PCI Probing

Of the Enterprise 250 server's two PCI buses, Bus 0 (/pci@1f,4000 in the device tree) is unique in that it is the only PCI bus that contains motherboard (non plug-in) devices such as the on-board SCSI controller. By definition, such devices cannot be unplugged and swapped to change the order in which they are probed. To control the probing order of these devices, the system provides the NVRAM variable pci0-probe-list. This variable controls both the probing order and exclusion of devices on PCI Bus 0. The values that you can specify in the pci0-probe-list are defined in the following table.

Table 1-2 Probe Values

PCI Device Number	Function
2	PCI slot 2 (as labeled on system rear panel)
3	On-board SCSI controller for internal and external SCSI devices
4	PCI slot 1 (as labeled on system rear panel)
5	PCI slot 0 (as labeled on system rear panel)

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Note -

The values in this list are based on the PCI device number and do not refer to the back panel slot numbering scheme of 0-3.

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In the following example, the pci0-probe-list variable is used to define a probing order of 5-2-4, while excluding from the probe list the on-board SCSI controller for internal and external SCSI devices.

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ok setenv pci0-probe-list 5,2,4

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Note that the pci0-probe-list variable has no effect on probing of the top PCI slot (slot 3 on the system rear panel). However, another NVRAM variable, pci-slot-skip-list, is available for excluding any PCI slot from the PCI probe list. In the following example, the pci-slot-skip-list variable is used to exclude back panel slots 0 and 3 from the PCI probe list.

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ok setenv pci-slot-skip-list 0,3

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Note -

The values in the pci-slot-skip-list correspond to the back panel numbering scheme of 0-3. If a PCI slot number appears in this list, it will be excluded from probing even if it appears in the pci0-probe-list variable.

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