Feature Request: Automated scan support for kernel-bypass devices (SPDK, vfio-pci) #392

Summary

smartctl_exporter cannot automatically discover and monitor NVMe devices accessed via kernel-bypass drivers such as SPDK (/dev/spdk/nvme*) and vfio-pci. These devices require an explicit -d nvme type flag to be passed to smartctl, but the current auto-scan (smartctl --scan) does not enumerate them since they are not exposed through the standard kernel block layer.

Current Behavior

smartctl --scan only discovers devices visible to the kernel (e.g. /dev/nvme*, /dev/sd*). Devices bound to vfio-pci or managed by SPDK are inaccessible through this path.

The --smartctl.device-include regexp flag also cannot help here — it filters devices found by scan, but SPDK/vfio-pci devices are never surfaced by scan in the first place.

The only current workaround is manually enumerating each device with --smartctl.device:

--smartctl.device=/dev/spdk/nvme0;nvme
--smartctl.device=/dev/spdk/nvme1;nvme

This is operationally painful on hosts with many drives, doesn't support rescan on hotplug.

Proposed Solution

Add a new repetable flag --smartctl.device-extra-scan or --smartctl.extra-device that accepts a regex pattern paired with an explicit device type:

--smartctl.extra-device='/dev/spdk;^nvme\d+$;nvme'
--smartctl.extra-device='/dev/vfio;^[0-9]+$;nvme'

Format: <directory>;<name-regex>;<device-type>

The exporter would match the devices with regex at startup and on each rescan interval, apply the existing --smartctl.device-include / --smartctl.device-exclude filters, and add matched devices with the specified type. This keeps the feature generic — any future kernel-bypass path works without further code changes.