netdev - Re: [RFC 1/3] ptp: Implement timex esterror support

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Message-ID: <fa372172-ef1c-4cbb-8126-7665d3e15251@machnikowski.net>
Date: Thu, 15 Aug 2024 11:47:45 +0200
From: Maciek Machnikowski <maciek@...hnikowski.net>
To: Richard Cochran <richardcochran@...il.com>
Cc: netdev@...r.kernel.org, jacob.e.keller@...el.com, vadfed@...a.com,
 darinzon@...zon.com, kuba@...nel.org
Subject: Re: [RFC 1/3] ptp: Implement timex esterror support



On 15/08/2024 06:23, Richard Cochran wrote:
> On Tue, Aug 13, 2024 at 12:56:00PM +0000, Maciek Machnikowski wrote:
>> The Timex structure returned by the clock_adjtime() POSIX API allows
>> the clock to return the estimated error. Implement getesterror
>> and setesterror functions in the ptp_clock_info to enable drivers
>> to interact with the hardware to get the error information.
> 
> So this can be implemented in the PTP class layer directly.  No need
> for driver callbacks.
Sorry - missed that one in the previous answer.

I can implement a generic support in case all the information are
exchanged locally, but the driver hooks are needed for a use case of
separate function owning the synchronization, or an autonomous sync
devices (Time Cards). Would a fallback if getesterror==NULL be enough?

Regards,
Maciek

>  
>> getesterror additionally implements returning hw_ts and sys_ts
>> to enable upper layers to estimate the maximum error of the clock
>> based on the last time of correction.
> 
> But where are the upper layers?
> 
>> This functionality is not
>> directly implemented in the clock_adjtime and will require
>> a separate interface in the future.
> 
> We don't add interfaces that have no users.
> 
> Thanks,
> Richard