Since fwnode may hold ERR_PTR(-ENODEV) or it may be NULL,
the fwnode type checks is_of_node(), is_acpi_node() and is
is_pset_node() need to consider it. Using IS_ERR_OR_NULL()
to check it.

Fixes: 0d67e0fa (device property: fix for a case of use-after-free)
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NHeikki Krogerus <heikki.krogerus@linux.intel.com>
[ rjw: Subject & changelog ]
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit 0824ab90e03c2e4239e890615f447e7962b1daa2

Was not using the correct macro. Updated a comment in
acoutput.h

Link: https://github.com/acpica/acpica/commit/0824ab90Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit 181f56605a771e0b91e24b0648d2565ca70bea20

This is used as a purely infomation message, without module name
and line number information. Therefore, these arguments are
not needed and they are unnecessary overhead.
Arguments are removed.
ACPICA BZ 872.

Link: https://github.com/acpica/acpica/commit/181f5660
Link: https://bugs.acpica.org/show_bug.cgi?id=872Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

acpi_processor_sleep is neither related nor used by CPUIdle framework.
It's used in system suspend/resume path as a syscore operation. It makes
more sense to move it to acpi/sleep.c where all the S-state transition
(a.k.a. Linux system suspend/hiberate) related code are present.

Also make it depend on CONFIG_ACPI_SYSTEM_POWER_STATES_SUPPORT so that
it's not compiled on architecture like ARM64 where S-states are not
yet defined in ACPI.
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPI 6.0 adds support for optional processor container device which may
contain child objects that are either processor devices or other processor
containers. This allows representing hierarchical processor topologies.

It is declared using the _HID of ACPI0010. It is an abstract container
used to represent CPU topology and should not be used to hotplug
purposes.

If no matching handler is found for a device in acpi_scan_attach_handler,
acpi_bus_attach does a default enumeration for those devices with valid
HID in the acpi namespace. This patch adds a scan handler for these ACPI
processor containers to avoid default that enumeration and ensures the
platform devices are not created for them.
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Remove a redundant function declaration in cppc_acpi.h for
mbox_send_message().  That function is defined in mailbox_client.h,
which is already included.
Signed-off-by: NTimur Tabi <timur@codeaurora.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Version 20160108
Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

All tool/utility signons.
Dual-license module header.
Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Document that acpi_video_handles_brightness_key_presses()'s return value
may change over time and should not be cached.
Signed-off-by: NHans de Goede <hdegoede@redhat.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Commit f06147f9 (ACPICA: Hardware: Enable firmware waking vector
for both 32-bit and 64-bit FACS) added three functions that aren't
present in upstream ACPICA, acpi_hw_set_firmware_waking_vectors(),
acpi_set_firmware_waking_vectors() and acpi_set_firmware_waking_vector64(),
to allow Linux to use the previously existing API for setting the
platform firmware waking vector.

However, that wasn't necessary, since the ACPI sleep support code
in Linux can be modified to use the upstream ACPICA's API easily
and the additional functions may be dropped which reduces the code
size and puts the kernel's ACPICA code more in line with the upstream.

Make the changes as per the above.  While at it, make the relevant
function desctiption comments reflect the upstream ACPICA's ones.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NLv Zheng <lv.zheng@intel.com>

ACPICA commit e81cedadd3a847d40f30bc9c52dfe441620ed12f

Version 20151218.

Link: https://github.com/acpica/acpica/commit/e81cedadSigned-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit 071eff738c59eda1792ac24b3b688b61691d7e7c

Execute any module-level code after each ACPI table (DSDT or SSDT)
is loaded into the namespace (rather than after all AML tables have
been loaded).  This matches the behavior of other ACPI
implementations and is required to support BIOS code that
depends on this behavior.

Link: https://github.com/acpica/acpica/commit/071eff73Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit dcaeaddfc11544f03e6323be4ac8ff8a1e014956

The intent for this exception is for low-level I/O operations,
especially Clib functions.

Link: https://github.com/acpica/acpica/commit/dcaeaddfSigned-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit 05492c4a7d1e106eb871a5e1357ed564d25740e5

1) Make the timer value output optional
2) Allow empty lines via null string or simple newline
3) No need for the object type name for strings and integers
4) Miscellaneous cleanup of output

Link: https://github.com/acpica/acpica/commit/05492c4aSigned-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit e4743959b59ad93eab7310adf756adc930be0ddb

This reverts commit 8e7a8753827660c3dd1f571f3185610402b756f0.

The _SUB method was found to be problematic for this interface
because some implementations use control methods. Therefore,
it is being removed.

Operations cannot be used because this interface is called
during the device discovery scan and the region handlers are
not fully installed at that time.

Link: https://github.com/acpica/acpica/commit/e4743959Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The patch reduces source code differences between the Linux kernel and the
ACPICA upstream so that the linuxized ACPICA 20151218 release can be
applied with reduced human intervention.

The pscode.c has already been out of sync for months, and it becomes more
and more difficult to merge pscode.c changes, so instead of update the
affected lines of pscode.c, this patch synchronizes entire pscode.c file.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Several drivers want to know if the acpi-video is generating key-presses
for brightness change hotkeys to avoid sending double key-events to
userspace for these. Currently these driver use this construct for this:

	if (acpi_video_get_backlight_type() == acpi_backlight_vendor)
		report_brightness_key_event();

This indirect way of detecting if acpi-video is active does not make the
code easier to understand, and in some cases it is wrong because just
because the preferred type != vendor does not mean that acpi-video is
actually listening for brightness events, e.g. there may be no acpi-video
bus on the system at all.

This commit adds a acpi_video_handles_brightness_key_presses() helper
function, making the code needing this functionality both easier to read
and more correct.
Signed-off-by: NHans de Goede <hdegoede@redhat.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch adds /sys/kernel/debug/acpi/acpidbg, which can be used by
userspace programs to access ACPICA debugger functionalities.

Known issue:
1. IO flush support
   acpi_os_notify_command_complete() and acpi_os_wait_command_ready() can
   be used by acpi_dbg module to implement .flush() filesystem operation.
   While this patch doesn't go that far. It then becomes userspace tool's
   duty now to flush old commands before executing new batch mode commands.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit 11522d6b894054fc4d62dd4f9863ec151296b386

The ACPI_DEBUGGER_EXEC is a problem now when the debugger code is compiled
but runtime disabled. They actually will get executed in this situation.
Although such executions are harmless if we can correctly make
acpi_db_single_step() a runtime stub, users may still do not want to see the
debugger print messages logged into OSPMs' kernel logs when a debugger
driver is not loaded to enable the debugger during runtime.

This patch fixes this issue by introducing new stub mechanism instead of
ACPI_DEBUGGER_EXEC. Lv Zheng.

Link: https://github.com/acpica/acpica/commit/11522d6bSigned-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The following mechanisms are OSPM specific:
1. Redirect output destination to console: no file redirection will be
   needed by an in-kernel debugger, there is even no file can be accessed
   when the debugger is running in the kernel mode.
2. Output command prompts: programs other than acpiexec can have different
   prompt characters and the prompt characters may be implemented as a
   special character sequence to form a char device IO protocol.
3. Command ready/complete handshake: OSPM debugger may wait more conditions
   to implement OSPM specific semantics (for example, FIFO full/empty
   conditions for O_NONBLOCK or IO open/close conditions).
Leaving such OSPM specific stuffs in the ACPICA debugger core blocks
Linux debugger IO driver implementation.

Several new OSL APIs are provided by this patch:
1. acpi_os_initialize_command_signals: initialize command handshake mechanism
   or any other OSPM specific stuffs.
2. acpi_os_terminate_command_signals: reversal of
   acpi_os_initialize_command_signals.
3. acpi_os_wait_command_ready: putting debugger task into wait state when a
   command is not ready. OSPMs can terminate command loop by returning
   AE_CTRL_TERMINATE from this API. Normally, wait_event() or
   wait_for_multiple_object() may be used to implement this API.
4. acpi_os_notify_command_complete: putting user task into running state when a
   command has been completed. OSPMs can terminate command loop by
   returning AE_CTRL_TERMINATE from this API. Normally, wake_up() or
   set_event() may be used to implement this API.
This patch also converts current command signaling implementation into a
generic debugger layer (osgendbg.c) to be used by the existing OSPMs or
acpiexec, in return, Linux can have chance to implement its own command
handshake mechanism. This patch also implements acpiexec batch mode in a
multi-threading mode comaptible style as a demo (this can be confirmed by
configuring acpiexec into DEBUGGER_MULTI_THREADED mode where the batch mode
is still working). Lv Zheng.

Note that the OSPM specific command handshake mechanism is required by
Linux kernel because:
1. Linux kernel trends to use wait queue to synchronize two threads, using
   mutexes to achieve that will cause false "dead lock" warnings.
2. The command handshake mechanism implemented by ACPICA is implemented in
   this way because of a design issue in debugger IO streaming. Debugger IO
   outputs are simply cached using a giant buffer, this should be tuned by
   Linux in the future.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

D3cold is only regarded as valid if the "_PR3" object is
present for the given device after the commit 20dacb71
("ACPI/PM: Rework device power management to follow ACPI 6").

But some old BIOS only defined "_PS3" for the D3COLD device,
such as ZPODD device. And old kernel also believes the device with
"_PS3" is a D3COLD device.

So, add some logics for supporting D3 COLD device with old BIOS
which is compatible with earlier ACPI spec and kernel behavior.

Link: http://marc.info/?l=linux-acpi&m=144946938709759&w=2Signed-off-by: NKen Xue <Ken.Xue@amd.com>
Reported-and-tested-by: NGang Long <Gang.Long@amd.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

There's an idiom in use by 7 Linux drivers to detect the presence of a
particular ACPI HID by walking the namespace with acpi_get_devices().
The callback passed to acpi_get_devices() is mostly identical across
the drivers, leading to lots of duplicate code.

Add acpi_dev_present(), the ACPI equivalent to pci_dev_present(),
allowing us to deduplicate all that boilerplate in the drivers.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Reviewed-by: NHanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

These DMA APIs are replaced with the newer versions, which return
the enum dev_dma_attr. So, we can safely remove them.
Signed-off-by: NSuravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Acked-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NHanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Adding acpi_get_dma_attr() to query DMA attributes of ACPI devices.
It returns the enum dev_dma_attr, which communicates DMA information
more clearly. This API replaces the acpi_check_dma(), which will be
removed in subsequent patch.

This patch also provides a convenient function, acpi_dma_supported(),
to check DMA support of the specified ACPI device.
Signed-off-by: NSuravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Acked-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NHanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPI configurations can now mark devices as noncoherent,
support that choice.

NOTE: This is required to support USB on ARM Juno Development Board.
Signed-off-by: NJeremy Linton <jeremy.linton@arm.com>
Signed-off-by: NSuravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Acked-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NHanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit e9c75ca267262326e80d49a290e8387a5963e2d2

Version 20150930.

Link: https://github.com/acpica/acpica/commit/e9c75ca2Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch enables ACPICA debugger files using a configurable
CONFIG_ACPI_DEBUGGER configuration item. Those debugger related code that
was originally masked as ACPI_FUTURE_USAGE now gets unmasked.

Necessary OSL stubs are also added in this patch:
1. acpi_os_readable(): This should be arch specific in Linux, while this
    patch doesn't introduce real implementation and a complex mechanism to
    allow architecture specific acpi_os_readable() to be implemented to
    validate the address. It may be done by future commits.
2. acpi_os_get_line(): This is used to obtain debugger command input. This
    patch only introduces a simple KDB concept example in it and the
    example should be co-working with the code implemented in
    acpi_os_printf(). Since this KDB example won't be compiled unless
    ENABLE_DEBUGGER is defined and it seems Linux has already stopped to
    use ENABLE_DEBUGGER, thus do not expect it can work properly.

This patch also cleans up all other ACPI_FUTURE_USAGE surroundings
accordingly.
1. Since linkage error can be automatically detected, declaration in the
   headers needn't be surrounded by ACPI_FUTURE_USAGE.
   So only the following separate exported fuction bodies are masked by
   this macro (other exported fucntions may have already been masked at
   entire module level via drivers/acpi/acpica/Makefile):
     acpi_install_exception_handler()
     acpi_subsystem_status()
     acpi_get_system_info()
     acpi_get_statistics()
     acpi_install_initialization_handler()
2. Since strip can automatically zap the no-user functions, functions that
   are not marked with ACPI_EXPORT_SYMBOL() needn't get surrounded by
   ACPI_FUTURE_USAGE.
   So the following function which is not used by Linux kernel now won't
   get surrounded by this macro:
     acpi_ps_get_name()
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA: Debugger: Add thread ID support so that single step mode can only apply to the debugger thread

When the debugger is running in the kernel mode, acpi_db_single_step() may
also be invoked by the kernel runtime code path but the single stepping
command prompt may be erronously logged as the kernel logs and runtime code
path cannot proceed.

This patch fixes this issue by adding acpi_gbl_db_thread_id for the debugger
thread and preventing acpi_db_single_step() to be invoked from other threads.

It is not suitable to add acpi_thread_id parameter for acpi_os_execute() as
the function may be implemented as work queue on some hosts. So it is
better to let the hosts invoke acpi_set_debugger_thread_id(). Currently
acpiexec is not configured as DEBUGGER_MULTI_THREADED, but we can do this.
When we do this, it is better to invoke acpi_set_debugger_thread_id() in
acpi_os_execute() when the execution type is OSL_DEBUGGER_MAIN_THREAD. The
support should look like:
  create_thread(&tid);
  if (type == OSL_DEBUGGER_MAIN_THREAD)
      acpi_set_debugger_thread_id(tid);
  resume_thread(tid);
Similarly, semop() may be used for pthread implementation. But this patch
simply skips debugger thread ID check for application instead of
introducing such complications as there is no need to skip
acpi_db_single_step() for an application debugger - acpiexec.

Note that the debugger thread ID can also be used by acpi_os_printf() to
filter out debugger output. Lv Zheng.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit 8d0f96e2a11a4ceabb2cae4b41e0ce1f4d3786b9

Adds much stricter typechecking in the iASL compiler, and
also adds some additional checking in the interpreter.

Link: https://github.com/acpica/acpica/commit/8d0f96e2Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit 534deab97fb416a13bfede15c538e2c9eac9384a

Updated one of the memory subtable flags to clarify.

Link: https://github.com/acpica/acpica/commit/534deab9Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit 6b2701f619040e803313363f516b200e362a9100

Make these mutex objects independent of the deadlock detection mechanism.
This mechanism caused failures with the multithread debugger.

This patch doesn't affect Linux kernel as debugger is currently not fully
functioning in the Linux kernel. And the further debugger cleanups will
take care of handling debugger command signalling correctly instead of
using such kind of mutexes. So it is safe to leave this patch as it is.

Link: https://github.com/acpica/acpica/commit/6b2701f6Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

ACPICA commit eea1f0e561893b6d6417913b2d224082fe3a0a5e

Remove use of ACPI_DEBUGGER and ACPI_DISASSEMBLER where these
defines are used around entire modules.

Note: This type of code also causes problems with IDEs.

Link: https://github.com/acpica/acpica/commit/eea1f0e5Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

For each detected ACPI Processor object (ACPI0007), search its
device handle for CPPC specific tables (i.e. _CPC) and extract
CPU specific performance capabilities.
Signed-off-by: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Reviewed-by: NAl Stone <al.stone@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

CPPC stands for Collaborative Processor Performance Controls
and is defined in the ACPI v5.0+ spec. It describes CPU
performance controls on an abstract and continuous scale
allowing the platform (e.g. remote power processor) to flexibly
optimize CPU performance with its knowledge of power budgets
and other architecture specific knowledge.

This patch adds a shim which exports commonly used functions
to get and set CPPC specific controls for each CPU. This enables
CPUFreq drivers to gather per CPU performance data and use
with exisiting governors or even allows for customized governors
which are implemented inside CPUFreq drivers.
Signed-off-by: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Reviewed-by: NAl Stone <al.stone@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This commit removes all CONFIG_.*{,_MODULE} in ACPI code, replacing it
with IS_ENABLED().
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This is preparation for using kstrdup_const to initialize that member.
Signed-off-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

One wouldn't expect a "match" function modify the string it searches
for, and indeed the only instance of the struct
acpi_scan_handler::match callback, acpi_pnp_match, can easily be
changed. While there, update its helper matching_id().

This is also preparation for constifying struct acpi_hardware_id::id.
Signed-off-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Modify is_acpi_node() to return "true" for ACPI data-only subnodes as
well as for ACPI device objects and change the name of to_acpi_node()
to to_acpi_device_node() so it is clear that it covers ACPI device
objects only.  Accordingly, introduce to_acpi_data_node() to cover
data-only subnodes in an analogous way.

With that, make the fwnode_property_* family of functions work with
ACPI data-only subnodes introduced previously.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: NMika Westerberg <mika.westerberg@linux.intel.com>

Add infrastructure needed to expose data-only subnodes of ACPI
device objects introduced previously via sysfs.

Each data-only subnode is represented as a sysfs directory under
the directory corresponding to its parent object (a device or a
data-only subnode).  Each of them has a "path" attribute (containing
the full ACPI namespace path to the object the subnode data come from)
at this time.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: NMika Westerberg <mika.westerberg@linux.intel.com>

In some cases, the information expressed via device properties is
hierarchical by nature.  For example, the properties of a composite
device consisting of multiple semi-dependent components may need
to be represented in the form of a tree of property data sets
corresponding to specific components of the device.

Unfortunately, using ACPI device objects for this purpose turns out
to be problematic, mostly due to the assumption made by some operating
systems (that platform firmware generally needs to work with) that
each device object in the ACPI namespace represents a device requiring
a separate driver.  That assumption leads to complications which
reportedly are impractically difficult to overcome and a different
approach is needed for the sake of interoperability.

The approach implemented here is based on extending _DSD via pointers
(links) to additional ACPI objects returning data packages formatted
in accordance with the _DSD formatting rules defined by Section 6.2.5
of ACPI 6.  Those additional objects are referred to as data-only
subnodes of the device object containing the _DSD pointing to them.

The links to them need to be located in a separate section of the
_DSD data package following UUID dbb8e3e6-5886-4ba6-8795-1319f52a966b
referred to as the Hierarchical Data Extension UUID as defined in [1].
Each of them is represented by a package of two strings.  The first
string in that package (the key) is regarded as the name of the
data-only subnode pointed to by the link.  The second string in it
(the target) is expected to hold the ACPI namespace path (possibly
utilizing the usual ACPI namespace search rules) of an ACPI object
evaluating to a data package extending the _DSD.

The device properties initialization code follows those links,
creates a struct acpi_data_node object for each of them to store
the data returned by the ACPI object pointed to by it and processes
those data recursively (which may lead to the creation of more
struct acpi_data_node objects if the returned data package contains
the Hierarchical Data Extension UUID section with more links in it).

All of the struct acpi_data_node objects are present until the the
ACPI device object containing the _DSD with links to them is deleted
and they are deleted along with that object.

[1]: http://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.pdfSigned-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: NMika Westerberg <mika.westerberg@linux.intel.com>