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Re: PCI-enum and SouthBridge behaviour...

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On 25/07/2016 13:06, wolfgang kern wrote:
> James Harris wrote:

...

>> Early machines had motherboard or machine identification in the top
>> bytes of the ROM.
>
> isn't this methode obsolete since many years ?

You know me. ;-)


>>>> Your PCI scan won't take long, will it?
>
>>> No, only a few mS if I just scan until all desired are found, but a full
>>> scan over all possible 256 busses would take seconds.
>
>> Wouldn't you only attempt to scan a non-root PCI bus if you discover a
>> bridge to it? IIRC PCI configs for bridges give the downstream bus
>> number. So you wouldn't need to scan 256 busses unless you had a
>> veeery big machine. ;-)
>
> bridges allow communication between apart busses, but devices like USB
> hosts, sound, graphic, LAN, firewire,.. should all show up on the BUS
> where they are connected to.

(I think you mean "separate" rather than "apart".)


> While I know most details on motherboard and chipset in my machines
> including BUS-Device-Function for onchip devices, there may be a few new
> addons on the board which become configured by the BIOS. So my onboard
> sound report its PCI-config on BUS_07 and firewire on BUS_3.

I am not sure how that relates to having to scan 256 potential bus 
numbers. Can you not find slave busses as you scan?

To make an example, you might scan bus 0 and find:

  a disk controller
  a video controller
  a bridge to bus 3
  a bridge to bus 7

AIUI the PCI enumeration process would then scan busses 3 and 7.

Basically, PCI enumeration would not need to scan all 256 bus numbers 
but only those if finds bridges to.

I might be wrong. This is just from memory.


-- 
James Harris

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Thread

PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-22 21:53 +0200
  Re: PCI-enum and SouthBridge behaviour... James Harris <james.harris.1@gmail.com> - 2016-07-24 16:52 +0100
    Re: PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-24 19:54 +0200
      Re: PCI-enum and SouthBridge behaviour... James Harris <james.harris.1@gmail.com> - 2016-07-25 07:07 +0100
        Re: PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-25 11:04 +0200
          Re: PCI-enum and SouthBridge behaviour... James Harris <james.harris.1@gmail.com> - 2016-07-25 10:30 +0100
            Re: PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-25 14:06 +0200
              Re: PCI-enum and SouthBridge behaviour... James Harris <james.harris.1@gmail.com> - 2016-07-25 13:16 +0100
                Re: PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-26 13:09 +0200
                Re: PCI-enum and SouthBridge behaviour... James Harris <james.harris.1@gmail.com> - 2016-07-26 15:14 +0100
          Re: PCI-enum and SouthBridge behaviour... Rod Pemberton <NoHaveNotOne@bcczxcfrze.cam> - 2016-07-25 21:55 -0400
            Re: PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-26 12:48 +0200
  Re: PCI-enum and SouthBridge behaviour... Rod Pemberton <NoHaveNotOne@bcczxcfrze.cam> - 2016-07-26 08:18 -0400
    Re: PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-26 20:11 +0200
  Re: PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-28 18:53 +0200
    Re: PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-29 19:47 +0200
      Re: PCI-enum and SouthBridge behaviour... Rod Pemberton <NoHaveNotOne@zxdehrnyya.cam> - 2016-07-29 17:44 -0400
        Re: PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-30 09:44 +0200
    Re: PCI-enum and SouthBridge behaviour... James Harris <james.harris.1@gmail.com> - 2016-07-30 12:55 +0100
      Re: PCI-enum and SouthBridge behaviour... "wolfgang kern" <nowhere@never.at> - 2016-07-30 19:40 +0200
        Re: PCI-enum and SouthBridge behaviour... James Harris <james.harris.1@gmail.com> - 2016-07-30 19:08 +0100

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