linux-kernel - Re: [PATCH] PCI: conditional resource-reallocation through kernel parameter pci=realloc

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Message-ID: <CAErSpo6=c0C-+SbJjFPQFNM3u1pFNZ0TogcwB+takiprUpkM4w@mail.gmail.com>
Date:	Thu, 30 Jun 2011 14:24:24 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Ram Pai <linuxram@...ibm.com>
Cc:	Oliver Hartkopp <socketcan@...tkopp.net>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	torvalds@...ux-foundation.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, yinghai@...nel.org
Subject: Re: [PATCH] PCI: conditional resource-reallocation through kernel
 parameter pci=realloc

On Thu, Jun 30, 2011 at 12:38 PM, Ram Pai <linuxram@...ibm.com> wrote:
> On Thu, Jun 30, 2011 at 07:12:38PM +0200, Oliver Hartkopp wrote:
>> On 30.06.2011 19:07, Jesse Barnes wrote:
>> > On Thu, 30 Jun 2011 19:04:55 +0200
>> > Oliver Hartkopp <socketcan@...tkopp.net> wrote:
>> >
>> >> On 30.06.2011 10:09, Ram Pai wrote:
>> >>> Multiple attempts to dynamically reallocate pci resources have unfortunately
>> >>> lead to regressions. Though we continue to fix the regressions and fine tune the
>> >>> dynamic-reallocation behavior, we have not reached a acceptable state yet.
>> >>>
>> >>> This patch provides a interim solution. It disables dynamic-reallocation; by
>> >>> default, with the ability to enable it through pci=realloc kernel command line
>> >>> parameter.
>> >>
>> >> What is the advantage of creating an 'interim' kernel parameter instead of
>> >> reverting the problematic commit and queue up a proper solution for 3.1 ?
>> >>
>> >> A kernel parameter needs to be observed, documented and set appropriately.
>> >>
>> >> I would prefer to have an automatic solution - if not in 3.0 then in 3.1 ...
>> >
>> > Yeah, we all want an automatic solution, but we still haven't been able
>> > to achieve one.  My hope is that a parameter will let us keep the code
>> > upstream for Ram and others to keep fixing, then we can move to using
>> > it by default in some future release.  Keeping the code upstream but
>> > behind a param should make development easier; at least that's the goal.
>>
>> What's wrong with the "[PATCH 0/4 v2] PCI: fix cardbus and sriov regressions"?
>> To me it looked good - or don't you trust that fix right now?
>
> I trust the fix :).
>
> Linus's concern was the wrong alignment, which I have fixed, but yet to resend
> the patchset. Will do today.
>
> However Linus's other concern was "too late for 3.0.0, for such a large patch".
>
> There is the other concern about "should cardbus resources be treated nice-to-have?"

Somewhere along the way, can we get rid of the awkward "nice-to-have"
language?  I think "optional" conveys most of the intended meaning,
perhaps lacking the shade that "we'll allocate them if we can."  But
the important part is that they are not *required*, and "optional" is
a nice antonym for "required."

Bjorn
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