• Zhang Rui's avatar
    ACPI / PNP: use device ID list for PNPACPI device enumeration · eec15edb
    Zhang Rui authored
    ACPI can be used to enumerate PNP devices, but the code does not
    handle this in the right way currently.  Namely, if an ACPI device
    object
     1. Has a _CRS method,
     2. Has an identification of
        "three capital characters followed by four hex digits",
     3. Is not in the excluded IDs list,
    it will be enumerated to PNP bus (that is, a PNP device object will
    be create for it).  This means that, actually, the PNP bus type is
    used as the default bus type for enumerating _HID devices in ACPI.
    
    However, more and more _HID devices need to be enumerated to the
    platform bus instead (that is, platform device objects need to be
    created for them).  As a result, the device ID list in acpi_platform.c
    is used to enforce creating platform device objects rather than PNP
    device objects for matching devices.  That list has been continuously
    growing recently, unfortunately, and it is pretty much guaranteed to
    grow even more in the future.
    
    To address that problem it is better to enumerate _HID devices
    as platform devices by default.  To this end, change the way of
    enumerating PNP devices by adding a PNP ACPI scan handler that
    will use a device ID list to create PNP devices for the ACPI
    device objects whose device IDs are present in that list.
    
    The initial device ID list in the PNP ACPI scan handler contains
    all of the pnp_device_id strings from all the existing PNP drivers,
    so this change should be transparent to the PNP core and all of the
    PNP drivers.  Still, in the future it should be possible to reduce
    its size by converting PNP drivers that need not be PNP for any
    technical reasons into platform drivers.
    Signed-off-by: default avatarZhang Rui <rui.zhang@intel.com>
    [rjw: Rewrote the changelog, modified the PNP ACPI scan handler code]
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    Reviewed-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    eec15edb
acpi_pnp.c 13.9 KB