Add internal/info/proc/devices package to read device majors

This change adds basic functionality to process the /proc/devices
file to extract device majors.

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

internal/info/proc/devices/devices.go

@@ -0,0 +1,125 @@
+/*
+# Copyright (c) 2021, NVIDIA CORPORATION.  All rights reserved.
+#
+# 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 devices
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+)
+
+// Device major numbers and device names for NVIDIA devices
+const (
+	NVIDIAUVMMinor      = 0
+	NVIDIAUVMToolsMinor = 1
+	NVIDIACTLMinor      = 255
+	NVIDIAModesetMinor  = 254
+
+	NVIDIAFrontend = Name("nvidia-frontend")
+	NVIDIAGPU      = NVIDIAFrontend
+	NVIDIACaps     = Name("nvidia-caps")
+	NVIDIAUVM      = Name("nvidia-uvm")
+
+	procDevicesPath    = "/proc/devices"
+	nvidiaDevicePrefix = "nvidia"
+)
+
+// Name represents the name of a device as specified under /proc/devices
+type Name string
+
+// Major represents a device major as specified under /proc/devices
+type Major int
+
+// Devices represents the set of devices under /proc/devices
+//
+//go:generate moq -stub -out devices_mock.go . Devices
+type Devices interface {
+	Exists(Name) bool
+	Get(Name) (Major, bool)
+}
+
+type devices map[Name]Major
+
+var _ Devices = devices(nil)
+
+// Exists checks if a Device with a given name exists or not
+func (d devices) Exists(name Name) bool {
+	_, exists := d[name]
+	return exists
+}
+
+// Get a Device from Devices
+func (d devices) Get(name Name) (Major, bool) {
+	device, exists := d[name]
+	return device, exists
+}
+
+// GetNVIDIADevices returns the set of NVIDIA Devices on the machine
+func GetNVIDIADevices() (Devices, error) {
+	devicesFile, err := os.Open(procDevicesPath)
+	if os.IsNotExist(err) {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("error opening devices file: %v", err)
+	}
+	defer devicesFile.Close()
+
+	return nvidiaDeviceFrom(devicesFile), nil
+}
+
+func nvidiaDeviceFrom(reader io.Reader) devices {
+	allDevices := devicesFrom(reader)
+	nvidiaDevices := make(devices)
+	for n, d := range allDevices {
+		if !strings.HasPrefix(string(n), nvidiaDevicePrefix) {
+			continue
+		}
+		nvidiaDevices[n] = d
+	}
+
+	return nvidiaDevices
+}
+
+func devicesFrom(reader io.Reader) devices {
+	allDevices := make(devices)
+	scanner := bufio.NewScanner(reader)
+	for scanner.Scan() {
+		device, major, err := processProcDeviceLine(scanner.Text())
+		if err != nil {
+			continue
+		}
+		allDevices[device] = major
+	}
+	return allDevices
+}
+
+func processProcDeviceLine(line string) (Name, Major, error) {
+	trimmed := strings.TrimSpace(line)
+
+	var name Name
+	var major Major
+
+	n, _ := fmt.Sscanf(trimmed, "%d %s", &major, &name)
+	if n == 2 {
+		return name, major, nil
+	}
+
+	return "", 0, fmt.Errorf("unparsable line: %v", line)
+}

internal/info/proc/devices/devices_mock.go

@@ -0,0 +1,125 @@
+// Code generated by moq; DO NOT EDIT.
+// github.com/matryer/moq
+
+package devices
+
+import (
+	"sync"
+)
+
+// Ensure, that DevicesMock does implement Devices.
+// If this is not the case, regenerate this file with moq.
+var _ Devices = &DevicesMock{}
+
+// DevicesMock is a mock implementation of Devices.
+//
+//	func TestSomethingThatUsesDevices(t *testing.T) {
+//
+//		// make and configure a mocked Devices
+//		mockedDevices := &DevicesMock{
+//			ExistsFunc: func(name Name) bool {
+//				panic("mock out the Exists method")
+//			},
+//			GetFunc: func(name Name) (Major, bool) {
+//				panic("mock out the Get method")
+//			},
+//		}
+//
+//		// use mockedDevices in code that requires Devices
+//		// and then make assertions.
+//
+//	}
+type DevicesMock struct {
+	// ExistsFunc mocks the Exists method.
+	ExistsFunc func(name Name) bool
+
+	// GetFunc mocks the Get method.
+	GetFunc func(name Name) (Major, bool)
+
+	// calls tracks calls to the methods.
+	calls struct {
+		// Exists holds details about calls to the Exists method.
+		Exists []struct {
+			// Name is the name argument value.
+			Name Name
+		}
+		// Get holds details about calls to the Get method.
+		Get []struct {
+			// Name is the name argument value.
+			Name Name
+		}
+	}
+	lockExists sync.RWMutex
+	lockGet    sync.RWMutex
+}
+
+// Exists calls ExistsFunc.
+func (mock *DevicesMock) Exists(name Name) bool {
+	callInfo := struct {
+		Name Name
+	}{
+		Name: name,
+	}
+	mock.lockExists.Lock()
+	mock.calls.Exists = append(mock.calls.Exists, callInfo)
+	mock.lockExists.Unlock()
+	if mock.ExistsFunc == nil {
+		var (
+			bOut bool
+		)
+		return bOut
+	}
+	return mock.ExistsFunc(name)
+}
+
+// ExistsCalls gets all the calls that were made to Exists.
+// Check the length with:
+//
+//	len(mockedDevices.ExistsCalls())
+func (mock *DevicesMock) ExistsCalls() []struct {
+	Name Name
+} {
+	var calls []struct {
+		Name Name
+	}
+	mock.lockExists.RLock()
+	calls = mock.calls.Exists
+	mock.lockExists.RUnlock()
+	return calls
+}
+
+// Get calls GetFunc.
+func (mock *DevicesMock) Get(name Name) (Major, bool) {
+	callInfo := struct {
+		Name Name
+	}{
+		Name: name,
+	}
+	mock.lockGet.Lock()
+	mock.calls.Get = append(mock.calls.Get, callInfo)
+	mock.lockGet.Unlock()
+	if mock.GetFunc == nil {
+		var (
+			majorOut Major
+			bOut     bool
+		)
+		return majorOut, bOut
+	}
+	return mock.GetFunc(name)
+}
+
+// GetCalls gets all the calls that were made to Get.
+// Check the length with:
+//
+//	len(mockedDevices.GetCalls())
+func (mock *DevicesMock) GetCalls() []struct {
+	Name Name
+} {
+	var calls []struct {
+		Name Name
+	}
+	mock.lockGet.RLock()
+	calls = mock.calls.Get
+	mock.lockGet.RUnlock()
+	return calls
+}

internal/info/proc/devices/devices_test.go

@@ -0,0 +1,102 @@
+/*
+# Copyright (c) 2021, NVIDIA CORPORATION.  All rights reserved.
+#
+# 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 devices
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNvidiaDevices(t *testing.T) {
+	devices := map[Name]Major{
+		"nvidia-frontend": 195,
+		"nvidia-nvlink":   234,
+		"nvidia-caps":     235,
+		"nvidia-uvm":      510,
+		"nvidia-nvswitch": 511,
+	}
+
+	nvidiaDevices := testDevices(devices)
+	for name, major := range devices {
+		device, exists := nvidiaDevices.Get(name)
+		require.True(t, exists, "Unexpected missing device")
+		require.Equal(t, device, major, "Unexpected device major")
+	}
+	_, exists := nvidiaDevices.Get("bogus")
+	require.False(t, exists, "Unexpected 'bogus' device found")
+}
+
+func TestProcessDeviceFile(t *testing.T) {
+	testCases := []struct {
+		lines    []string
+		expected devices
+	}{
+		{[]string{}, make(devices)},
+		{[]string{"Not a valid line:"}, make(devices)},
+		{[]string{"195 nvidia-frontend"}, devices{"nvidia-frontend": 195}},
+		{[]string{"195 nvidia-frontend", "235 nvidia-caps"}, devices{"nvidia-frontend": 195, "nvidia-caps": 235}},
+		{[]string{"  195 nvidia-frontend"}, devices{"nvidia-frontend": 195}},
+		{[]string{"Not a valid line:", "", "195 nvidia-frontend"}, devices{"nvidia-frontend": 195}},
+		{[]string{"195 not-nvidia-frontend"}, make(devices)},
+	}
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("testcase %d", i), func(t *testing.T) {
+			contents := strings.NewReader(strings.Join(tc.lines, "\n"))
+			d := nvidiaDeviceFrom(contents)
+
+			require.EqualValues(t, tc.expected, d)
+		})
+	}
+}
+
+func TestProcessDeviceFileLine(t *testing.T) {
+	testCases := []struct {
+		line  string
+		name  Name
+		major Major
+		err   bool
+	}{
+		{"", "", 0, true},
+		{"0", "", 0, true},
+		{"notint nvidia-frontend", "", 0, true},
+		{"195 nvidia-frontend", "nvidia-frontend", 195, false},
+		{"   195 nvidia-frontend", "nvidia-frontend", 195, false},
+	}
+
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("testcase %d", i), func(t *testing.T) {
+			name, major, err := processProcDeviceLine(tc.line)
+
+			require.Equal(t, tc.name, name)
+			require.Equal(t, tc.major, major)
+			if tc.err {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+
+		})
+	}
+}
+
+// testDevices creates a set of test NVIDIA devices
+func testDevices(d map[Name]Major) Devices {
+	return devices(d)
+}