linux-kernel - Re: [Letux-kernel] [PATCH v5 3/5] misc serdev: Add w2sg0004 (gps receiver) power control driver

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Message-ID: <20180212152618.GC13962@amd>
Date:   Mon, 12 Feb 2018 16:26:18 +0100
From:   Pavel Machek <pavel@....cz>
To:     Johan Hovold <johan@...nel.org>
Cc:     "H. Nikolaus Schaller" <hns@...delico.com>,
        Mark Rutland <mark.rutland@....com>,
        DTML <devicetree@...r.kernel.org>,
        Thierry Reding <treding@...dia.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Tony Lindgren <tony@...mide.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Russell King <linux@...linux.org.uk>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Kevin Hilman <khilman@...libre.com>,
        Benoît Cousson <bcousson@...libre.com>,
        kernel@...a-handheld.com,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        Andreas Färber <afaerber@...e.de>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Letux-kernel] [PATCH v5 3/5] misc serdev: Add w2sg0004 (gps
 receiver) power control driver

Hi!

> > Let's restart this discussion and focus on the main roadblock (others
> > are minor details which can be sorted out later).
> > 
> > If it feels like a hack, the key issue seems to me to be the choice of
> > the API to present the GPS data to user space. Right?
> 
> Or even more fundamentally, does this belong in the kernel at all?

Yes, it does.

> Given that we'd still depend on gpsd and other, proprietary, daemons to
> actually parse and use (also for control) the plethora of GPS protocols
> available, it may even be best to just keep it all in user space.

No. We'd want to move away from gpsd in the long
term. (/dev/input/mice was in similar situation.)

> Now, if we'd ever have a proper GPS framework that handled everything in
> kernel space (i.e. no more gpsd) then we would be able to write kernel
> drivers that also take care of PM. But perhaps that's unlikely to ever
> be realised given the state of things (proprietary protocols, numerous
> quirky implementations, etc).

That is what needs to happen.

> The kernel is probably not the place to be working around issues like
> that, even if serdev at least allows for such hacks to be fairly
> isolated in drivers (unlike some of the earlier proposals touching core
> code).

Oh, kernel is indeed right place to provide hardware abstraction --
and that includes bug workarounds.

We'd like unmodified userspace to run on any supported hardware,
remember?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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