From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Torokhov Subject: Re: [PATCH v2] Input: evdev - Add EVIOC mechanism to extract the MT slot state Date: Fri, 6 Jan 2012 12:03:33 -0800 Message-ID: <20120106200332.GC23619@core.coreip.homeip.net> 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> <4F074CAE.7010205@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-tul01m020-f174.google.com ([209.85.214.174]:59603 "EHLO mail-tul01m020-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758895Ab2AFUDl (ORCPT ); Fri, 6 Jan 2012 15:03:41 -0500 Content-Disposition: inline In-Reply-To: <4F074CAE.7010205@canonical.com> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Chase Douglas Cc: Henrik Rydberg , Benjamin Tissoires , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org On Fri, Jan 06, 2012 at 11:34:06AM -0800, Chase Douglas wrote: > 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? It relies on userspace? ;) -- Dmitry