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authorMika Westerberg <mika.westerberg@linux.intel.com>2014-10-21 15:33:55 +0400
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-11-04 23:58:21 +0300
commitffdcd955c3078af3ce117edcfce80fde1a512bed (patch)
tree93a3be25da68fb204bece7bc32fac29629963437 /include/linux/acpi.h
parenta5501fe4eaa4ee35f8de6efac8d1c4ad16094951 (diff)
downloadlinux-ffdcd955c3078af3ce117edcfce80fde1a512bed.tar.xz
ACPI: Add support for device specific properties
Device Tree is used in many embedded systems to describe the system configuration to the OS. It supports attaching properties or name-value pairs to the devices it describe. With these properties one can pass additional information to the drivers that would not be available otherwise. ACPI is another configuration mechanism (among other things) typically seen, but not limited to, x86 machines. ACPI allows passing arbitrary data from methods but there has not been mechanism equivalent to Device Tree until the introduction of _DSD in the recent publication of the ACPI 5.1 specification. In order to facilitate ACPI usage in systems where Device Tree is typically used, it would be beneficial to standardize a way to retrieve Device Tree style properties from ACPI devices, which is what we do in this patch. If a given device described in ACPI namespace wants to export properties it must implement _DSD method (Device Specific Data, introduced with ACPI 5.1) that returns the properties in a package of packages. For example: Name (_DSD, Package () { ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), Package () { Package () {"name1", <VALUE1>}, Package () {"name2", <VALUE2>}, ... } }) The UUID reserved for properties is daffd814-6eba-4d8c-8a91-bc9bbf4aa301 and is documented in the ACPI 5.1 companion document called "_DSD Implementation Guide" [1], [2]. We add several helper functions that can be used to extract these properties and convert them to different Linux data types. The ultimate goal is that we only have one device property API that retrieves the requested properties from Device Tree or from ACPI transparent to the caller. [1] http://www.uefi.org/sites/default/files/resources/_DSD-implementation-guide-toplevel.htm [2] http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Reviewed-by: Grant Likely <grant.likely@linaro.org> Signed-off-by: Darren Hart <dvhart@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'include/linux/acpi.h')
-rw-r--r--include/linux/acpi.h40
1 files changed, 40 insertions, 0 deletions
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 407a12f663eb..dcdf8738898c 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -659,4 +659,44 @@ do { \
#endif
#endif
+/* Device properties */
+
+#define MAX_ACPI_REFERENCE_ARGS 8
+struct acpi_reference_args {
+ struct acpi_device *adev;
+ size_t nargs;
+ u64 args[MAX_ACPI_REFERENCE_ARGS];
+};
+
+#ifdef CONFIG_ACPI
+int acpi_dev_get_property(struct acpi_device *adev, const char *name,
+ acpi_object_type type, const union acpi_object **obj);
+int acpi_dev_get_property_array(struct acpi_device *adev, const char *name,
+ acpi_object_type type,
+ const union acpi_object **obj);
+int acpi_dev_get_property_reference(struct acpi_device *adev, const char *name,
+ const char *cells_name, size_t index,
+ struct acpi_reference_args *args);
+#else
+static inline int acpi_dev_get_property(struct acpi_device *adev,
+ const char *name, acpi_object_type type,
+ const union acpi_object **obj)
+{
+ return -ENXIO;
+}
+static inline int acpi_dev_get_property_array(struct acpi_device *adev,
+ const char *name,
+ acpi_object_type type,
+ const union acpi_object **obj)
+{
+ return -ENXIO;
+}
+static inline int acpi_dev_get_property_reference(struct acpi_device *adev,
+ const char *name, const char *cells_name,
+ size_t index, struct acpi_reference_args *args)
+{
+ return -ENXIO;
+}
+#endif
+
#endif /*_LINUX_ACPI_H*/