Issue warning on unsupported CDI hook

To allow for CDI hooks to be added gradually we provide a generic no-op hook
for unrecognised subcommands. This will log a warning instead of erroring out.

An unsupported hook could be the result of a CDI specification referring to a
new hook that is not yet supported by an older NVIDIA Container Toolkit
version or a hook that has been removed in newer version.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

cmd/nvidia-cdi-hook/commands/commands.go

@@ -36,3 +36,16 @@ func New(logger logger.Interface) []*cli.Command {
 		cudacompat.NewCommand(logger),
 	}
 }
+
+// IssueUnsupportedHookWarning logs a warning that no hook or an unsupported
+// hook has been specified.
+// This happens if a subcommand is provided that does not match one of the
+// subcommands that has been explicitly specified.
+func IssueUnsupportedHookWarning(logger logger.Interface, c *cli.Context) {
+	args := c.Args().Slice()
+	if len(args) == 0 {
+		logger.Warningf("No CDI hook specified")
+	} else {
+		logger.Warningf("Unsupported CDI hook: %v", args[0])
+	}
+}