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

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Message-ID: <CADLM8XNdfByjCXuEX3pmuUun_qTSZqeARO_vPGy7gc+DoOGxog@mail.gmail.com>
Date:	Tue, 24 Apr 2012 22:56:19 +0800
From:	Wei Yang <weiyang.kernel@...il.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Richard Yang <weiyang@...ux.vnet.ibm.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: One problem in reassign pci bus number?

2012/4/24 Yinghai Lu <yinghai@...nel.org>:
> On Sun, Apr 22, 2012 at 8:52 AM, Richard Yang
> <weiyang@...ux.vnet.ibm.com> wrote:
>> All,
>>
>> I am reading the pci_scan_bridge() and not sure what will happen in
>> following situation.
>>
>> Suppose the kernel is not passed the pci=assign-busses.
>>
>> Below is a picture about the pci system.
>>
>>                   +-------+
>>                   |       | root bridge(0,255)
>>                   +---+---+
>>                       |          Bus 0
>>      -----+-----------+------------------------------+--
>>           |                                          |
>>           |                                          |
>>           |                                          |
>>      +----+----+                               +-----+-----+
>>      |         |  B1(1,15)                     |           |B2(16,28)
>>      +----+----+                               +-----+-----+
>>           |  Bus 1                                   |    Bus 16
>>      -----+-----------------------         ----------+----------------
>>                            |
>>                       +----+----+
>>                       |         | B3
>>                       +---------+
>>
>> Suppose B1 and B2 works fine with the BIOS, which get the right bus
>> number and range.
>>
>> B3 does not works fine with the BIOS, which doesn't get the bus number.
>>
>> So in pci_scan_bridge(), B3 will be met in the second pass and get bus
>> number 16?
>> Would this be a conflict?
>
> busn_alloc patchset should address your concern.
>
> git://git.kernel.org/pub/scm/linux/kernel/git/yinghai/linux-yinghai.git
> for-pci-busn-alloc
>
hmm... the code changes too much...
I need more time to understanding it.

while the case i found is different from that reported by Don.

> Yinghai
> --
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-- 
Richard Yang
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