Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754131Ab1FXSsG (ORCPT ); Fri, 24 Jun 2011 14:48:06 -0400 Received: from mail-ew0-f46.google.com ([209.85.215.46]:34493 "EHLO mail-ew0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753729Ab1FXSsD convert rfc822-to-8bit (ORCPT ); Fri, 24 Jun 2011 14:48:03 -0400 MIME-Version: 1.0 In-Reply-To: <20110624203404.7a3f6f6a@stein> References: <4E04912A.4090305@infradead.org> <201106241554.10751.hverkuil@xs4all.nl> <4E04A122.2080002@infradead.org> <20110624203404.7a3f6f6a@stein> Date: Fri, 24 Jun 2011 14:48:00 -0400 Message-ID: Subject: Re: [RFC] Don't use linux/version.h anymore to indicate a per-driver version - Was: Re: [PATCH 03/37] Remove unneeded version.h includes from include/ From: Devin Heitmueller To: Stefan Richter Cc: Mauro Carvalho Chehab , Hans Verkuil , Jesper Juhl , LKML , trivial@kernel.org, linux-media@vger.kernel.org, ceph-devel@vger.kernel.org, Sage Weil 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: 2503 Lines: 53 On Fri, Jun 24, 2011 at 2:34 PM, Stefan Richter wrote: > If the "driver version" is in fact an ABI version, then the driver author > should really increase it only when ABI behavior is changed (and only if > the behavior change can only be communicated by version number --- e.g. > addition of an ioctl is not among such reasons). ?And the author should > commit behavior changing implementation and version number change in a > single changeset. > > And anybody who backmerges such an ABI behavior change into another kernel > branch (stable, longterm, distro...) must backmerge the associated version > number change too. > > Of course sometimes people realize this only after the fact. ?Or driver > authors don't have a clear understanding of ABI versioning to begin with. > I am saying so because I had to learn it too; I certainly wasn't born > with an instinct knowledge how to do it properly. > > (Disclaimer: ?I have no stake in drivers/media/ ABIs. ?But I am involved > in maintaining a userspace ABI elsewhere in drivers/firewire/, and one of > the userspace libraries that use this ABI.) Hi Stefan, To be clear, I don't think anyone is actually proposing that the driver version number really be used as any form of formal "ABI versioning" scheme. In almost all cases, it's so the application can know to *not* do something is the driver is older than X. Given all the cases I've seen, it doesn't really hurt anything if the driver contains a fix from newer than X, aside from the fact that the application won't take advantage of whatever feature/functionality the fix made work. In other words, I think from a backport standpoint, it usually doesn't *hurt* anything if a fix is backported without the version being incremented, aside from applications not knowing that the feature/fix is present. Really, this is all about applications being able to jam a hack into their code that translates to "don't call this ioctl() with some particular argument if it's driver W less than version X, because the driver had a bug that is likely to panic the guy's PC". Sure, it's a crummy solution, but at this point it's the best that we have got. Devin -- Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com -- 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/