Initialising control data for a device

An apparatus comprising:

• a non-CPU device comprising at least one of a memory management unit, a direct memory access controller, a USB controller or a peripheral controller;
• local storage circuitry configured to store data within said non-CPU device;
• one or more capability identification registers in the local storage circuitry configured to store an identification value having one of a first value and a second value, wherein a CPU separated from the non-CPU device by a bus or interconnect is permitted to inspect said one or more capability identification registers of the non-CPU device;
• and
• control circuitry configured to determine, on initialization of the non-CPU device, whether the identification value has the first value or the second value, said identification value being visible to the software executing on said CPU separated from the non-CPU device by said bus or interconnect, and said identification value indicating whether control data is to be stored in a memory accessible to the non-CPU device via said bus or interconnect or in the local storage circuitry provided within the non-CPU device, wherein the non-CPU device is configured to use the control data for controlling said operations, the memory and the local storage circuitry are separated by said bus or interconnect, and the memory is also accessible to the CPU via said bus or interconnect;
• wherein when the identification value visible to the software executing on said CPU separated from the non-CPU device by said bus or interconnect has the first value, the control circuitry is configured, on initialization of the non-CPU device, to allocate space in said memory accessible to the non-CPU device via the bus or interconnect for storing the control data and to write an address of the allocated space in said memory to a control data pointer storage location of the non-CPU device;
• and
• when the identification value visible to the software executing on said CPU separated from the non-CPU device by said bus or interconnect has the second value, the control circuitry is configured, on initialization of the non-CPU device, to omit allocating the space in said memory accessible to the non-CPU device via the bus or interconnect for storing the control data, and the control data pointer storage location specifies a preset address indicative of a location for storing the control data in the local storage circuitry within said non-CPU device, and the control data is not stored in said memory accessible to the non-CPU device via the bus or interconnect.

An apparatus comprising:

• a non-CPU device comprising at least one of a memory management unit, a direct memory access controller, a USB controller or a peripheral controller;
• means for locally storing data within said non-CPU device;
• means for storing an identification value having one of a first value and a second value, wherein a CPU separated from the non-CPU device by a bus or interconnect is permitted to inspect said means for storing an identification value;
• and
• control means for determining, on initialization of the non-CPU device, whether the identification value has the first value or the second value, said identification value being visible to the software executing on said CPU separated from the non-CPU device by said bus or interconnect, and said identification value indicating whether control data is to be stored in a memory accessible to the non-CPU device via said bus or interconnect or in the means for locally storing data provided within the non-CPU device, wherein the non-CPU device is configured to use the control data for controlling said operations, the memory and the means for locally storing data are separated by said bus or interconnect, and the memory is also accessible to the CPU via said bus or interconnect;
• wherein when the identification value visible to the software executing on said CPU separated from the non-CPU device by said bus or interconnect has the first value, the control means is configured, on initialization of the non-CPU device, to allocate space in said memory accessible to the non-CPU device via the bus or interconnect, for storing the control data and write an address of the allocated space in said memory to a control data pointer storage location of the non-CPU device;
• and
• when the identification value visible to the software executing on said CPU separated from the non-CPU device by said bus or interconnect has the second value, the control means is configured, on initialization of the non-CPU device, to omit allocating the space in said memory accessible to the non-CPU device via the bus or interconnect for storing the control data, and the control data pointer storage location specifies a preset address indicative of a location for locally storing the control data in said means for locally storing data within said non-CPU device, and the control data is not stored in said memory accessible to the non-CPU device via the bus or interconnect.