From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753775Ab3AXLkE (ORCPT ); Thu, 24 Jan 2013 06:40:04 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:44335 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752956Ab3AXLkA (ORCPT ); Thu, 24 Jan 2013 06:40:00 -0500 Date: Thu, 24 Jan 2013 12:39:48 +0100 From: Wolfram Sang To: Mark Brown Cc: Stephen Warren , Naveen Krishna Chatradhi , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org, grundler@chromium.org, devicetree-discuss@lists.ozlabs.org, ben-linux@fluff.org, khali@linux-fr.org, naveen@chromium.org Subject: Re: [PATCH 1/2] i2c-core: Add gpio based bus arbitration implementation Message-ID: <20130124113948.GD12933@pengutronix.de> References: <1355464254-12768-1-git-send-email-ch.naveen@samsung.com> <1355464254-12768-2-git-send-email-ch.naveen@samsung.com> <50CB4E99.9060506@wwwdotorg.org> <20121215142135.GB22033@opensource.wolfsonmicro.com> <20130124111329.GC12933@pengutronix.de> <20130124111845.GO4955@opensource.wolfsonmicro.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="a2FkP9tdjPU2nyhF" Content-Disposition: inline In-Reply-To: <20130124111845.GO4955@opensource.wolfsonmicro.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: 2001:6f8:1178:2:21e:67ff:fe11:9c5c X-SA-Exim-Mail-From: wsa@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --a2FkP9tdjPU2nyhF Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jan 24, 2013 at 07:18:47PM +0800, Mark Brown wrote: > On Thu, Jan 24, 2013 at 12:13:29PM +0100, Wolfram Sang wrote: > > On Sat, Dec 15, 2012 at 11:21:36PM +0900, Mark Brown wrote: >=20 > > > also get things like read operations which appear as multiple > > > transactions on the I2C bus so require something higher level than wh= at > > > multi-master provides. >=20 > > I don't get what you mean here. Can you elaborate? >=20 > A read is typically implemented as a write of the register address > followed by a read of the value, usually with the ability to free the > bus in between. If two devices attempt to access the register map > simultaneously this results in the address going wrong. Could happen. But in what situations will one not use repeated start here? Especially when designing a multi-master bus? --=20 Pengutronix e.K. | Wolfram Sang | Industrial Linux Solutions | http://www.pengutronix.de/ | --a2FkP9tdjPU2nyhF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlEBHYQACgkQD27XaX1/VRsAdQCdHPM40PqJBYznKnHAljriBDlU XOsAnAkqEGcQ6Y34Ge9EqF0qt6/HfHEQ =pzuW -----END PGP SIGNATURE----- --a2FkP9tdjPU2nyhF--