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Standard Properties

Some standard Name Registry properties names are specified for device entries. These names should not be used for other purposes. Standard reserved property names used by PCI expansion cards are listed in Table 10-1. Property names beginning with APPL are reserved for Apple use.

Normally, the device tree shows several properties attached to each device. Most of these properties are created and used by Open Firmware and are described fully in IEEE Standard 1275. Some properties are Apple specific and are required only by Power Macintosh computers or Mac OS. Following are some notes on the properties listed in Table 10-1 :

• Manufacturers of PCI cards should use their United States stock symbol (if they are a publicly traded company) as the hardware manufacturer's ID in the name property. Otherwise, they can ask the IEEE to assign a 24-bit ID number by contacting

Registration Authority Committee IEEE, Inc. 445 Hoes Lane Piscataway, NJ 08855-1331 Telephone 809-562-3812

• Mac OS native drivers should use the following value for their driver property:

driver,AAPL,MacOS,PowerPC

• A standard property that is important to native drivers is the assigned-addresses property defined in PCI Bus Binding to IEEE 1275-1994. The assigned-addresses property tells the driver where a card's relocatable address locations have been placed in physical memory. With all routines except the Expansion Bus Manager I/O functions, driver code must resolve assigned-addresses values to AAPL,address values before using them. Sample code that retrieves an assigned-addresses property from the Name Registry is shown in Listing 9-3.
• Drivers can use the vendor-id, device-id, class-code, and revision-id properties to distinguish one card from another. However, these values typically refer to the controller on the card rather than the card itself. For example, software will be unable to use these properties to distinguish between two video cards that use the same controller chip. Driver writers can make the cards distinct by giving different names to them in their FCode assignments.
• The fcode-rom-offset property contains the location in the PCI card's expansion ROM at which the FCode that produces the node is found. The FCode tokenizer tool can use the value of this property to determine the values of other properties, such as driver. If a card's expansion ROM contains no FCode, the fcode-rom-offset property will be absent from the card's Name Registry entry.
• The driver-ref pointer can be important. This property is created by the system when a device driver is installed; it is the driver reference as defined by Inside Macintosh: Devices. The property is removed when the driver is removed. The presence of this property can be used to determine whether a particular device is open.
• The driver-descriptor property is a structure taken from the driver header; it defines various characteristics of the device. The contents of this property are defined in Driver Description Structure.
• The AAPL,address property is a vector to an array of logical address pointers, as described in Fast I/O Space Cycle Generation.
• The AAPL,interrupts property is an internal interrupt number that the Open Firmware startup process creates before any FCode is read from the card. This property is implementation dependent and does not necessarily reflect the actual interrupt bit number in the interrupt controller.
• The AAPL, slot-name property is an identifier for the hardware slot in which the card is plugged. This property is created by the Open Firmware startup process before any FCode is read from the card. Its value may be different with different Power Macintosh models.
• The height, width, linebytes, and depth properties are attached to the Name Registry entries of graphic display devices to define each display's characteristics.
• The property driver, xxx , yyy, zzz provides access to driver code. An expansion card ROM may contain a number of different drivers suited to different operating systems and machine architectures. The value of xxx specifies the manufacturer of the hardware (AAPL for Apple Computer, Inc.), yyy specifies the operating system ( MacOS), and zzz specifies the instruction set architecture ( PowerPC). The value of driver, xxx, yyy, zzz is the driver code itself, which can be quite large; there is no defined upper limit to the size of a property's data. Although a PCI card may define a number of drivers, only drivers appropriate to an available operating system will be placed in the device tree, and therefore only these drivers can be accessed through the Name Registry.