chore(usbgadget): update usbgadget config only when needed (#474)

2026-01-20 02:04:15 +01:00 · 2025-05-19 21:48:43 +02:00
parent 0a4a1af80e
commit 7a9fb7cbb1
14 changed files with 1357 additions and 221 deletions
--- a/internal/usbgadget/config_tx.go
+++ b/internal/usbgadget/config_tx.go
@@ -0,0 +1,329 @@
+package usbgadget
+
+import (
+	"fmt"
+	"path"
+	"path/filepath"
+	"sort"
+
+	"github.com/rs/zerolog"
+)
+
+// no os package should occur in this file
+
+type UsbGadgetTransaction struct {
+	c *ChangeSet
+
+	// below are the fields that are needed to be set by the caller
+	log                       *zerolog.Logger
+	udc                       string
+	dwc3Path                  string
+	kvmGadgetPath             string
+	configC1Path              string
+	orderedConfigItems        orderedGadgetConfigItems
+	isGadgetConfigItemEnabled func(key string) bool
+
+	reorderSymlinkChanges *RequestedFileChange
+}
+
+func (u *UsbGadget) newUsbGadgetTransaction(lock bool) error {
+	if lock {
+		u.txLock.Lock()
+		defer u.txLock.Unlock()
+	}
+
+	if u.tx != nil {
+		return fmt.Errorf("transaction already exists")
+	}
+
+	tx := &UsbGadgetTransaction{
+		c:                         &ChangeSet{},
+		log:                       u.log,
+		udc:                       u.udc,
+		dwc3Path:                  dwc3Path,
+		kvmGadgetPath:             u.kvmGadgetPath,
+		configC1Path:              u.configC1Path,
+		orderedConfigItems:        u.getOrderedConfigItems(),
+		isGadgetConfigItemEnabled: u.isGadgetConfigItemEnabled,
+	}
+	u.tx = tx
+
+	return nil
+}
+
+func (u *UsbGadget) WithTransaction(fn func() error) error {
+	u.txLock.Lock()
+	defer u.txLock.Unlock()
+
+	err := u.newUsbGadgetTransaction(false)
+	if err != nil {
+		u.log.Error().Err(err).Msg("failed to create transaction")
+		return err
+	}
+	if err := fn(); err != nil {
+		u.log.Error().Err(err).Msg("transaction failed")
+		return err
+	}
+	result := u.tx.Commit()
+	u.tx = nil
+
+	return result
+}
+
+func (tx *UsbGadgetTransaction) addFileChange(component string, change RequestedFileChange) string {
+	change.Component = component
+	tx.c.AddFileChangeStruct(change)
+
+	key := change.Key
+	if key == "" {
+		key = change.Path
+	}
+	return key
+}
+
+func (tx *UsbGadgetTransaction) mkdirAll(component string, path string, description string) string {
+	return tx.addFileChange(component, RequestedFileChange{
+		Path:          path,
+		ExpectedState: FileStateDirectory,
+		Description:   description,
+	})
+}
+
+func (tx *UsbGadgetTransaction) removeFile(component string, path string, description string) string {
+	return tx.addFileChange(component, RequestedFileChange{
+		Path:          path,
+		ExpectedState: FileStateAbsent,
+		Description:   description,
+	})
+}
+
+func (tx *UsbGadgetTransaction) Commit() error {
+	tx.addFileChange("gadget-finalize", *tx.reorderSymlinkChanges)
+
+	err := tx.c.Apply()
+	if err != nil {
+		tx.log.Error().Err(err).Msg("failed to update usbgadget configuration")
+		return err
+	}
+	tx.log.Info().Msg("usbgadget configuration updated")
+	return nil
+}
+
+func (u *UsbGadget) getOrderedConfigItems() orderedGadgetConfigItems {
+	items := make([]gadgetConfigItemWithKey, 0)
+	for key, item := range u.configMap {
+		items = append(items, gadgetConfigItemWithKey{key, item})
+	}
+
+	sort.Slice(items, func(i, j int) bool {
+		return items[i].item.order < items[j].item.order
+	})
+
+	return items
+}
+
+func (tx *UsbGadgetTransaction) MountConfigFS() {
+	tx.addFileChange("gadget", RequestedFileChange{
+		Path:          configFSPath,
+		ExpectedState: FileStateMountedConfigFS,
+		Description:   "mount configfs",
+	})
+}
+
+func (tx *UsbGadgetTransaction) CreateConfigPath() {
+	tx.mkdirAll("gadget", tx.configC1Path, "create config path")
+}
+
+func (tx *UsbGadgetTransaction) WriteGadgetConfig() {
+	// create kvm gadget path
+	tx.mkdirAll("gadget", tx.kvmGadgetPath, "create kvm gadget path")
+
+	deps := make([]string, 0)
+
+	for _, val := range tx.orderedConfigItems {
+		key := val.key
+		item := val.item
+
+		// check if the item is enabled in the config
+		if !tx.isGadgetConfigItemEnabled(key) {
+			tx.DisableGadgetItemConfig(item)
+			continue
+		}
+		deps = tx.writeGadgetItemConfig(item, deps)
+	}
+
+	tx.WriteUDC()
+}
+
+func (tx *UsbGadgetTransaction) getDisableKeys() []string {
+	disableKeys := make([]string, 0)
+	for _, item := range tx.orderedConfigItems {
+		if !tx.isGadgetConfigItemEnabled(item.key) {
+			continue
+		}
+		if item.item.configPath == nil || item.item.configAttrs != nil {
+			continue
+		}
+
+		disableKeys = append(disableKeys, fmt.Sprintf("disable-%s", item.item.device))
+	}
+	return disableKeys
+}
+
+func (tx *UsbGadgetTransaction) DisableGadgetItemConfig(item gadgetConfigItem) {
+	// remove symlink if exists
+	if item.configPath == nil {
+		return
+	}
+
+	configPath := joinPath(tx.configC1Path, item.configPath)
+	_ = tx.removeFile("gadget", configPath, "remove symlink: disable gadget config")
+}
+
+func (tx *UsbGadgetTransaction) writeGadgetItemConfig(item gadgetConfigItem, deps []string) []string {
+	component := item.device
+
+	// create directory for the item
+	files := make([]string, 0)
+	files = append(files, deps...)
+
+	gadgetItemPath := joinPath(tx.kvmGadgetPath, item.path)
+	files = append(files, tx.mkdirAll(component, gadgetItemPath, "create gadget item directory"))
+
+	beforeChange := make([]string, 0)
+	disableGadgetItemKey := fmt.Sprintf("disable-%s", item.device)
+	if item.configPath != nil && item.configAttrs == nil {
+		beforeChange = append(beforeChange, tx.getDisableKeys()...)
+	}
+
+	if len(item.attrs) > 0 {
+		// write attributes for the item
+		files = append(files, tx.writeGadgetAttrs(
+			gadgetItemPath,
+			item.attrs,
+			component,
+			beforeChange,
+		)...)
+	}
+
+	// write report descriptor if available
+	reportDescPath := path.Join(gadgetItemPath, "report_desc")
+	if item.reportDesc != nil {
+		tx.addFileChange(component, RequestedFileChange{
+			Path:            reportDescPath,
+			ExpectedState:   FileStateFileContentMatch,
+			ExpectedContent: item.reportDesc,
+			Description:     "write report descriptor",
+			BeforeChange:    beforeChange,
+			DependsOn:       files,
+		})
+	} else {
+		tx.addFileChange(component, RequestedFileChange{
+			Path:          reportDescPath,
+			ExpectedState: FileStateAbsent,
+			Description:   "remove report descriptor",
+			BeforeChange:  beforeChange,
+			DependsOn:     files,
+		})
+	}
+	files = append(files, reportDescPath)
+
+	// create config directory if configAttrs are set
+	if len(item.configAttrs) > 0 {
+		configItemPath := joinPath(tx.configC1Path, item.configPath)
+		tx.mkdirAll(component, configItemPath, "create config item directory")
+		files = append(files, tx.writeGadgetAttrs(
+			configItemPath,
+			item.configAttrs,
+			component,
+			beforeChange,
+		)...)
+	}
+
+	// create symlink if configPath is set
+	if item.configPath != nil && item.configAttrs == nil {
+		configPath := joinPath(tx.configC1Path, item.configPath)
+
+		// the change will be only applied by `beforeChange`
+		tx.addFileChange(component, RequestedFileChange{
+			Key:           disableGadgetItemKey,
+			Path:          configPath,
+			ExpectedState: FileStateAbsent,
+			When:          "beforeChange", // TODO: make it more flexible
+			Description:   "remove symlink",
+		})
+
+		tx.addReorderSymlinkChange(configPath, gadgetItemPath, files)
+	}
+
+	return files
+}
+
+func (tx *UsbGadgetTransaction) writeGadgetAttrs(basePath string, attrs gadgetAttributes, component string, beforeChange []string) (files []string) {
+	files = make([]string, 0)
+	for key, val := range attrs {
+		filePath := filepath.Join(basePath, key)
+		tx.addFileChange(component, RequestedFileChange{
+			Path:            filePath,
+			ExpectedState:   FileStateFileContentMatch,
+			ExpectedContent: []byte(val),
+			Description:     "write gadget attribute",
+			DependsOn:       []string{basePath},
+			BeforeChange:    beforeChange,
+		})
+		files = append(files, filePath)
+	}
+	return files
+}
+
+func (tx *UsbGadgetTransaction) addReorderSymlinkChange(path string, target string, deps []string) {
+	tx.log.Trace().Str("path", path).Str("target", target).Msg("add reorder symlink change")
+
+	if tx.reorderSymlinkChanges == nil {
+		tx.reorderSymlinkChanges = &RequestedFileChange{
+			Component:     "gadget-finalize",
+			Key:           "reorder-symlinks",
+			Path:          tx.configC1Path,
+			ExpectedState: FileStateSymlinkInOrderConfigFS,
+			Description:   "order symlinks",
+			ParamSymlinks: []symlink{},
+		}
+	}
+
+	tx.reorderSymlinkChanges.DependsOn = append(tx.reorderSymlinkChanges.DependsOn, deps...)
+	tx.reorderSymlinkChanges.ParamSymlinks = append(tx.reorderSymlinkChanges.ParamSymlinks, symlink{
+		Path:   path,
+		Target: target,
+	})
+}
+
+func (tx *UsbGadgetTransaction) WriteUDC() {
+	// bound the gadget to a UDC (USB Device Controller)
+	path := path.Join(tx.kvmGadgetPath, "UDC")
+	tx.addFileChange("udc", RequestedFileChange{
+		Path:            path,
+		ExpectedState:   FileStateFileContentMatch,
+		ExpectedContent: []byte(tx.udc),
+		DependsOn:       []string{"reorder-symlinks"},
+		Description:     "write UDC",
+	})
+}
+
+func (tx *UsbGadgetTransaction) RebindUsb(ignoreUnbindError bool) {
+	// remove the gadget from the UDC
+	tx.addFileChange("udc", RequestedFileChange{
+		Path:            path.Join(tx.dwc3Path, "unbind"),
+		ExpectedState:   FileStateFileWrite,
+		ExpectedContent: []byte(tx.udc),
+		Description:     "unbind UDC",
+	})
+	// bind the gadget to the UDC
+	tx.addFileChange("udc", RequestedFileChange{
+		Path:            path.Join(tx.dwc3Path, "bind"),
+		ExpectedState:   FileStateFileWrite,
+		ExpectedContent: []byte(tx.udc),
+		Description:     "bind UDC",
+		DependsOn:       []string{path.Join(tx.dwc3Path, "unbind")},
+		IgnoreErrors:    ignoreUnbindError,
+	})
+}