linux-kernel - Re: One problem in reassign pci bus number?

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Message-ID: <CAE9FiQUU+a4yQJTiud=aYx2xXcoQZpH2rJyVhj19TQKGN7=2BA@mail.gmail.com>
Date:	Mon, 7 May 2012 20:42:59 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Richard Yang <weiyang@...ux.vnet.ibm.com>
Cc:	Wei Yang <weiyang.kernel@...il.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: One problem in reassign pci bus number?

On Mon, May 7, 2012 at 7:46 PM, Richard Yang <weiyang@...ux.vnet.ibm.com> wrote:
> On Sun, May 06, 2012 at 07:04:09PM -0700, Yinghai Lu wrote:
>>On Sun, May 6, 2012 at 6:17 PM, Richard Yang <weiyang@...ux.vnet.ibm.com> wrote:
>>> so this free space will be combined with the free space got from
>>> parent, form a big space to meet the requirement.
>>>
>>> This is the general idea about probe_resource()?
>>>
>>> And this is the design decision to find the free space at the end
>>> of top, even at the start we have more free space?
>>
>>no, probe_resource will get from start if space is big enough.
>>
>>if not, it will try to extend top.
>
> Hmm... for example we still have this
>               parent[70-160]
> brother1[70-80]  res[90-150]  brother2[151-160]
>                   ->child[105-140]
>
> if we call probe_resource(res, new_res, 16, par, 1, 0xff,
> IORESOURCE_PCI_FIXED);
>
> I think this call is used to allocate a res of size 16 under res.
> When there is no enough free space, it will expend res, and res->parent.
>
> While in this situation, res doesn't have enough free space. so it need
> to expend itself.
>
> In the probe_resource() it tries to extend res on the right side.
> So even there is enough space between brother1 and res, I think the
> probe_resource() will not return 0.
>
> Do you think my analysis is correct?

it will reduce needed size one by one. so at last it will return
[91, 104]

Yinghai
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