"struct pci_bus" related query

[vidyut karan <kvidyut2000@xxxxxxxxxxx>]

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?

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.

 

Regards

Karan V

 

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