From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Torokhov Subject: Re: [PATCH] cmpc_acpi: Added support for Classmate PC ACPI devices. Date: Thu, 1 Oct 2009 09:38:57 -0700 Message-ID: <20091001163857.GB22320@core.coreip.homeip.net> References: <1254188280-29155-1-git-send-email-cascardo@holoscopio.com> <9b2b86520909290220g6b5f6beal6337b17f1bdd339@mail.gmail.com> <20090929141618.GD18847@vespa.holoscopio.com> <9b2b86520909290941g6295ba36i907dfda62b968529@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from fg-out-1718.google.com ([72.14.220.157]:45232 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753597AbZJAQjG (ORCPT ); Thu, 1 Oct 2009 12:39:06 -0400 Content-Disposition: inline In-Reply-To: <9b2b86520909290941g6295ba36i907dfda62b968529@mail.gmail.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Alan Jenkins Cc: Thadeu Lima de Souza Cascardo , linux-kernel@vger.kernel.org, len.brown@intel.com, don@syst.com.br, linux-acpi@vger.kernel.org, linux-input@vger.kernel.org On Tue, Sep 29, 2009 at 05:41:42PM +0100, Alan Jenkins wrote: > On 9/29/09, Thadeu Lima de Souza Cascardo wrote: > > >> > +static void cmpc_tablet_idev_init(struct input_dev *inputdev) > >> > +{ > >> > + set_bit(EV_SW, inputdev->evbit); > >> > + set_bit(SW_TABLET_MODE, inputdev->swbit); > >> > >> Don't you need to initialize the switch value here? > >> > > > > No, input_allocate_device does kzalloc. Otherwise, this would apply to > > the other bitmaps as well. > > The other bitmaps aren't for switches though. Here's what prompted > this comment - a snippet from the old (2.6.29) version of > Documentation/rfkill.txt: > > "2. Input device switches (sources of EV_SW events) DO store their current state > (so you *must* initialize it by issuing a gratuitous input layer event on > driver start-up and also when resuming from sleep), and that state CAN be > queried from userspace through IOCTLs." > There is a mixup betweeb capabilieies and state bitmasks. In init you set up the capabilitis bits and you don't need to clear bitmaps. This is true for everything - keys/buttons, switches, relatixe/absolute axis, everything. Now switches do naturally have a certain state. Unlke keys (which are assumed to be normally in released state) switch can be on or off. So the driver has (if it can) query the switch state (hardware state) and issue appropriate input_event() to bring internal state of the device in sync with the state of the hardware. The same on resume - the switch may be altered while the box was asleep to upon resume we need to do the same. -- Dmitry