• Bjorn Helgaas's avatar
    PNP: convert resource options to single linked list · 1f32ca31
    Bjorn Helgaas authored
    ISAPNP, PNPBIOS, and ACPI describe the "possible resource settings" of
    a device, i.e., the possibilities an OS bus driver has when it assigns
    I/O port, MMIO, and other resources to the device.
    
    PNP used to maintain this "possible resource setting" information in
    one independent option structure and a list of dependent option
    structures for each device.  Each of these option structures had lists
    of I/O, memory, IRQ, and DMA resources, for example:
    
      dev
        independent options
          ind-io0  -> ind-io1  ...
          ind-mem0 -> ind-mem1 ...
          ...
        dependent option set 0
          dep0-io0  -> dep0-io1  ...
          dep0-mem0 -> dep0-mem1 ...
          ...
        dependent option set 1
          dep1-io0  -> dep1-io1  ...
          dep1-mem0 -> dep1-mem1 ...
          ...
        ...
    
    This data structure was designed for ISAPNP, where the OS configures
    device resource settings by writing directly to configuration
    registers.  The OS can write the registers in arbitrary order much
    like it writes PCI BARs.
    
    However, for PNPBIOS and ACPI devices, the OS uses firmware interfaces
    that perform device configuration, and it is important to pass the
    desired settings to those interfaces in the correct order.  The OS
    learns the correct order by using firmware interfaces that return the
    "current resource settings" and "possible resource settings," but the
    option structures above doesn't store the ordering information.
    
    This patch replaces the independent and dependent lists with a single
    list of options.  For example, a device might have possible resource
    settings like this:
    
      dev
        options
          ind-io0 -> dep0-io0 -> dep1->io0 -> ind-io1 ...
    
    All the possible settings are in the same list, in the order they
    come from the firmware "possible resource settings" list.  Each entry
    is tagged with an independent/dependent flag.  Dependent entries also
    have a "set number" and an optional priority value.  All dependent
    entries must be assigned from the same set.  For example, the OS can
    use all the entries from dependent set 0, or all the entries from
    dependent set 1, but it cannot mix entries from set 0 with entries
    from set 1.
    
    Prior to this patch PNP didn't keep track of the order of this list,
    and it assigned all independent options first, then all dependent
    ones.  Using the example above, that resulted in a "desired
    configuration" list like this:
    
      ind->io0 -> ind->io1 -> depN-io0 ...
    
    instead of the list the firmware expects, which looks like this:
    
      ind->io0 -> depN-io0 -> ind-io1 ...
    Signed-off-by: default avatarBjorn Helgaas <bjorn.helgaas@hp.com>
    Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
    Acked-by: default avatarRene Herman <rene.herman@gmail.com>
    Signed-off-by: default avatarLen Brown <len.brown@intel.com>
    1f32ca31
interface.c 10.6 KB