linux-kernel - Re: [PATCH 10/11] pciehp: add support for bridge resource reallocation

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Message-ID: <20100117093418.6d545b43@jbarnes-piketon>
Date:	Sun, 17 Jan 2010 09:34:18 -0800
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
Cc:	Yinghai Lu <yinghai@...nel.org>, Alex Chiang <achiang@...com>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 10/11] pciehp: add support for bridge resource
 reallocation

On Sat, 16 Jan 2010 16:14:31 -0700
Bjorn Helgaas <bjorn.helgaas@...com> wrote:

> On Sat, 2010-01-16 at 01:34 -0800, Yinghai Lu wrote:
> > On 01/15/2010 08:59 PM, Alex Chiang wrote:
> > > * Yinghai Lu <yinghai@...nel.org>:
> > >> From: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
> > >>
> > >> With this patch, pciehp driver try to clear PCI bridge resources
> > >> to parent bridge (root port or switch downstream port) of the
> > >> slot
> > >>
> > >> so we can shrink pci bridge resource for those port
> > >>
> > >> This feature is enabled when 'pciehp_realloc' option is
> > >> specified.
> > >>
> > >> -v2: make it could be appiled after Yinghai patchset that touch
> > >> pci bridge resource also remove poweron check, because
> > >> pci_bridge_release_res will check child at first
> > > 
> > > Same comment as my earlier patch. Why not just make this the
> > > default behavior, instead of introducing yet another command line
> > > parameter for users to guess at?
> > 
> > it will break Eric's setup/
> 
> I think this is a clue that we don't understand the problem well
> enough yet.
> 
> I'm opposed to adding kernel parameters for this sort of thing.  It is
> unreasonable to expect users to figure out whether they need to use
> this parameter or not.
> 
> Special-case switches like this make it much harder to maintain the
> code in the future.

Agreed.  Yinghai, what's wrong in the new reassignment code that
causes Eric's setup to break?  Can we just fix that instead and enable
reallocation by default?

-- 
Jesse Barnes, Intel Open Source Technology Center
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