From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 06173323 for ; Wed, 5 Aug 2015 08:40:13 +0000 (UTC) Received: from mail-ob0-f176.google.com (mail-ob0-f176.google.com [209.85.214.176]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 388777D for ; Wed, 5 Aug 2015 08:40:12 +0000 (UTC) Received: by obdeg2 with SMTP id eg2so26529097obd.0 for ; Wed, 05 Aug 2015 01:40:11 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <20150723105726.GC30929@amd> <20150723121441.GB29747@amd> <20150723084251.54da2be0@gandalf.local.home> <20150723154014.GD11162@sirena.org.uk> <55B7FD82.8010806@sonymobile.com> <20150728230743.GO4753@usrtlx11787.corpusers.net> Date: Wed, 5 Aug 2015 10:40:11 +0200 Message-ID: From: Linus Walleij To: Marcel Holtmann Content-Type: text/plain; charset=UTF-8 Cc: Pavel Machek , "ksummit-discuss@lists.linuxfoundation.org" , "riverful.kim@samsung.com" , "kyungmin.park@samsung.com" , John Stultz , Bjorn Andersson , Greg KH Subject: Re: [Ksummit-discuss] [CORE TOPIC] Mainline kernel on a cellphone List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Aug 4, 2015 at 12:36 AM, Marcel Holtmann wrote: > Hi Rob, >> There's been some work by Neil Brown to create a UART slave >> bus[1] (...) > The work on UART slaves (or whatever it will be called eventually) is important > for Bluetooth and most likely GPS and NFC in the future. It then allows to define > all the nasty behind the curtain details of that UART via DT or ACPI in vendor drivers. I agree 100%, and I think I have a simple enough in-kernel usecase so I can get testing these series. It seems GPS and NFC and other code is being kept out of the kernel because of the absense of a UART slave bus and all the hazzle of handling this. > In a perfect world I would prefer we are not using the Bluetooth HCI line discipline > at all. The problem right now is that everybody wants to enable the UART as > /dev/ttyFOO and then move on. However in reality they are not general purpose > TTY devices. The only thing you can ever do with them is tell the Bluetooth > subsystem that there is a TTY device and attach its line discipline to it. This is done from userspace right? I never managed to wrap my head around this because it seemed so odd and plainly hackish. In this ST-Ericsson driver for CG2900: http://marc.info/?l=linux-kernel&m=134873373526049&w=2 the HCI link is used to tunnel things that are not Bluetooth, also GPS and FM radio is controlled over HCI. Yeah sorry, I didn't invent it... the HCI is then run over a UART. Yours, Linus Walleij