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From:   Linus Walleij <linus.walleij@linaro.org>
Date:   Sat, 23 Apr 2022 17:09:49 +0200
Message-ID: <CACRpkda8pT-mzZXDAoGLnK2xZ9TtrvMqY49oHY6E1C4LSsQhcA@mail.gmail.com>
Subject: Re: [PATCH] dt-bindings: gnss: Add Broacom BCM4751 family bindings
To:     Dmitry Osipenko <dmitry.osipenko@collabora.com>
Cc:     Johan Hovold <johan@kernel.org>, Rob Herring <robh+dt@kernel.org>,
        David Heidelberg <david.heidelberg@collabora.com>,
        Svyatoslav Ryhel <clamor95@gmail.com>,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
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On Sat, Apr 23, 2022 at 4:12 PM Dmitry Osipenko
<dmitry.osipenko@collabora.com> wrote:
> On 4/23/22 00:50, Linus Walleij wrote:
> > On Mon, Apr 18, 2022 at 1:19 PM Dmitry Osipenko
> > <dmitry.osipenko@collabora.com> wrote:
> >
> >> What are the chances of seeing the kernel driver for BCM4751+?
> >
> > The kernel does not normally drive the GPS. The kernel has a small driver
> > dealing with hardware power on/off of the GPS and exposing
> > /dev/gnss0 to userspace.
> >
> > See Johans lecture at:
> > https://events19.linuxfoundation.org/wp-content/uploads/2017/12/The-GNSS-Subsystem-Johan-Hovold-Hovold-Consulting-AB.pdf
>
> IIUC, driver also should be needed for the firmware uploading, similarly
> to the BCM WiFi/BT chips, isn't it?

As far as I can tell from the filesystem on this phone there is no firmware
so it is flashed into the GPS chip.

> > gpsd is the most common userspace daemon for GPS.
> > gpsd will then talk to /dev/gnss0 as any other TTY IIUC.
> >
> > Replicant has a free implementation of the "MEIF" API for this GPS,
> > I think what is needed is really for someone to pick up, polish and
> > contribute that to gpsd
> > https://git.replicant.us/contrib/PaulK/bcm4751/
>
> My main curiosity is about whether you already have a working driver
> prototype, something you could share with us all, so we could start
> playing with it too :)

It's on my TODO whenever there is time, but I have small kids so not
so much time... I was hoping for the jolly people in postmarketOS to
chime in because they seem to have a bunch of people with lots of
time on their hands available :D

Yours,
Linus Walleij