• Mika Westerberg's avatar
    ACPI / property: Allow holes in reference properties · b60e4ea4
    Mika Westerberg authored
    DT allows holes or empty phandles for references. This is used for example
    in SPI subsystem where some chip selects are native and others are regular
    GPIOs. In ACPI _DSD we currently do not support this but instead the
    preceding reference consumes all following integer arguments.
    
    For example we would like to support something like the below ASL fragment
    for SPI:
    
      Package () {
          "cs-gpios",
          Package () {
              ^GPIO, 19, 0, 0, // GPIO CS0
              0,               // Native CS
              ^GPIO, 20, 0, 0, // GPIO CS1
          }
      }
    
    The zero in the middle means "no entry" or NULL reference. To support this
    we change acpi_data_get_property_reference() to take firmware node and
    num_args as argument and rename it to __acpi_node_get_property_reference().
    The function returns -ENOENT if the given index resolves to "no entry"
    reference and -ENODATA when there are no more entries in the property.
    
    We then add static inline wrapper acpi_node_get_property_reference() that
    passes MAX_ACPI_REFERENCE_ARGS as num_args to support the existing
    behaviour which some drivers have been relying on.
    Signed-off-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    b60e4ea4
property.c 22.2 KB