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 AF1E78C7 for ; Mon, 3 Aug 2015 21:35:09 +0000 (UTC) Received: from mail-yk0-f180.google.com (mail-yk0-f180.google.com [209.85.160.180]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 81240147 for ; Mon, 3 Aug 2015 21:35:08 +0000 (UTC) Received: by ykdu72 with SMTP id u72so122095028ykd.2 for ; Mon, 03 Aug 2015 14:35:07 -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> From: Rob Herring Date: Mon, 3 Aug 2015 16:34:48 -0500 Message-ID: To: Linus Walleij Content-Type: text/plain; charset=UTF-8 Cc: Bjorn Andersson , "ksummit-discuss@lists.linuxfoundation.org" , "riverful.kim@samsung.com" , "kyungmin.park@samsung.com" , John Stultz , Pavel Machek , 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 Mon, Aug 3, 2015 at 2:42 AM, Linus Walleij wrote: > On Fri, Jul 31, 2015 at 6:18 PM, Rob Herring wrote: > >> The WiFi side is actually in better shape than BT. With BT, we have >> Bluedroid vs. BlueZ, no real DT bindings to describe BT chips (plenty >> of examples of how not to do it[1]), and chip specific userspace >> initialization (firmware loading, baudrate setup, power mgt). > > I was looking at it at one point and couldn't wrap my head around how > the BT support was devised from a kernel point of view. > > It seems BT chips more often than not sit on a UART connection > (often very high speed) and since there is no "uart bus" or "serial bus" > akin to what we have for I2C or SPI, it is actually impossible to > instantiate them properly in the driver model. Instead BT drivers > are poked and peeked from userspace using the line discipline as > if they were some kind of modem, just in-kernel. Yes, but then there's always some side band signals for regulator control, reset, clocks, wake-up, rf-kill, etc. that needs a glue driver. There's been some work by Neil Brown to create a UART slave bus[1] and I've gotten several other UART device bindings recently, but they all suffer from being one off device bindings done in different ways and I want to see something common here. It also seems the BT folks are working on moving more of the setup into the kernel and creating a proper subsystem. I'm not sure about the details on that. Rob [1] https://lwn.net/Articles/643878/