Subject: Re: NET: Questions about supporting older kernel's with kmods
From: Ben Hutchings <bhutchings@solarflare.com>
To: Gregory Haskins <gregory.haskins@gmail.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
In-Reply-To: <4B055479.8070101@gmail.com>
References: <4B055479.8070101@gmail.com>
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Organization: Solarflare Communications
Date: Thu, 19 Nov 2009 14:53:13 +0000
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On Thu, 2009-11-19 at 09:21 -0500, Gregory Haskins wrote:
> Hi All,
> 
> So I was in the process of packaging up my venet driver so that it could
> not only support the in-tree build (in -next), but also build as a KMP
> for inclusion in existing distros that already shipped (like SLE, RHEL,
> CentOS, etc).
> 
> The problem I ran into is that the ethtool and netdev_ops components of
> the in-tree version do not necessarily align with the substrate
> capabilities of older kernels.  What are the best-practices surrounding
> this issue?
>
> Q1) Is there any official CONFIG tags (e.g. HAVE_NETDEV_OPS) I can key
> off of,

These feature test macros are not consistently provided.

> or should I simply look at the kernel version?

That works up to a point, but the 'enterprise' distros backport a lot to
earlier kernel versions which can make version tests invalid.

Some out-of-tree/backported drivers use autoconf-style tests, but there
is no standard way of doing this.

﻿[...]
> Q2) Is it considered "bad form" to include such compile-time directives
> in the version of the code going upstream?
[...]

Yes.  Don't do that.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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