Embedded Linux Development Using Yocto Project Cookbook - Second Edition

Defining buses and memory-addressable devices

Buses are typically defined by the compatible property or the simple-bus property (to define a memory-mapped bus with no specific driver binding), or both. The simple-bus property is needed so that child nodes to the bus are registered as platform devices.

For example, the soc node is defined as follows:

soc { 
    compatible = "simple-bus"; 
    #address-cells = <1>; 
    #size-cells = <1>; 
    ranges; 
 
    aips-bus@02000000 { /* AIPS1 */ 
        compatible = "fsl,aips-bus", "simple-bus"; 
        reg = <0x02000000 0x100000>; 
    } 
} 

The properties on the soc node are used to specify the memory addressability of the child nodes:

• address-cells: This property indicates how many base address cells are needed in the reg property.
• size-cells ...