[Linuxptp-users] Question about meanPathDelay (possible bug?)

[Wolfgang W. <wol...@gm...>]

Hello,

I have a question about the calculation of the meanPathDelay by the  
functions process_delay_resp() and clock_path_delay().
The standard says the following about the meanPathDelay computation  
(section 11.3.2):
<meanPathDelay> shall be computed as: <meanPathDelay> = [(t2 - t3) +  
(receiveTimestamp of Delay_Resp message – originTimestamp of Sync message)  
– correctionField of Sync message – correctionField of Delay_Resp  
message]/2.

I'm not sure, but I think the "receiveTimestamp of Delay_Resp  
message"-part is not implemented correctly in LinuxPTP.

The function process_delay_resp() calls clock_path_delay() as follows:

	clock_path_delay(p->clock, p->delay_req->hwts.ts, m->ts.pdu,  
m->header.correction);

The third argument is used by clock_path_delay() as what is called t4 in  
the standard.
As far as I understand the code, the third argument (m->ts.pdu) is the  
ingress timestamp on the slave of the DelayResp-message.
But I think what should be passed here should be the ingress timestamp on  
the master of the DelayReq-message, which is contained in the  
"receiveTimestamp"-field of the DelayResp-message (rsp->receiveTimestamp).

Any comments on what is actually correct are welcome :)
I'm new to LinuxPTP and try to use it to improve my understanding of 1588.

regards,
Wolfgang Wallner