From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750874Ab3AZFAT (ORCPT ); Sat, 26 Jan 2013 00:00:19 -0500 Received: from opensource.wolfsonmicro.com ([80.75.67.52]:40597 "EHLO opensource.wolfsonmicro.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750710Ab3AZFAO (ORCPT ); Sat, 26 Jan 2013 00:00:14 -0500 Date: Sat, 26 Jan 2013 13:00:06 +0800 From: Mark Brown To: Wolfram Sang 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: <20130126050004.GC10580@opensource.wolfsonmicro.com> 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> <20130124113948.GD12933@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="rQ2U398070+RC21q" Content-Disposition: inline In-Reply-To: <20130124113948.GD12933@pengutronix.de> X-Cookie: Make a wish, it might come true. User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --rQ2U398070+RC21q Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Jan 24, 2013 at 12:39:48PM +0100, Wolfram Sang wrote: > On Thu, Jan 24, 2013 at 07:18:47PM +0800, Mark Brown wrote: > > 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? Well, you're depending on the specific drivers doing things that way and it's actually quite rare for the controller drivers in Linux to support I2C_M_NOSTART which discourages this. --rQ2U398070+RC21q Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJRA2LNAAoJELSic+t+oim9Rm8P/RraYYLd7Gsa34rGslUs9cvB NKcRmKMf3Mq0Z/rUVJKnKp6E8M9qyL8qDgx6Xw5QVnxO8qrP8UOAvxJEAG55OYl0 6kAkYqTg0f536N8kWv4X5NtdHp5lFUWSj6+llHtJTUsSQ+UhSxON79UBk1phZi9v DTq8UE2Z1SyoOtCRpwb1403qOX7k4eqM9/yCUuNfbGEM0k/woRSGS475VoFGtU// b5xpxqQ/pF3JJpdXRWkgI62LAcmfiYQU8TiiJWMI0CBdIyzhQfVsQyvkf/nysFOn VzAEFMnc0xbWCQtBjULPgkiNgemAtYWAsAtlT7TqsfTXAKfXp4a/ZRWNGt9UcRYg z8mTP1N0oKGYrgbOdIjKUyrv8ROFG95iYCgOlW2MQqZ+fQ496oTtjsZdndrhAkrg q6qXpn7Pi7xNb1hvGCmEK3pwaIpOLfHAHyYxUk83G2vBra+SCwQkHztLAaciY/8M OG0EUvOlRHLerJm/O1ced/VgqANhhXRFj6VYyIrnFODaAcITKMTBaOx+bpoTZP7X 3836BW18nxAGFG616zG5n0O+gsxXywFKYUSXWEjHL2MiIKXN20Pt80uIkfzPxORZ B1xD51YgYsMsGuZ8gttQlLcAjavxH42AV6Oiuu5V1MxS3pLKpYfK2AIsutL3rcXk +IfvjVaLvFstxEA6k4tD =A9mH -----END PGP SIGNATURE----- --rQ2U398070+RC21q--