Le 17/09/2018 à 17:12, Richard Cochran a écrit :
> On Mon, Sep 17, 2018 at 08:14:04AM +0000, FUSTE Emmanuel wrote:
>> Running the command compiled without PTP_SYS_OFFSET_PRECISE support on a
>> kernel (and perhaps the hardware) with PTP_SYS_OFFSET_PRECISE will
>> return a definitively wrong answer.
> Yeah, this isn't ideal.
>
> Saying "unknown" is also a bit weird. People will wonder, why can't
> you tell?
>
> How about this:
>
> /* from linux kernel v4.19-rc4 */
> struct compat_caps {
> int max_adj; /* Maximum frequency adjustment in parts per billon. */
> int n_alarm; /* Number of programmable alarms. */
> int n_ext_ts; /* Number of external time stamp channels. */
> int n_per_out; /* Number of programmable periodic signals. */
> int pps; /* Whether the clock supports a PPS callback. */
> int n_pins; /* Number of input/output pins. */
> /* Whether the clock supports precise system-device cross timestamps */
> int cross_timestamping;
> int rsv[13]; /* Reserved for future use. */
> };
>
> and then
>
> static int do_caps(clockid_t clkid, int cmdc, char *cmdv[])
> {
> union {
> struct ptp_clock_caps caps;
> struct compat_caps compat;
> } u;
> ...
> // check u.compat.cross_timestamping
> }
>
Yes, clever and more future proof. Damm, it was a long time since I did
real C... |-)
diff --git a/phc.h b/phc.h
index 154e35e..2fe33c4 100644
--- a/phc.h
+++ b/phc.h
@@ -21,6 +21,19 @@
#include "missing.h"
+/* from linux kernel v4.15 */
+struct compat_caps {
+ int max_adj; /* Maximum frequency adjustment in parts per billon. */
+ int n_alarm; /* Number of programmable alarms. */
+ int n_ext_ts; /* Number of external time stamp channels. */
+ int n_per_out; /* Number of programmable periodic signals. */
+ int pps; /* Whether the clock supports a PPS callback. */
+ int n_pins; /* Number of input/output pins. */
+ /* Whether the clock supports precise system-device cross timestamps */
+ int cross_timestamping;
+ int rsv[13]; /* Reserved for future use. */
+};
+
/**
* Opens a PTP hardware clock device.
*
diff --git a/phc_ctl.c b/phc_ctl.c
index 4a78a19..d33ff1f 100644
--- a/phc_ctl.c
+++ b/phc_ctl.c
@@ -334,14 +334,17 @@ static int do_freq(clockid_t clkid, int cmdc, char
*cmdv[])
static int do_caps(clockid_t clkid, int cmdc, char *cmdv[])
{
- struct ptp_clock_caps caps;
+ union {
+ struct ptp_clock_caps caps;
+ struct compat_caps compat;
+ } u;
if (clkid == CLOCK_REALTIME) {
pr_warning("CLOCK_REALTIME is not a PHC device.");
return 0;
}
- if (ioctl(CLOCKID_TO_FD(clkid), PTP_CLOCK_GETCAPS, &caps)) {
+ if (ioctl(CLOCKID_TO_FD(clkid), PTP_CLOCK_GETCAPS, &u)) {
pr_err("get capabilities failed: %s",
strerror(errno));
return -1;
@@ -353,12 +356,14 @@ static int do_caps(clockid_t clkid, int cmdc, char
*cmdv[])
" %d programable alarms\n"
" %d external time stamp channels\n"
" %d programmable periodic signals\n"
- " %s pulse per second support",
- caps.max_adj,
- caps.n_alarm,
- caps.n_ext_ts,
- caps.n_per_out,
- caps.pps ? "has" : "doesn't have");
+ " %s pulse per second support\n"
+ " %s precise system-device cross timestamps support",
+ u.caps.max_adj,
+ u.caps.n_alarm,
+ u.caps.n_ext_ts,
+ u.caps.n_per_out,
+ u.caps.pps ? "has" : "doesn't have",
+ u.compat.cross_timestamping ? "has" : "doesn't have");
return 0;
}
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