[LinuxPPS] select() on /dev/pps

[Xavier Bestel]

I forgot the kernel version I'm using:
Linux lmde 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt7-1 (2015-03-01) 
x86_64 GNU/Linux

     Xav

Le 30/07/2015 09:39, Xavier Bestel a écrit :
> Hi,
>
> for an application of mine I would need to be able to wait for events 
> on a char device and on a PPS device; on the char device the select() 
> call is the obvious candidate, but it doesn't seem to work on the PPS 
> device. That is, select() always returns immediately telling some data 
> is available, and a PPS_FETCH either returns immediately if flags=0 or 
> waits for 1s if flags=PPS_TIME_INVALID;
>
> That looks wrong to me. IMHO select() should wait for 1s and PPS_FETCH 
> should "consume" the data without waiting.
> If it should work, could you tell me where is my code wrong ?
>
> Thanks,
>
>     Xav
>
>
> #include <sys/select.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <linux/pps.h>
>
> int main(int argc, char *argv[])
> {
>     if(argc != 2) {
>         fprintf(stderr, "usage: %s device\n", argv[0]);
>         exit(1);
>     }
>     int fd = open(argv[1], O_RDWR);
>     if(fd < 0) {
>         fprintf(stderr, "error opening %s: %m\n", argv[1]);
>         exit(1);
>     }
>     fd_set set;
>     while(1) {
>         struct timeval tv;
>         tv.tv_sec = 2;
>         tv.tv_usec = 0;
>         FD_ZERO(&set);
>         FD_SET(fd, &set);
>         int sel = select(fd + 1, &set, NULL, NULL, &tv);
>         printf("select returns %d\n", sel);
>         if(FD_ISSET(fd, &set)) {
>             struct pps_fdata fdata;
>             fdata.timeout.sec = 0;
>             fdata.timeout.nsec = 0;
>             fdata.timeout.flags = PPS_TIME_INVALID; // or 0
>             if(ioctl(fd, PPS_FETCH, &fdata) < 0) {
>                 fprintf(stderr, "no PPS : %m");
>                 exit(1);
>             }
>             printf("fetch returns\n");
>         }
>         }
>     return 0;
> }
>
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