The Linux Plug-and-Play HOWTO

9. Error Messages

9.1 Unexpected Interrupt

This means that an interrupt happened that no driver expected. It's unlikely that the hardware issued an interrupt by mistake. It's more likely that the software has a minor bug and doesn't realize that some software did something to cause the interrupt. In many cases you can safely ignore this error message, especially if it only happens once or twice at boot-time. For boot-time messages, look at the messages which are nearby for a clue as to what is going on. For example, if probing is going on, perhaps a probe for a physical device caused that device to issue an interrupt that the driver didn't expect. Perhaps the driver wasn't listening for the correct IRQ number.

9.2 Plug and Play Configuration Error (Dell BIOS)

The BIOS was unable to configure bus-resource. There may be an interrupt conflict which can't be avoided. Dell suggests that you remove some of your non-essential cards and see if it goes away. In one case this problem was due to a defective motherboard.

9.3 isapnp: Write Data Register 0xa79 already used (from logs)

If you use isa-pnp, the IO address 0xa79 must not ever be used by any device. So if other hardware is using 0xa79 when you try to load the isa-pnp module, you'll get this message in your logs and the isa-pnp will exit. One way to try to fix this is to load the isa-pnp module early before other hardware is initialized. For PCMCIA this means to load isa-pnp before running cb modules and service.

9.4 Can't allocate region (PCI)

Here "region" means address range. A PCI device that needs two addresses will have region 0 for the first address and region 1 for the second address needed. Use the command: lspci -vv to see the various resource regions (often just called regions) and whether the address is of type IO or memory. In PCI jargon region 2 is "base address 2" (or "base address register 2"), etc.