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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.pdf
Signed-off-by: Rafael J. Wysocki <[email protected]>
Tested-by: Mika Westerberg <[email protected]>
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Introduce data structures and code allowing "built-in" properties
to be associated with devices in such a way that they will be used
by the device_property_* API if no proper firmware node (neither DT
nor ACPI) is present for the given device.
Each property is to be represented by a property_entry structure.
An array of property_entry structures (terminated with a null
entry) can be pointed to by the properties field of struct
property_set that can be added as a firmware node to a struct
device using device_add_property_set(). That will cause the
device_property_* API to use that property_set as the source
of properties if the given device does not have a DT node or
an ACPI companion device object associated with it.
Signed-off-by: Rafael J. Wysocki <[email protected]>
Tested-by: Heikki Krogerus <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
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Add a secondary pointer to struct fwnode_handle so as to make it
possible for a device to have two firmware nodes associated with
it at the same time, for example, an ACPI node and a node with
a set of properties provided by platform initialization code.
In the future that will allow device property lookup to fall back
from the primary firmware node to the secondary one if the given
property is not present there to make it easier to provide defaults
for device properties used by device drivers.
Introduce two helper routines, set_primary_fwnode() and
set_secondary_fwnode() allowing callers to add a primary/secondary
firmware node to the given device in such a way that
(1) If there's only one firmware node for that device, it will be
pointed to by the device's firmware node pointer.
(2) If both the primary and secondary firmware nodes are present,
the primary one will be pointed to by the device's firmware
node pointer, while the secondary one will be pointed to by the
primary node's secondary pointer.
(3) If one of these nodes is removed (by calling one of the new
nelpers with NULL as the second argument), the other one will
be preserved.
Make ACPI use set_primary_fwnode() for attaching its firmware nodes
to devices.
Signed-off-by: Rafael J. Wysocki <[email protected]>
Tested-by: Heikki Krogerus <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
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Now that we have struct fwnode_handle, we can use that to point to
ACPI companions from struct device objects instead of pointing to
struct acpi_device directly.
There are two benefits from that. First, the somewhat ugly and
hackish struct acpi_dev_node can be dropped and, second, the same
struct fwnode_handle pointer can be used in the future to point
to other (non-ACPI) firmware device node types.
Signed-off-by: Rafael J. Wysocki <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Acked-by: Grant Likely <[email protected]>
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