From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH] ARM: add get_user() support for 8 byte types Date: Thu, 15 Nov 2012 13:39:07 +0000 Message-ID: <201211151339.08016.arnd@arndb.de> References: <1352495853-9790-1-git-send-email-rob.clark@linaro.org> <201211150919.37343.arnd@arndb.de> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Rob Clark Cc: Russell King - ARM Linux , linux-arm-kernel@lists.infradead.org, patches@linaro.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, dri-devel@lists.freedesktop.org List-Id: linux-omap@vger.kernel.org On Thursday 15 November 2012, Rob Clark wrote: > On Thu, Nov 15, 2012 at 3:19 AM, Arnd Bergmann wrote: > > On Tuesday 13 November 2012, Russell King - ARM Linux wrote: > >> You're missing something; that is one of the greatest powers of open > >> source. The many eyes (and minds) effect. Someone out there probably > >> has a solution to whatever problem, the trick is to find that person. :) > >> > >> I think we have a working solution for this for ARM. It won't be suitable > >> for every arch, where they have 8-bit and 16-bit registers able to be > >> allocated by the compiler, but for architectures where the minimum register > >> size is 32-bit, what we have below should work. > > > > I don't mind at all adding the extension to ARM, and I think it's pretty > > cool that you guys actually found a working solution. > > > > The part that worries me is that we are making architecture independent > > code depend on a clever hack that may or may not be possible to implement > > on a given architecture, and that most architecture maintainers wouldn't > > know how to implement correctly even if it's possible. > > I could always send a 3rd version with a comment smashed on about why > that works if you think this is a problem.. Comments are always good, so I'd surely like to see those get added. As I said, I don't have any objections to the addition of your patch to the ARM code, which sounds useful to have. I still haven't heard a conclusive argument why we need to use get_user() rather than copy_from_user() in the DRM code. Is this about a fast path where you want to shave off a few cycles for each call, or does this simplify the code structure, or something else? Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Thu, 15 Nov 2012 13:39:07 +0000 Subject: [PATCH] ARM: add get_user() support for 8 byte types In-Reply-To: References: <1352495853-9790-1-git-send-email-rob.clark@linaro.org> <201211150919.37343.arnd@arndb.de> Message-ID: <201211151339.08016.arnd@arndb.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thursday 15 November 2012, Rob Clark wrote: > On Thu, Nov 15, 2012 at 3:19 AM, Arnd Bergmann wrote: > > On Tuesday 13 November 2012, Russell King - ARM Linux wrote: > >> You're missing something; that is one of the greatest powers of open > >> source. The many eyes (and minds) effect. Someone out there probably > >> has a solution to whatever problem, the trick is to find that person. :) > >> > >> I think we have a working solution for this for ARM. It won't be suitable > >> for every arch, where they have 8-bit and 16-bit registers able to be > >> allocated by the compiler, but for architectures where the minimum register > >> size is 32-bit, what we have below should work. > > > > I don't mind at all adding the extension to ARM, and I think it's pretty > > cool that you guys actually found a working solution. > > > > The part that worries me is that we are making architecture independent > > code depend on a clever hack that may or may not be possible to implement > > on a given architecture, and that most architecture maintainers wouldn't > > know how to implement correctly even if it's possible. > > I could always send a 3rd version with a comment smashed on about why > that works if you think this is a problem.. Comments are always good, so I'd surely like to see those get added. As I said, I don't have any objections to the addition of your patch to the ARM code, which sounds useful to have. I still haven't heard a conclusive argument why we need to use get_user() rather than copy_from_user() in the DRM code. Is this about a fast path where you want to shave off a few cycles for each call, or does this simplify the code structure, or something else? Arnd