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device_tree_standard_properties

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device_tree_standard_properties [2018/11/18 12:52]
rpjday [#address-cells, #size-calls]
device_tree_standard_properties [2018/11/18 13:54] (current)
rpjday [ranges]
Line 27: Line 27:
 The value is a <​prop-encoded-array>,​ composed of an arbitrary number of pairs of address and length, <address length>. The number of <u32> cells required to specify the address and length are bus-specific and are specified by the #​address-cells and #size-cells properties in the parent of the device node. If the parent node specifies a value of 0 for #​size-cells,​ the length field in the value of reg shall be omitted. The value is a <​prop-encoded-array>,​ composed of an arbitrary number of pairs of address and length, <address length>. The number of <u32> cells required to specify the address and length are bus-specific and are specified by the #​address-cells and #size-cells properties in the parent of the device node. If the parent node specifies a value of 0 for #​size-cells,​ the length field in the value of reg shall be omitted.
  
 +==== virtual-reg ====
 +
 +Seems to be PowerPC only.
 +
 +==== ranges ====
 +
 +The format of the value of the ranges property is an arbitrary number of triplets of (child-bus-address,​ parent-bus-address,​ length)
 +
 +  * The child-bus-address is a physical address within the child bus’ address space. The number of cells to represent the address is bus dependent and can be determined from the #​address-cells of this node (the node in which the ranges property appears).
 +  * The parent-bus-address is a physical address within the parent bus’ address space. The number of cells to represent the parent address is bus dependent and can be determined from the #​address-cells property of the node that defines the parent’s address space.
 +  * The length specifies the size of the range in the child’s address space. The number of cells to represent the size can be determined from the #size-cells of this node (the node in which the ranges property appears).
 +
 +If the property is defined with an <​empty>​ value, it specifies that the parent and child address space is identical, and no address translation is required.
 +
 +If the property is not present in a bus node, it is assumed that no mapping exists between children of the node and the parent address space.
 +==== dma-ranges ====
device_tree_standard_properties.1542545529.txt.gz · Last modified: 2018/11/18 12:52 by rpjday