Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261716AbVAZXnO (ORCPT ); Wed, 26 Jan 2005 18:43:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261322AbVAZXla (ORCPT ); Wed, 26 Jan 2005 18:41:30 -0500 Received: from rproxy.gmail.com ([64.233.170.198]:27759 "EHLO rproxy.gmail.com") by vger.kernel.org with ESMTP id S261368AbVAZSa2 (ORCPT ); Wed, 26 Jan 2005 13:30:28 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:references; b=TlVO/gTSWlsGJo8urcHU5VlNX8frAmqhoNExoCtiE54y0dOVlNMS+MUyQ/1kLp5smWI1kgHcOTdPGybCzluv2fHEAotrzSC/S6GvpAlZNagzcEAWsXxvqdLYcCvsf+FXqA19bo0mgHQHLYbls0jIaJEMeeOm/09WB69XsQoh8Sw= Message-ID: Date: Wed, 26 Jan 2005 13:30:28 -0500 From: Dmitry Torokhov Reply-To: dtor_core@ameritech.net To: linux-os@analogic.com Subject: Re: i8042 access timings Cc: Vojtech Pavlik , linux-input@atrey.karlin.mff.cuni.cz, Alan Cox , linux-kernel@vger.kernel.org In-Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit References: <200501250241.14695.dtor_core@ameritech.net> <20050126154307.GB4422@ucw.cz> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1742 Lines: 44 On Wed, 26 Jan 2005 12:05:47 -0500 (EST), linux-os wrote: > On Wed, 26 Jan 2005, Dmitry Torokhov wrote: > > > On Wed, 26 Jan 2005 16:43:07 +0100, Vojtech Pavlik wrote: > >> On Tue, Jan 25, 2005 at 02:41:14AM -0500, Dmitry Torokhov wrote: > >>> @@ -213,7 +217,10 @@ > >>> if (!retval) > >>> for (i = 0; i < ((command >> 8) & 0xf); i++) { > >>> if ((retval = i8042_wait_read())) break; > >>> - if (i8042_read_status() & I8042_STR_AUXDATA) > >>> + udelay(I8042_STR_DELAY); > >>> + str = i8042_read_status(); > >> [] > >>> + udelay(I8042_DATA_DELAY); > >>> + if (str & I8042_STR_AUXDATA) > >>> param[i] = ~i8042_read_data(); > >>> else > >>> param[i] = i8042_read_data(); > >> > >> We may as well drop the negation. It's a bad way to signal the data came > >> from the AUX port. Then we don't need the extra status read and can just > >> proceed to read the data, since IMO we don't need to wait inbetween, > >> even according to the IBM spec. > > > > Do you remember why it has been done to begin with? > > > > -- > > Dmitry > > > The only time you need any delay at all is after you have send ... Thank you Richard for this thorough explanation of IO access but I was actually asking why we wanted to invert AUX data. -- Dmitry - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/