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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 <rafael.j.wysocki@intel.com> Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com> |
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| .. | ||
| platform | ||
| acbuffer.h | ||
| acconfig.h | ||
| acexcep.h | ||
| acnames.h | ||
| acoutput.h | ||
| acpi_bus.h | ||
| acpi_drivers.h | ||
| acpi_io.h | ||
| acpi_lpat.h | ||
| acpi_numa.h | ||
| acpi.h | ||
| acpiosxf.h | ||
| acpixf.h | ||
| acrestyp.h | ||
| actbl1.h | ||
| actbl2.h | ||
| actbl3.h | ||
| actbl.h | ||
| actypes.h | ||
| acuuid.h | ||
| apei.h | ||
| button.h | ||
| ghes.h | ||
| hed.h | ||
| pdc_intel.h | ||
| processor.h | ||
| reboot.h | ||
| video.h | ||