Re: "struct pci_bus" related query

[Greg KH <greg@xxxxxxxxx>]

On Fri, Dec 02, 2005 at 11:50:59AM +0000, vidyut karan wrote:
> Hi All,
>   There are certain fields in "struct pci_bus" in linux 2.6.14 which i am not able to understand. I have listed only the relavant fields.
>   struct pci_bus {
>        ..............
>          ..............
>          struct pci_dev  *self;          /* bridge device as seen by parent */
>        ..............
>           unsigned char   primary;        /* number of primary bridge */
>         unsigned char   secondary;      /* number of secondary bridge */
>         unsigned char   subordinate;    /* max number of subordinate buses */
>           ...............
>   };
> 
> there are refernce to "bridges" in comments. Which bus does this
> "struct pci_bus" describe, the primary bus of a bridge or the
> secondary bus?

This specific pci bus device.

> Also as commented "primary" is the number of primary bridge. Please
> explain what  is meant by "primary bridge" with respect to a bus.
> Similarly for "secondary" field.

I think the PCI spec explains these fields, please see that for details.

thanks,

greg k-h

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