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diff --git a/Documentation/acpi/dsd/graph.txt b/Documentation/acpi/dsd/graph.txt new file mode 100644 index 000000000000..ac09e3138b79 --- /dev/null +++ b/Documentation/acpi/dsd/graph.txt @@ -0,0 +1,162 @@ +Graphs + + +_DSD +---- + +_DSD (Device Specific Data) [7] is a predefined ACPI device +configuration object that can be used to convey information on +hardware features which are not specifically covered by the ACPI +specification [1][6]. There are two _DSD extensions that are relevant +for graphs: property [4] and hierarchical data extensions [5]. The +property extension provides generic key-value pairs whereas the +hierarchical data extension supports nodes with references to other +nodes, forming a tree. The nodes in the tree may contain properties as +defined by the property extension. The two extensions together provide +a tree-like structure with zero or more properties (key-value pairs) +in each node of the tree. + +The data structure may be accessed at runtime by using the device_* +and fwnode_* functions defined in include/linux/fwnode.h . + +Fwnode represents a generic firmware node object. It is independent on +the firmware type. In ACPI, fwnodes are _DSD hierarchical data +extensions objects. A device's _DSD object is represented by an +fwnode. + +The data structure may be referenced to elsewhere in the ACPI tables +by using a hard reference to the device itself and an index to the +hierarchical data extension array on each depth. + + +Ports and endpoints +------------------- + +The port and endpoint concepts are very similar to those in Devicetree +[3]. A port represents an interface in a device, and an endpoint +represents a connection to that interface. + +All port nodes are located under the device's "_DSD" node in the +hierarchical data extension tree. The property extension related to +each port node must contain the key "port" and an integer value which +is the number of the port. The object it refers to should be called "PRTX", +where "X" is the number of the port. + +Further on, endpoints are located under the individual port nodes. The +first hierarchical data extension package list entry of the endpoint +nodes must begin with "endpoint" and must be followed by the number +of the endpoint. The object it refers to should be called "EPXY", where +"X" is the number of the port and "Y" is the number of the endpoint. + +Each port node contains a property extension key "port", the value of +which is the number of the port node. The each endpoint is similarly numbered +with a property extension key "endpoint". Port numbers must be unique within a +device and endpoint numbers must be unique within a port. + +The endpoint reference uses property extension with "remote-endpoint" property +name followed by a reference in the same package. Such references consist of the +the remote device reference, number of the port in the device and finally the +number of the endpoint in that port. Individual references thus appear as: + + Package() { device, port_number, endpoint_number } + +The references to endpoints must be always done both ways, to the +remote endpoint and back from the referred remote endpoint node. + +A simple example of this is show below: + + Scope (\_SB.PCI0.I2C2) + { + Device (CAM0) + { + Name (_DSD, Package () { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package () { + Package () { "compatible", Package () { "nokia,smia" } }, + }, + ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"), + Package () { + Package () { "port0", "PRT0" }, + } + }) + Name (PRT0, Package() { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package () { + Package () { "port", 0 }, + }, + ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"), + Package () { + Package () { "endpoint0", "EP00" }, + } + }) + Name (EP00, Package() { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package () { + Package () { "endpoint", 0 }, + Package () { "remote-endpoint", Package() { \_SB.PCI0.ISP, 4, 0 } }, + } + }) + } + } + + Scope (\_SB.PCI0) + { + Device (ISP) + { + Name (_DSD, Package () { + ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"), + Package () { + Package () { "port4", "PRT4" }, + } + }) + + Name (PRT4, Package() { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package () { + Package () { "port", 4 }, /* CSI-2 port number */ + }, + ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"), + Package () { + Package () { "endpoint0", "EP40" }, + } + }) + + Name (EP40, Package() { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package () { + Package () { "endpoint", 0 }, + Package () { "remote-endpoint", Package () { \_SB.PCI0.I2C2.CAM0, 0, 0 } }, + } + }) + } + } + +Here, the port 0 of the "CAM0" device is connected to the port 4 of +the "ISP" device and vice versa. + + +References +---------- + +[1] _DSD (Device Specific Data) Implementation Guide. + <URL:http://www.uefi.org/sites/default/files/resources/_DSD-implementation-guide-toplevel-1_1.htm>, + referenced 2016-10-03. + +[2] Devicetree. <URL:http://www.devicetree.org>, referenced 2016-10-03. + +[3] Documentation/devicetree/bindings/graph.txt + +[4] Device Properties UUID For _DSD. + <URL:http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf>, + referenced 2016-10-04. + +[5] Hierarchical Data Extension UUID For _DSD. + <URL:http://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.pdf>, + referenced 2016-10-04. + +[6] Advanced Configuration and Power Interface Specification. + <URL:http://www.uefi.org/sites/default/files/resources/ACPI_6_1.pdf>, + referenced 2016-10-04. + +[7] _DSD Device Properties Usage Rules. + Documentation/acpi/DSD-properties-rules.txt |