Return-Path: Date: Thu, 18 Aug 2016 16:13:07 +0100 From: One Thousand Gnomes To: Greg Kroah-Hartman Cc: Marcel Holtmann , "H. Nikolaus Schaller" , Rob Herring , Jiri Slaby , Sebastian Reichel , Pavel Machek , Peter Hurley , NeilBrown , Arnd Bergmann , Linus Walleij , "open list:BLUETOOTH DRIVERS" , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/3] UART slave device bus Message-ID: <20160818161307.5c5d1635@lxorguk.ukuu.org.uk> In-Reply-To: <20160818112435.GA20876@kroah.com> References: <20160818011445.22726-1-robh@kernel.org> <118926C8-F4D0-41F5-B6A8-690E0312F3FB@goldelico.com> <28DDAF2B-2341-403B-80D8-DA0A63F51FF1@holtmann.org> <20160818105521.GB7031@kroah.com> <6A3D5EFF-AC8B-4039-AFF8-652687EB8EDA@holtmann.org> <20160818112435.GA20876@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-ID: > > we have a GPS line discipline? What is that one doing? As far as I > > know all GPS implementations are fully userspace. > > Hm, for some reason I thought that was what n_gsm.c was being used for, > but I could be wrong, I've never seen the hardware that uses that > code... You probably have actually. It's the standard multiplexing protocol on lots of 3G modems. It's an AT command that switches mode. However it illustrates the kind of problems with trying to short circuit the tty_port code. It's entirely possible for a modem to expose the GPS on a channel of the multiplex on the USB connection to the modem which is itself dynamic and can be hot unplugged. Short circuiting the tty_port layer is not a trivial exercise. Alan