Re: [PATCH] ACPI / driver core: Store a device pointer in struct acpi_dev_node

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Mon, Nov 11, 2013 at 02:45:39PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Subject: ACPI / driver core: Store an ACPI device pointer in struct acpi_dev_node
> 
> Modify struct acpi_dev_node to contain a pointer to struct acpi_device
> associated with the given device object (that is, its ACPI companion
> device) instead of an ACPI handle corresponding to it.  Introduce two
> new macros for manipulating that pointer in a CONFIG_ACPI-safe way,
> ACPI_COMPANION() and ACPI_COMPANION_SET(), and rework the
> ACPI_HANDLE() macro to take the above changes into account.
> Drop the ACPI_HANDLE_SET() macro entirely and rework its users to
> use ACPI_COMPANION_SET() instead.  For some of them who used to
> pass the result of acpi_get_child() directly to ACPI_HANDLE_SET()
> introduce a helper routine acpi_preset_companion() doing an
> equivalent thing.
> 
> The main motivation for doing this is that there are things
> represented by struct acpi_device objects that don't have valid
> ACPI handles (so called fixed ACPI hardware features, such as
> power and sleep buttons) and we would like to create platform
> device objects for them and "glue" them to their ACPI companions
> in the usual way (which currently is impossible due to the
> lack of valid ACPI handles).  However, there are more reasons
> why it may be useful.
> 
> First, struct acpi_device pointers allow of much better type checking
> than void pointers which are ACPI handles, so it should be more
> difficult to write buggy code using modified struct acpi_dev_node
> and the new macros.  Second, the change should help to reduce (over
> time) the number of places in which the result of ACPI_HANDLE() is
> passed to acpi_bus_get_device() in order to obtain a pointer to the
> struct acpi_device associated with the given "physical" device,
> because now that pointer is returned by ACPI_COMPANION() directly.
> Finally, the change should make it easier to write generic code that
> will build both for CONFIG_ACPI set and unset without adding explicit
> compiler directives to it.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

I tested this on Haswell as well and it works fine with ACPI enumerated
platform, I2C and SPI devices.

Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com> (on Haswell)
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>