((unsigned int) \(ti((clk) >> 3)) -struct timeval tv; +struct timespec ts; clockid_t clkid; int fd; fd = open("/dev/ptp0", O_RDWR); clkid = FD_TO_CLOCKID(fd); -clock_gettime(clkid, &tv); +clock_gettime(clkid, &ts); .EE .in .SH RETURN VALUE -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
