Add imex mode to CDI spec generation

This change adds a imex mode to CDI spec generation. This mode detected
generates CDI specifications for existing IMEX channels. By default these
devices have the fully qualified CDI device names:

nvidia.com/imex-channel=<ID>

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

pkg/nvcdi/lib-imex.go

@@ -0,0 +1,118 @@
+/**
+# Copyright 2024 NVIDIA CORPORATION
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package nvcdi
+
+import (
+	"fmt"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"tags.cncf.io/container-device-interface/pkg/cdi"
+	"tags.cncf.io/container-device-interface/specs-go"
+
+	"github.com/NVIDIA/go-nvlib/pkg/nvlib/device"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/discover"
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/edits"
+	"github.com/NVIDIA/nvidia-container-toolkit/pkg/nvcdi/spec"
+)
+
+type imexlib nvcdilib
+
+var _ Interface = (*imexlib)(nil)
+
+const (
+	classImexChannel = "imex-channel"
+)
+
+// GetSpec should not be called for imexlib.
+func (l *imexlib) GetSpec() (spec.Interface, error) {
+	return nil, fmt.Errorf("unexpected call to imexlib.GetSpec()")
+}
+
+// GetAllDeviceSpecs returns the device specs for all available devices.
+func (l *imexlib) GetAllDeviceSpecs() ([]specs.Device, error) {
+	channelsDiscoverer := discover.NewCharDeviceDiscoverer(
+		l.logger,
+		l.devRoot,
+		[]string{"/dev/nvidia-caps-imex-channels/channel*"},
+	)
+
+	channels, err := channelsDiscoverer.Devices()
+	if err != nil {
+		return nil, err
+	}
+
+	var channelIDs []string
+	for _, channel := range channels {
+		channelIDs = append(channelIDs, filepath.Base(channel.Path))
+	}
+
+	return l.GetDeviceSpecsByID(channelIDs...)
+}
+
+// GetCommonEdits returns an empty set of edits for IMEX devices.
+func (l *imexlib) GetCommonEdits() (*cdi.ContainerEdits, error) {
+	return edits.FromDiscoverer(discover.None{})
+}
+
+// GetDeviceSpecsByID returns the CDI device specs for the IMEX channels specified.
+func (l *imexlib) GetDeviceSpecsByID(ids ...string) ([]specs.Device, error) {
+	var deviceSpecs []specs.Device
+	for _, id := range ids {
+		trimmed := strings.TrimPrefix(id, "channel")
+		_, err := strconv.ParseUint(trimmed, 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("invalid channel ID %v: %w", id, err)
+		}
+		path := "/dev/nvidia-caps-imex-channels/channel" + trimmed
+		deviceSpec := specs.Device{
+			Name: trimmed,
+			ContainerEdits: specs.ContainerEdits{
+				DeviceNodes: []*specs.DeviceNode{
+					{
+						Path:     path,
+						HostPath: filepath.Join(l.devRoot, path),
+					},
+				},
+			},
+		}
+		deviceSpecs = append(deviceSpecs, deviceSpec)
+	}
+	return deviceSpecs, nil
+}
+
+// GetGPUDeviceEdits is unsupported for the imexlib specs
+func (l *imexlib) GetGPUDeviceEdits(device.Device) (*cdi.ContainerEdits, error) {
+	return nil, fmt.Errorf("GetGPUDeviceEdits is not supported")
+}
+
+// GetGPUDeviceSpecs is unsupported for the imexlib specs
+func (l *imexlib) GetGPUDeviceSpecs(int, device.Device) ([]specs.Device, error) {
+	return nil, fmt.Errorf("GetGPUDeviceSpecs is not supported")
+}
+
+// GetMIGDeviceEdits is unsupported for the imexlib specs
+func (l *imexlib) GetMIGDeviceEdits(device.Device, device.MigDevice) (*cdi.ContainerEdits, error) {
+	return nil, fmt.Errorf("GetMIGDeviceEdits is not supported")
+}
+
+// GetMIGDeviceSpecs is unsupported for the imexlib specs
+func (l *imexlib) GetMIGDeviceSpecs(int, device.Device, int, device.MigDevice) ([]specs.Device, error) {
+	return nil, fmt.Errorf("GetMIGDeviceSpecs is not supported")
+}