Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753076AbZKZHVo (ORCPT ); Thu, 26 Nov 2009 02:21:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751462AbZKZHVo (ORCPT ); Thu, 26 Nov 2009 02:21:44 -0500 Received: from mail-gx0-f226.google.com ([209.85.217.226]:34125 "EHLO mail-gx0-f226.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751350AbZKZHVn convert rfc822-to-8bit (ORCPT ); Thu, 26 Nov 2009 02:21:43 -0500 MIME-Version: 1.0 In-Reply-To: References: <20091125082603.25618.57438.sendpatchset@rxone.opensource.se> From: Grant Likely Date: Thu, 26 Nov 2009 00:21:29 -0700 X-Google-Sender-Auth: 6e0ab085b1387b67 Message-ID: Subject: Re: [PATCH] spi: Allow using spi_bitbang_setup() with custom txrx_bufs() To: Magnus Damm Cc: spi-devel-general@lists.sourceforge.net, dbrownell@users.sourceforge.net, linux-kernel@vger.kernel.org, akpm@linux-foundation.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2000 Lines: 45 On Wed, Nov 25, 2009 at 11:47 PM, Magnus Damm wrote: > Hi Grant, > > On Thu, Nov 26, 2009 at 7:15 AM, Grant Likely wrote: >> On Wed, Nov 25, 2009 at 1:26 AM, Magnus Damm wrote: >>> ? ? ? ?/* per-word shift register access, in hardware or bitbanging */ >>> - ? ? ? cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)]; >>> - ? ? ? if (!cs->txrx_word) >>> - ? ? ? ? ? ? ? return -EINVAL; >>> + ? ? ? if (bitbang->txrx_bufs == spi_bitbang_bufs) { >>> + ? ? ? ? ? ? ? cs->txrx_word = bitbang->txrx_word[spi->mode & mode_mask]; >>> + ? ? ? ? ? ? ? if (!cs->txrx_word) >>> + ? ? ? ? ? ? ? ? ? ? ? return -EINVAL; >>> + ? ? ? } >> >> Hmmm... this smells like an ugly hack to me. ?It seems to me that if >> some bitbang backend drivers don't want this code, then it should be >> encoded into a callback so it can be overridden. ?Thoughts. > > Yeah, it's far from clean. I want to make use of spi_bitbang_setup() > in my MSIOF driver, but I want to avoid dummy txtx_word[] callbacks > that will be unused since i'm using a driver specific > bitbang->txrx_bufs function. > > I guess the attached patch is slightly cleaner? I like the idea of > letting bitbang drivers use shared code for > spi_bitbang_setup()/spi_bitbang_cleanup() with their private > setup_transfer() function which in turn calls > spi_bitbang_setup_transfer(). My impression is that there's quite a > bit of duplicated setup()/cleanup() code. This is certainly less ugly. But with the points brought up in the other thread, I want to have a close look at spi-bitbang before I start applying stuff. It seems nasty. Give me a few days. g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. -- 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/