From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chase Douglas Subject: Re: [PATCH v2] Input: evdev - Add EVIOC mechanism to extract the MT slot state Date: Fri, 06 Jan 2012 11:34:06 -0800 Message-ID: <4F074CAE.7010205@canonical.com> References: <1325863019-2242-1-git-send-email-rydberg@euromail.se> <20120106181845.GA22653@core.coreip.homeip.net> <20120106185544.GB2795@polaris.bitmath.org> <20120106191835.GA2998@polaris.bitmath.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from youngberry.canonical.com ([91.189.89.112]:39239 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754651Ab2AFTcm (ORCPT ); Fri, 6 Jan 2012 14:32:42 -0500 In-Reply-To: <20120106191835.GA2998@polaris.bitmath.org> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Henrik Rydberg Cc: Dmitry Torokhov , Benjamin Tissoires , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org On 01/06/2012 11:18 AM, Henrik Rydberg wrote: > On Fri, Jan 06, 2012 at 07:55:44PM +0100, Henrik Rydberg wrote: >>> 2 different processes should be fine; the problem would be if 2 threads >>> of the same process share the same file descriptor. So far the rest of >>> evdev copes just fine with multiple threads using the same fd (all >>> operations are atomic in this regard), setting ABS_MT_SLOT before >>> fetching the state break this property. >> >> Are we talking about the need for a per-client mutex, or something >> more subtle, like introducing indirect coupling between threads >> through per-client states? The former ought to be easily remedied. > > Ok, maybe not to so easy after all, which probably answers my own > question. Looks like a EVIOCGMTSLOT, taking both slot and event code > as argument, would be the cleaner route to take. Another ioctl, how do we > feel about that? What's the problem with userspace locking? -- Chase