Device Configuration by ACPI

I just got a bug report for the Intel AC97 audio driver that i wrote a while ago. Bummer, but let's investigate what goes wrong.

Someone bought a shiny new Asus notebook, and noticed that he gets no sound. Installing the driver debug version thats available from BeBits, he created a debugging log file, which reveals these details:

MMBAR = 0
MBBAR = 0
INTR_LN = 0xff
INTR_PN = 0x02
IRQ not assigned to pin 2
ERROR: memory mapped IO not configured

You know what this means? The sound chipset resources are not configured, memory addresses are not assigned to the BARs (base address register), and the interrupt line is also not assigned (0xff or 0 means not assigned). The driver can't do these assignments, its the responsibility of computer BIOS and operating system. The driver can only do one thing: return B_ERROR and exit.

The important thing is: This is a notebook. Notebooks need to preserve power, and thus most notebook BIOS only enable the few devices that are needed for booting, like video card and harddisk controller. Most other devices are not touched, and not even configured. They need to be configured by the operating system.

Some BIOS have a setting like "PNP OS installed" which can be set to "no" or "disabled", indicating that a dumb OS is installed. Then all devices will be configured by the BIOS. This is available on many desktop motherboard, but almost never on notebooks.

On Notebooks, exclusivlely ACPI is used. ACPI means Advanced Configuration and Power Interface, and is available since spring 2001 in almost every desktop computer and notebook system. It's a specification that describes how the operating system can query which hardware is installed, and allows to configure them and assign resources. Some older systems can be configured by chipset specific PCI functions, but ACPI is better and doesn't depend on proprietary vendor specifications.

Unfortunately, BeOS and also Zeta is based on a design that is slightly older than 2001, and has neither PCI chipset specific, nor ACPI based device configuration implemented. If the motherboard doesn't have a "PNP OS installed" = "no" option, chances are that many devices like sound chipset, USB controller, network or TV cards won't work.

This is bad, very bad. Not only for the user, but also for us "your f***ing driver doesn't work here" driver writers.