Document PciBusID format

[neomantra]

While building my Nomad Device Plugin, I struggled to identify the exact format for DeviceLocality.PciBusID string.

I note that the Nomad docs show GUIDs like "PciBusID": "77cda534-0660-2688-6c2e-ad6c62fc5ff3". But I think that's because that's what the unit tests used?

I couldn't find how the NVidia plugin did it since I don't have any NVidia devices and the nvml API docs didn't say.

I want to make sure I present a value that is used appropriately by the Nomad Scheduler...

I ended up using values like this 0000:b1:00.0, as that's what comes back from lshw -businfo -class network:

	// "lshw -businfo -class network" sample output:
	// Bus info          Device     Class          Description
	// =======================================================
	// pci@0000:04:00.0  eth2       network        NetXtreme BCM5720 Gigabit Ethernet PCIe
	// pci@0000:04:00.1  eth3       network        NetXtreme BCM5720 Gigabit Ethernet PCIe
	// pci@0000:31:00.0             network        BCM57412 NetXtreme-E 10Gb RDMA Ethernet Controller
	// pci@0000:31:00.1             network        BCM57412 NetXtreme-E 10Gb RDMA Ethernet Controller
	// pci@0000:98:00.0  eth4       network        BCM57412 NetXtreme-E 10Gb RDMA Ethernet Controller
	// pci@0000:98:00.1  eth5       network        BCM57412 NetXtreme-E 10Gb RDMA Ethernet Controller
	// pci@0000:b1:00.0  eth0       network        SFC9220 10/40G Ethernet Controller
	// pci@0000:b1:00.1  eth1       network        SFC9220 10/40G Ethernet Controller

If there is an expected format, please document it.

Overall, it was pretty easy to make that plugin, thanks!

[tgross]

Hi @neomantra! I'm 99% certain that Nomad itself doesn't know or care about the format of that value. It's treated as an opaque identifier that gets passed through. But it'd be good if our docs at least match what folks will see if they query their devices.