From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757260AbYBPOCW (ORCPT ); Sat, 16 Feb 2008 09:02:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753857AbYBPOCO (ORCPT ); Sat, 16 Feb 2008 09:02:14 -0500 Received: from mba.ocn.ne.jp ([122.1.235.107]:61797 "EHLO smtp.mba.ocn.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753901AbYBPOCO (ORCPT ); Sat, 16 Feb 2008 09:02:14 -0500 Date: Sat, 16 Feb 2008 23:02:32 +0900 (JST) Message-Id: <20080216.230232.25478328.anemo@mba.ocn.ne.jp> To: David Brownell , spi-devel-general@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: spi transfer with zero length From: Atsushi Nemoto X-Fingerprint: 6ACA 1623 39BD 9A94 9B1A B746 CA77 FE94 2874 D52F X-Pgp-Public-Key: http://wwwkeys.pgp.net/pks/lookup?op=get&search=0x2874D52F X-Mailer: Mew version 5.2 on Emacs 21.4 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi. Is it legal to use zero for 'len' field of struct spi_transfer? I mean, len=0, tx_buf=rx_buf=NULL, delay_usecs!=0. Some SPI devices need slightly long delay before first CLK edge after CS assertion. To achieve this, I think inserting using a zero length transfer before real transfers. But it seems some drivers do not handle this case properly. Is this driver's bug, or we need additional delay field in struct spi_device for such case? --- Atsushi Nemoto