Re: One problem in reassign pci bus number?
From: Yinghai Lu
Date: Mon May 14 2012 - 01:40:47 EST
On Sun, May 13, 2012 at 6:55 PM, Richard Yang
<weiyang@xxxxxxxxxxxxxxxxxx> wrote:
> On Mon, Apr 23, 2012 at 03:46:03PM -0400, Don Dutile wrote:
>>On 04/22/2012 11:52 AM, Richard Yang 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?
>>
> Yinghai,
>
> Take my original question.
>
> B3 doesn't get the bus number, which its parent doesn't have free bus
> number and there is no gap between B1 and B2.
>
> So in this case, the probe_resource() can't find bus number for B3.
> Then cause pci_bridge_probe_busn_res() return non-zero.
>
> Then B3 couldn't work fine?
B3 is on Bus 1? B3 is the one of bridges on Bus1?
if B3 is only bridge on Bus1, it probe_resource should return [2,15]
at first, and then scan B3.
Yinghai
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