From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH 00/68] ide2libata Date: Fri, 29 Jan 2010 16:40:47 -0500 Message-ID: <4B6355DF.9050001@garzik.org> References: <20100129160308.21495.14120.sendpatchset@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-yw0-f189.google.com ([209.85.211.189]:43117 "EHLO mail-yw0-f189.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753367Ab0A2VsI (ORCPT ); Fri, 29 Jan 2010 16:48:08 -0500 In-Reply-To: <20100129160308.21495.14120.sendpatchset@localhost> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Bartlomiej Zolnierkiewicz Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org On 01/29/2010 11:03 AM, Bartlomiej Zolnierkiewicz wrote: > Hi, > > Here is a patchset (on top of atang-v3.1 tree) applying "out-of-the-box" > thinking to duplicated libata PATA and IDE subsystem host driver sets. > Namely, it modifies IDE API slightly to match libata's one more, adds > a tiny source-code level translation layer (ide2libata.h header file > which consists of only 17 lines of code) and then converts host drivers > to use shared source code for low-level operations (all drivers have > been carefully audited during porting to minimize the probability of > adding regressions accidentally). As an end result it is much easier > to maintain both driver sets (differences between 'new'/'old' drivers > are now apparent and there is no longer a need to manually back-port > many classes of bugfixes) and over 2500 LOC are gone. Interesting. I'm fine with applying patches 2-5, but I am definitely interested to hear what others think about this. Clearly, LOC is reduced, but that's not the only factor in code maintenance. With regards to libata and old-IDE, I have always thought the ideal scenario was to leave old-IDE in bugfix-only mode, with next-to-no API or driver churn besides that which is absolutely required for the fix. En masse backporting bug fixes is what's known as a one-time cost. Once the majority of libata PATA drivers reach bugfix and feature parity, the need for code sharing is reduced greatly. The ide2libata proposal creates on-going costs, not just a one-time cost, because the old-IDE drivers will have -increased- potential for problems when a libata PATA driver is modified. Such is the -cost- of heavily intertwined code sharing. A single header change implies that two, not one, drivers might break. That weakens the "leave it alone" stability promise of old-IDE. Waiting for other comments... this patchset is not an onerous burden to libata, but I think it creates nasty cross-tree issues, potentially perturbing old-IDE. Jeff