linux-kernel - Re: [PATCH v2 0/8] gnss: add new GNSS subsystem

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Date:   Thu, 31 May 2018 10:52:42 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andreas Kemnade <andreas@...nade.info>,
        Arnd Bergmann <arnd@...db.de>,
        "H . Nikolaus Schaller" <hns@...delico.com>,
        Pavel Machek <pavel@....cz>,
        Marcel Holtmann <marcel@...tmann.org>,
        Sebastian Reichel <sebastian.reichel@...labora.co.uk>,
        Tony Lindgren <tony@...mide.com>, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 0/8] gnss: add new GNSS subsystem

On Wed, May 30, 2018 at 07:38:22AM -0700, Richard Cochran wrote:
> On Wed, May 30, 2018 at 12:32:34PM +0200, Johan Hovold wrote:
> > Another possible extension is to add generic 1PPS support.
> 
> There are two possibilities to consider.
> 
> 1. If the PPS causes an interrupt, then it should hook into the PPS
>    subsystem.

Registering a PPS child device is what I had in mind for this.

> 2. If the PPS is a HW signal routed for example to the input pin of a
>    MAC based PTP Hardware Clock (PHC), then it would make sense to
>    model the GNSS device as a PHC as well.  This PHC would be readable
>    but not writable, and more importantly it would offer an output
>    signal.  Then user space could use the existing interfaces to
>    dial the PPS signal from one device the another.

Ok.

> (Come to think of it, modeling the GNSS as PHC would also give you the
> interface for #1 as well.)

Thanks
Johan