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device_tree_standard_properties

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device_tree_standard_properties [2018/11/18 12:55]
rpjday [virtual-reg]
device_tree_standard_properties [2018/11/18 13:54]
rpjday [ranges]
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 ==== ranges ==== ==== 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 ==== ==== dma-ranges ====
device_tree_standard_properties.txt · Last modified: 2018/11/18 13:54 by rpjday