linux-kernel - Re: Is the change to IDE probing really necessary?

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Message-ID: <20081124225139.GA26953@gollum.tnic>
Date:	Mon, 24 Nov 2008 23:51:39 +0100
From:	Borislav Petkov <petkovbb@...glemail.com>
To:	Mel Gorman <mel@....ul.ie>, bzolnier@...il.com
Cc:	sshtylyov@...mvista.com, alan@...rguk.ukuu.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: Is the change to IDE probing really necessary?

Hi,

On Mon, Nov 24, 2008 at 03:56:32PM +0000, Mel Gorman wrote:
> Hi,
> 
> I got caught by commit 20df429dd6671804999493baf2952f82582869fa as I didn't
> immediately guess that "ide_generic." was necessary on the kernel command line
> when compiled in instead of as a module. While it didn't catch me for long,
> my concern is that this is going to trip up other people with old machines
> that need that mask.  This change was introduced in 2.6.28-rc1 but I didn't
> catch it till now as I hadn't used the laptop in a while.
> 
> I have a few questions on the commit.
> 
> 1. Why was it necessary to disable the legacy probes like this at all?
> Would it be possible to try the probe_mask in the event nothing is found
> or does that have other consequences?

take a look at 0cbccbc30a60ff60dbeb203154f1f527c632de9b for background
info on the decision behind the probe_mask. Now ide-generic probes only
the legacy ports as is the case in common machine configurations and
is a sort-of fall-back option in case there's no PCI IDE controller
present. In addition, the Kconfig text explains more why ide-generic
should not be used in modern systems (not sharing IRQs, preventing
controller-specific drivers from attaching in certain cases).

And the probing _is_ done when loaded as a module so the problem is
not with the mask - in your case the probing will work just fine as
you need ide0 and ide1, AFAICT. The problem is that the probing is not
being done when ide-generic is compiled in and is the only controller
driver enabled. The only trick I can think of off the top of my head
is a Kconfig-option enabling ide-generic only when no other controller
driver is enabled and getting rid of the possibility of compiling it as
a module.

Bart, I'm sure you have a better idea :).

-- 
Regards/Gruss,
    Boris.
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