Extend the FeatureSource interface with new methods for configuration
handling. This enables easier on-the fly reconfiguration of the
feature sources. Further, it simplifies adding config support to feature
sources in the future. Stub methods are added to sources that do not
currently have any configurability.
The patch fixes some (corner) cases with the overrides (--options)
handling, too:
- Overrides were not applied if config file was missing or its parsing
failed
- Overrides for a certain source did not have effect if an empty config
for the source was specified in the config file. This was caused by
the first pass of parsing (config file) setting a nil pointer to the
source-specific config, effectively detaching it from the main config.
The second pass would then create a new instance of the source
specific config, but, this was not visible in the feature source, of
course.
This builds on the PCI support to enable the discovery of USB devices.
This is primarily intended to be used for the discovery of Edge-based
heterogeneous accelerators that are connected via USB, such as the Coral
USB Accelerator and the Intel NCS2 - our main motivation for adding this
capability to NFD, and as part of our work in the SODALITE H2020
project.
USB devices may define their base class at either the device or
interface levels. In the case where no device class is set, the
per-device interfaces are enumerated instead. USB devices may
furthermore have multiple interfaces, which may or may not use the
identical class across each interface. We therefore report device
existence for each unique class definition to enable more fine-grained
labelling and node selection.
The default labelling format includes the class, vendor and device
(product) IDs, as follows:
feature.node.kubernetes.io/usb-fe_1a6e_089a.present=true
As with PCI, a subset of device classes are whitelisted for matching.
By default, there are only a subset of device classes under which
accelerators tend to be mapped, which is used as the basis for
the whitelist. These are:
- Video
- Miscellaneous
- Application Specific
- Vendor Specific
For those interested in matching other classes, this may be extended
by using the UsbId rule provided through the custom source. A full
list of class codes is provided by the USB-IF at:
https://www.usb.org/defined-class-codes
For the moment, owing to a lack of a demonstrable use case, neither
the subclass nor the protocol information are exposed. If this
becomes necessary, support for these attributes can be trivially
added.
Signed-off-by: Paul Mundt <paul.mundt@adaptant.io>
