This document specifies the application of Open Firmware to the PowerPC Common Hardware Reference Platform (CHRP) ISA Parallel Port, including device-specific requirements and practices for initialization, properties, and methods. This device shall be a child of an ISA or EISA Bus Node.

2. Revision History

Revision 1.0 Unapproved DRAFT , Initial revision. Jordan Brown, Sunsoft and John Kingman, IBM editors

3. References

This Open Firmware System binding standard shall be used in conjunction with the following publications. When the following standards are superseded by an approved revision, the revision shall apply.

[1]: IEEE Std 1275-1994 Standard for Boot (Initialization, Configuration) Firmware, Core Practices and Requirements.
[2]: Core Errata, IEEE P1275.7/D4.
[3]: ISA/EISA/ISA-PnP binding to: IEEE Std 1275-1994, Standard for Boot (Initialization, Configuration) Firmware.
[4]: Device Support Extensions to: IEEE Std 1275-1994, Standard for Boot (Initialization, Configuration) Firmware.
[5]: PowerPC Microprocessor Common Hardware Reference Platform: I/O Device Reference. This document describes the PowerPC Common Hardware Reference Platform (CHRP) System Standard I/O Devices; hardware registers, register locations, and hardware attributes.
[6]: Open Firmware Recommended Practice: Interrupt Mapping.
[7]: Open Firmware Recommended Practice: Generic Names.
[8]: PowerPC Microprocessor Common Hardware Reference Platform binding to: IEEE Std 1275-1994, Standard for Boot (Initialization, Configuration) Firmware.

4. Definition of Terms

ECP: Extended Capabilities Port mode

EISA: Extended Industry Standard Architecture

EPP: Enhanced Parallel Port mode

ISA: Industry Standard Architecture

SPP: Standard Parallel Port mode

5. Device Characteristics (Informative)

The parallel port allows the attachment of devices that transfer 8 bits of parallel data at standard TTL levels. The primary function of the parallel port is to attach a printer with a parallel interface to the system. The parallel port supports ECP, EPP, and SPP modes.

6. Device-specific Configuration Variables

None.

7. Device Nodes

7.1. Properties

As specified in [1], [3] and [8], with the following additions or modifications.

7.1.1. Open Firmware-defined Properties for Device Nodes

"name" S

Standard property name, specifies the generic name of the device.

The meaning of this property is as defined in Open Firmware core document [1], as modified by the Generic Names Recommended Practice [7]. The value for nodes described by this specification shall be "parallel".

"device_type" S

Standard property name to define the device's implemented interface.

The meaning of this property is as defined in the Open Firmware core document [1]. The value for nodes described by this specification shall be "parallel".

"compatible" S

Standard property name, specifies device names with which this device is compatible.

The meaning of this property is as defined in Open Firmware, as modified by the Generic Names Recommended Practice [7]. As described in those documents, the entries are a list of device names with which this device is compatible, starting with the name of the device itself and progressing through successively less precise and possibly less functional compatible devices.

The value of this property shall include "chrp,ecp."

Additional entries may be supplied, at their appropriate position in the list, to describe devices with which this device is compatible.

"reg" S

Standard property name to define the package's registers.

The meaning of this property is as defined in the Interrupt Mapping Recommended Practice [6]. It describes the device's register set. The values which shall be assigned to this property are explained in the ISA/EISA/ISA-PnP binding[3] and the I/O Device Reference[5].

Note: In order to comply with the register requirements in [5] which require a bank of registers of length 8, the parallel port registers cannot be located at the legacy IBM-PC "LPT1" address (0x3bc).

"interrupts" S

Standard property name to define the package's interrupts.

The meaning of this property is as defined in the Interrupt Mapping Recommended Practice [6]. The values assigned to this property are explained in the ISA/EISA/ISA-PnP binding[3] and the I/O Device Reference[5].

"dma" S

Standard property name to define the package's DMA channels.

The values assigned to this property are explained in the ISA/EISA/ISA-PnP binding[3] and the I/O Device Reference[5]. This device shall have one DMA channel assigned to it for operation in ECP mode. The value of this property shall be the number of the DMA channel assigned to this device.

CHRP(TM) ISA Parallel Port Device Binding to IEEE 1275-1994 Standard for Boot (Initialization, Configuration) Firmware