linux-kernel - Re: [PATCH 0/7] gnss: add new GNSS subsystem

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Date:   Wed, 25 Apr 2018 08:51:46 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Pavel Machek <pavel@....cz>
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>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 0/7] gnss: add new GNSS subsystem

On Wed, Apr 25, 2018 at 08:26:59AM +0200, Pavel Machek wrote:
> Hi!
> 
> > This series adds a new subsystem for GNSS receivers (e.g. GPS
> > receivers).
> > 
> > While GNSS receivers are typically accessed using a UART interface they
> > often also support other I/O interfaces such as I2C, SPI and USB, while
> > yet other devices use iomem or even some form of remote-processor
> > messaging (rpmsg).
> >     
> > The new GNSS subsystem abstracts the underlying interface and provides a
> > new "gnss" class type, which exposes a character-device interface (e.g.
> > /dev/gnss0) to user space. This allows GNSS receivers to have a
> > representation in the Linux device model, something which is important
> > not least for power management purposes and which also allows for easy
> > detection and (eventually) identification of GNSS devices.
> 
> Actually... no, what you done is not GNSS subsystem. It is generic
> subsystem for a link + some controls, typically for power.
> 
> Yes, that setup is common for GPS receivers, but it is there also for
> modems (droid 4: usb + gpios) and bluetooth dongles (n900: serial +
> gpios).

Those would be handled by other subsystems.

The idea here is that eventually there may be more GNSS specific bits
added, such as 1PPS support that I already mentioned. If someone is
crazy enough to put a location service in the kernel with a more
high-level interface (an in-kernel gpsd) they can try, but I'm more and
more convinced that needs to remain in user space.

I did also already mentioned however, that some hybrid approach may be
doable, such as handling port setup over NMEA/UBX/SiRF from within the
kernel.

Johan