linux-kernel - Re: [PATCH v4 0/4] Bluetooth/gnss: GNSS support for TiWi chips

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Message-ID: <xlnssb5ifmxcgklaraxhoreu6ub4oq6jjxev6cx2b6dtcn3lax@3wsm7szrjki2>
Date: Thu, 16 Jan 2025 02:10:06 +0100
From: Sebastian Reichel <sre@...nel.org>
To: Johan Hovold <johan@...nel.org>
Cc: Andreas Kemnade <andreas@...nade.info>, marcel@...tmann.org, 
	luiz.dentz@...il.com, pmenzel@...gen.mpg.de, jirislaby@...nel.org, 
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org, 
	Adam Ford <aford173@...il.com>, Tony Lindgren <tony@...mide.com>, 
	tomi.valkeinen@...asonboard.com, Péter Ujfalusi <peter.ujfalusi@...il.com>, 
	robh@...nel.org, hns@...delico.com
Subject: Re: [PATCH v4 0/4] Bluetooth/gnss: GNSS support for TiWi chips

Hi,

On Tue, Jan 14, 2025 at 12:57:05PM +0100, Johan Hovold wrote:
> [ +CC: Sebastian ]
> 
> Hi Andreas,
> 
> and sorry about the late reply on this.
> 
> On Thu, Jun 06, 2024 at 08:30:28PM +0200, Andreas Kemnade wrote:
> > Some of these chips have GNSS support. In some vendor kernels
> > a driver on top of misc/ti-st can be found providing a /dev/tigps
> > device which speaks the secretive Air Independent Interface (AI2) protocol.
> 
> Please expand the cover letter and commit messages with more details on
> the protocols and backstory here. I spent hours over the Christmas break
> digging through drivers, git logs and mail archives for information that
> should have been part of the series.
> 
> Specifically, give a better description of these chips which are WiFi
> controllers with Bluetooth primarily and then some have (optional?) FM
> radio and GPS support as well. Some even seem to support NFC too (also
> over HCI?).

Your TI WiLink chip description matches my understanding. In
addition to some chips not support the optional features, there
may also be some boards with cripped support (i.e. when an antenna
is not connected). So having a DT property flag to describe working
GPS would be an option.

> Provide some background on the ti-st driver, which have now been
> removed; the fact that we already had two drivers for these chips with
> one only supporting the Bluetooth (and later some PM) bits; say
> something about the FM driver which someone also recently decided to
> remove on questionable grounds.
> 
> Please also refer to the prior attempts at adding support for the
> various subfunctions to the driver (e.g. Sebastian's discussion with
> Marcel on how to possibly abstract this in Bluetooth core), such as:
> 
> 	https://lore.kernel.org/lkml/0C9AD246-B511-4E59-888F-47EAB034D4BF@holtmann.org/

I haven't really worked with TI WiLink in the last 5 years. The
Droid 4, which I played around with, is no usable for me since
the 3G network has been killed (and the Droid 4 only supports the
US band for 4G). As visible from the series you linked, my last
plans were to kill ti-st, which pre-dates serdev. The hcill
bluetooth driver was introduced by Rob Herring together with
the initial serdev core as a cleaner replacement.

Greetings,

-- Sebastian

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