Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752634AbaG1Rp2 (ORCPT ); Mon, 28 Jul 2014 13:45:28 -0400 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:59908 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751432AbaG1RpW (ORCPT ); Mon, 28 Jul 2014 13:45:22 -0400 Date: Mon, 28 Jul 2014 18:44:10 +0100 From: Mark Brown To: Olof Johansson Cc: Graeme Gregory , Mark Rutland , Catalin Marinas , Will Deacon , Lv Zheng , Lorenzo Pieralisi , Daniel Lezcano , Robert Moore , "linux-acpi@vger.kernel.org" , Grant Likely , Charles Garcia-Tobin , Robert Richter , Jason Cooper , Arnd Bergmann , Marc Zyngier , Liviu Dudau , Bjorn Helgaas , "linux-arm-kernel@lists.infradead.org" , Randy Dunlap , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , Hanjun Guo , Sudeep Holla Message-ID: <20140728174410.GD17528@sirena.org.uk> References: <1406206825-15590-1-git-send-email-hanjun.guo@linaro.org> <1406206825-15590-20-git-send-email-hanjun.guo@linaro.org> <53D60D11.8050205@linaro.org> <20140728162340.GA32359@quad.lixom.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="TCJSbVjzg7MjJqGR" Content-Disposition: inline In-Reply-To: <20140728162340.GA32359@quad.lixom.net> X-Cookie: 98% lean. User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: 94.175.94.161 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: Re: [PATCH 19/19] Documentation: ACPI for ARM64 X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on mezzanine.sirena.org.uk) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --TCJSbVjzg7MjJqGR Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, Jul 28, 2014 at 09:23:40AM -0700, Olof Johansson wrote: > On Mon, Jul 28, 2014 at 09:42:57AM +0100, Graeme Gregory wrote: > > >>+On no account should a Device Tree attempt to be replicated in ASL using such > > >>+constructs as Name(KEY0, "Value1") type constructs. Additional driver specific > > >>+data should be passed in the appropriate _DSM (ACPI Section 9.14.1) method or > > >>+_DSD (ACPI Section 6.2.5). This data should be rare and not OS specific. ... > > >I see these two sentences as contradictory, given that the _DSD doc > > >worst case turn into quite a mess. > > >Given that ACPI can present completely different data based on what OS > > >is running, it's quite common to indeed have OS specific data in > > >there. How does that relate to this document and these practices? > > OS specific data has traditionally not worked out well for ACPI, I > > would like to "persuade" people not to use it on ARM. > It hasn't? I think Microsoft disagrees. It's also how vendors have been able to > present an older machine description to keep their newer hardware compatible > with older software, isn't it? How do you expect to handle that if you can > only present one table? It's the same challenge that DT has. It seems sensible to recommend against using OS specifics if possible if only from the point of view of improving the robustness of the system - the less paths there are to test in the BIOS the more likely it is that the active path is one that's been well tested. It's legal in the spec and you can do it but encouraging people not to do it will hopefully make life easier down the line. Similarly encouraging people to put as little as possible in there should reduce the opportunities they have to get things wrong. The best use case for OS testing is to enable a non-default workaround for older versions of the OS but in the case of Linux that's a bit tricky since we don't have clear versions to test against - even with the kernel version number it's never clear if it's been patched by a distro or something. Windows is a much more fixed target here. --TCJSbVjzg7MjJqGR Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBAgAGBQJT1ovnAAoJELSic+t+oim9ii8P/3ThrFfXf5feXkDPmK24Wis0 igV/LE7WNK+i2D36rUn8Gm5KpkKoRDd3dcRw1V79s6+1ezfJc4AqGXCLQHQ9k5Mp uY3GxRpUCTemN61dlrO2T/vS6Jy4jvacxcOZ4PYUc+EcEXncEQIDoYq0JgA9iPVs parp50FIxjQauOT6MiXo61h/JgIb/05zyFogyvu8QHHNpFEne27VU0uYAXWISJww B+lErnZf7s/SialvKPteyds3+IEibN22G9/VvPGXhtQOELhL7PF6hE9erCeiwtku PLJ4jdeQNuZEsO2gAz1fpPI3+gIJMY6Q5CwB1AXpqVBo7gQWo157NY9P03+kKQaY aIHJw3eUTQqc1BK06vd5DCYec40Rk4KceeheWDcW38WSB34g1Btqwjnx0DzzDA7E W/UXant9mWcpOQgfrCjaru1zwD6HTzvL2VtoYflPUOaG7ioTqd5w1c91HCmEBrre B6LNvTzfT0BJd50kdAHWjgUjnQZsYv2iLxaBIytpjAN/FJN5jKdwzvLojvkkNuQS qrQ6yn8HhWq6yVLgbRLhbs92OK1cr2wgHE912OxPQadBJv8WqZgQAaifmGUx+xMW 1LgjHWasrWI+hDcImzrsB0yzSbKeUhhHtu02S/pFErtGd+2Y2dSGYvTUCoZ2IaEX cl2YG17TrpAUOT/+xO8E =iUQH -----END PGP SIGNATURE----- --TCJSbVjzg7MjJqGR-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/