Match device driver on name and ignore capabilities

This change ignores requested capabilities when a driver is explicitly
requested. This simplifies the logic for selecting a driver and means
that users need not spefify redundant capabilities.

With the exception of the catch-all "gpu" capability the remaining
capabilities are only relevant for the "nvidia" driver.

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

api/swagger.yaml

@@ -293,6 +293,11 @@ definitions:
     description: "A request for devices to be sent to device drivers"
     properties:
       Driver:
+        description: |
+          The name of the device driver to use for this request.
+
+          Note that if this is specified the capabilities are ignored when
+          selecting a device driver.
         type: "string"
         example: "nvidia"
       Count:
@@ -309,6 +314,12 @@ definitions:
       Capabilities:
         description: |
           A list of capabilities; an OR list of AND lists of capabilities.
+
+          Note that if a driver is specified the capabilities have no effect on
+          selecting a driver as the driver name is used directly.
+
+          Note that if no driver is specified the capabilities are used to
+          select a driver with the required capabilities.
         type: "array"
         items:
           type: "array"

daemon/devices.go

@@ -3,6 +3,7 @@ package daemon
 import (
 	"context"
 
+	"github.com/containerd/log"
 	"github.com/moby/moby/api/types/container"
 	"github.com/moby/moby/api/types/system"
 	"github.com/moby/moby/v2/daemon/config"
@@ -39,26 +40,33 @@ func registerDeviceDriver(name string, d *deviceDriver) {
 
 func (daemon *Daemon) handleDevice(req container.DeviceRequest, spec *specs.Spec) error {
 	if req.Driver == "" {
-		for _, dd := range deviceDrivers {
+		// If no driver is explicitly requested, we iterate over the registered
+		// drivers and attempt to match on capabilities.
+		for driver, dd := range deviceDrivers {
 			if selected := dd.capset.Match(req.Capabilities); selected != nil {
+				log.G(context.TODO()).WithFields(log.Fields{
+					"driver": driver,
+					"capabilities": map[string]any{
+						"requested": req.Capabilities,
+						"selected":  selected,
+					},
+				}).Debugf("Selecting device driver by capabilities")
 				return dd.updateSpec(spec, &deviceInstance{req: req, selectedCaps: selected})
 			}
 		}
 	} else if dd := deviceDrivers[req.Driver]; dd != nil {
-		// We add a special case for the CDI driver here as the cdi driver does
+		selected := dd.capset.Match(req.Capabilities)
-		// not distinguish between capabilities.
+		// If a driver is explicitly requested and registered, then we use the
-		// Furthermore, the "OR" and "AND" matching logic for the capability
+		// specified driver, ignoring the capabilities.
-		// sets requires that a dummy capability be specified when constructing a
+		log.G(context.TODO()).WithFields(log.Fields{
-		// DeviceRequest.
+			"driver": req.Driver,
-		// This workaround can be removed once these device driver are
+			"capabilities": map[string]any{
-		// refactored to be plugins, with each driver implementing its own
+				"requested": req.Capabilities,
-		// matching logic, for example.
+				"selected":  selected,
-		if req.Driver == "cdi" {
+			},
-			return dd.updateSpec(spec, &deviceInstance{req: req})
+		}).Debugf("Selecting device driver by driver name; possibly ignoring capabilities")
-		}
+		return dd.updateSpec(spec, &deviceInstance{req: req, selectedCaps: selected})
-		if selected := dd.capset.Match(req.Capabilities); selected != nil {
-			return dd.updateSpec(spec, &deviceInstance{req: req, selectedCaps: selected})
-		}
 	}
+
 	return incompatibleDeviceRequest{req.Driver, req.Capabilities}
 }