From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762993AbYBTRzb (ORCPT ); Wed, 20 Feb 2008 12:55:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756811AbYBTRzG (ORCPT ); Wed, 20 Feb 2008 12:55:06 -0500 Received: from mail.hevs.ch ([153.109.23.10]:52690 "EHLO mail.hevs.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761395AbYBTRzE (ORCPT ); Wed, 20 Feb 2008 12:55:04 -0500 From: Marc Pignat Organization: HEVs To: Atsushi Nemoto Subject: Re: [PATCH] atmel_spi: support zero length transfer Date: Wed, 20 Feb 2008 18:55:01 +0100 User-Agent: KMail/1.9.7 Cc: Haavard Skinnemoen , David Brownell , spi-devel-general@lists.sourceforge.net, linux-kernel@vger.kernel.org References: <20080221.005432.07645461.anemo@mba.ocn.ne.jp> In-Reply-To: <20080221.005432.07645461.anemo@mba.ocn.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset="ansi_x3.4-1968" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200802201855.02605.marc.pignat@hevs.ch> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! On Wednesday 20 February 2008, you wrote: > A spi transfer with zero length is not invalid. Such transfer can be > used to achieve delay before first CLK edge after chipselect assertion. How long will be that delay? If they are really users of that kind of thing, this should be fixed by adding a "delay_us_before_xfer" field in the struct spi_transfer. Have you tested it? I think if you start a transfer with 0 len, the ENDRX bit will never rise, however, I'm not sure about this. Regards Marc