From mboxrd@z Thu Jan 1 00:00:00 1970 From: ville.syrjala@linux.intel.com (Ville =?iso-8859-1?Q?Syrj=E4l=E4?=) Date: Mon, 19 Nov 2012 16:32:36 +0200 Subject: [PATCH] ARM: add get_user() support for 8 byte types In-Reply-To: <201211151439.41393.arnd@arndb.de> References: <1352495853-9790-1-git-send-email-rob.clark@linaro.org> <201211151339.08016.arnd@arndb.de> <201211151439.41393.arnd@arndb.de> Message-ID: <20121119143236.GA3296@intel.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Nov 15, 2012 at 02:39:41PM +0000, Arnd Bergmann wrote: > On Thursday 15 November 2012, Rob Clark wrote: > > > 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? > > > > well, it is mostly because it seemed like a good idea to first try to > > solve the root issue, rather than having to fix things up in each > > driver when someone from x86-world introduces a 64b get_user().. > > As pointed out by hpa earlier, x86-32 doesn't have a 64b get_user > either. I don't think we have a lot of drivers that are used only > on 64-bit x86 and on 32-bit ARM but not on 32-bit x86. Ouch. I didn't realize that x86-32 doesn't have it. All the systems where I've run the new code are 64bit so I never noticed the problem. I see there was a patch [1] posted a long time ago to implement 64bit get_user() on x86-32. I wonder what happened to it? [1] https://lkml.org/lkml/2004/4/20/96 -- Ville Syrj?l? Intel OTC