From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760571AbZKZOqQ (ORCPT ); Thu, 26 Nov 2009 09:46:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760559AbZKZOqI (ORCPT ); Thu, 26 Nov 2009 09:46:08 -0500 Received: from mail-yw0-f182.google.com ([209.85.211.182]:35408 "EHLO mail-yw0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754648AbZKZOqF convert rfc822-to-8bit (ORCPT ); Thu, 26 Nov 2009 09:46:05 -0500 MIME-Version: 1.0 In-Reply-To: References: <20091125082603.25618.57438.sendpatchset@rxone.opensource.se> From: Grant Likely Date: Thu, 26 Nov 2009 07:45:51 -0700 X-Google-Sender-Auth: 3b3c3b7e68fc7ac1 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 On Thu, Nov 26, 2009 at 12:50 AM, Magnus Damm wrote: > On Thu, Nov 26, 2009 at 4:21 PM, Grant Likely wrote: >> On Wed, Nov 25, 2009 at 11:47 PM, Magnus Damm wrote: >>> 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. > > Sure, I plan on posting a V2 of the MSIOF driver. I plan to keep the > dummy txrx_word() function for now - this to disconnect the cleanup > from the driver integration, hope that sounds like a good plan. Works for me. Now I just need to find someone with the time to refactor spi-bitbang. :-) g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd.