linux-kernel - Re: [PATCH net-next RFC 1/1] ptp: use extts interface for the measured external offset

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Message-ID: <490abfce-47b6-430c-8fc1-99536284c1a6@intel.com>
Date:   Mon, 13 Nov 2023 15:00:15 -0800
From:   Jacob Keller <jacob.e.keller@...el.com>
To:     Min Li <lnimi@...mail.com>, <richardcochran@...il.com>
CC:     <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        Min Li <min.li.xe@...esas.com>
Subject: Re: [PATCH net-next RFC 1/1] ptp: use extts interface for the
 measured external offset

On 11/13/2023 1:50 PM, Min Li wrote:
> From: Min Li <min.li.xe@...esas.com>
> 
> This change is for the PHC devices that can measure the
> phase offset between PHC signal and the external signal, such
> as GNSS. With this change, ts2phc can use the existing extts
> interface to retrieve measurement offset so that the alignment
> between PHC and the external signal can be achieved.
> 
> Signed-off-by: Min Li <min.li.xe@...esas.com>
> ---

Ok, so this adds a new event type "extoff" which is for eternal
timestamp offset, and it allows reporting the offset instead of the raw
time.

Userspace can request this feature via the new PTP_EXT_OFFSET flag, and
drivers will report it as a new event type.

You mention GNSS, but is there an example or a link to a driver change
you could provide to show its use?

I think the concept seems reasonable and the code seems correct.

Thanks,
Jake