From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932597Ab3D2VW0 (ORCPT ); Mon, 29 Apr 2013 17:22:26 -0400 Received: from moutng.kundenserver.de ([212.227.126.186]:62405 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932466Ab3D2VWZ (ORCPT ); Mon, 29 Apr 2013 17:22:25 -0400 From: Arnd Bergmann To: Linus Torvalds Subject: Re: [GIT PATCH] char/misc patches for 3.10-rc1 Date: Mon, 29 Apr 2013 23:22:18 +0200 User-Agent: KMail/1.12.2 (Linux/3.8.0-18-generic; KDE/4.3.2; x86_64; ; ) Cc: Greg KH , David Brown , Andrew Morton , Linux Kernel Mailing List , Nicolas Pitre References: <20130429162115.GA6893@kroah.com> <201304292250.47699.arnd@arndb.de> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201304292322.18971.arnd@arndb.de> X-Provags-ID: V02:K0:a+3fgi/rgfrQ513Dly0alMM/k4FbGkCoWBKjEfuFhNQ 6XoXK9BEfflmusK/waOAgA0q7boatHEK9Izn+ZYS0tWK6yh5HK a4OQvADdMUQbUhnqtUr3BvLf4Cb32ZfyREc/SsuaYL2Kbw3ZcT GXT05AjFrt+i4xDjENkJgwNtr26nPP4BbaexttzrWrMV1em+Q2 p3t8JyuPOa46D+KyrZoaxDzTGyX0maAYzem69Sww4eJeg6bXNW H6KcToAxoeVkFh8eZ21nT6B4WiSzMj9eHM90LDsoAkF/jgXXWy CYL+xzgHCPPMyo+j9XmWh0RmJVmReccF11TzIN5rwHFFHz1YPg v8T9cUU3qzorFTGQ45M4= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 29 April 2013, Linus Torvalds wrote: > On Mon, Apr 29, 2013 at 1:50 PM, Arnd Bergmann wrote: > > > > Fair enough. Of course the distinction here is not based on what it > > does, but how it gets used. > > Even technically, a "bus" generally has a topology. It has addresses, > and it has a protocol. > > i2c is a bus. PCI is a bus. And something like SSB is a bus. There is > a protocol, there's device with identity on the bus, there's stuff > going on. Right. I was looking at it from the linux driver model perspective, where we already call a lot of things a bus that are not at all one in the engineering sense. > The SBBI driver has neither addresses nor a protocol. It's literally > just an embedded on-chip serial device as far as I can tell. There's > nothing "bus" about it. It's just a hose. > > Yeah, yeah, at some point you can call "anything" a bus. I could call > my little two-seater car a "school bus", because it has wheels, it's > even yellow exactly like the school buses around here. And I can put a > child in it. So my little yellow two-seater must be a bus too. It's > all just how you define your words. > > But it's a damn big reach. I didn't use to call the serial line > connecting my computer to the modem a "bus". Even if it connected two > devices. It seems I looked too briefly. As you point out and David already confirmed, there is only one device on the other side, which is indeed a major difference to e.g. SPI, which seems rather similar otherwise but can use chip-select pins to multiplex between different endpoints. Certainly this hardware could do the same, but you are right that it's not relevant because it doesn't do that in practice. Arnd