src.com.android.server.ExtconUEventObserver Maven / Gradle / Ivy
/*
* Copyright (C) 2018 The Android Open Source Project
*
* 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 com.android.server;
import android.annotation.Nullable;
import android.os.UEventObserver;
import android.util.ArrayMap;
import android.util.Slog;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.regex.Pattern;
/**
* A specialized UEventObserver that receives UEvents from the kernel for devices in the {@code
* /sys/class/extcon}. directory
*
* Subclass ExtconUEventObserver, implementing {@link #onUEvent(ExtconInfo, UEvent)}, then call
* startObserving() with a ExtconInfo to observe. The UEvent thread will then call your onUEvent()
* method when a UEvent occurs that matches the path of your ExtconInfos.
*
*
Call stopObserving() to stop receiving UEvents.
*
*
There is only one UEvent thread per process, even if that process has multiple UEventObserver
* subclass instances. The UEvent thread starts when the startObserving() is called for the first
* time in that process. Once started the UEvent thread will not stop (although it can stop
* notifying UEventObserver's via stopObserving()).
*
* @hide
*/
public abstract class ExtconUEventObserver extends UEventObserver {
private static final String TAG = "ExtconUEventObserver";
private static final boolean LOG = false;
private static final String SELINUX_POLICIES_NEED_TO_BE_CHANGED =
"This probably means the selinux policies need to be changed.";
private final Map mExtconInfos = new ArrayMap<>();
@Override
public final void onUEvent(UEvent event) {
String devPath = event.get("DEVPATH");
ExtconInfo info = mExtconInfos.get(devPath);
if (info != null) {
onUEvent(info, event);
} else {
Slog.w(TAG, "No match found for DEVPATH of " + event + " in " + mExtconInfos);
}
}
/**
* Subclasses of ExtconUEventObserver should override this method to handle UEvents.
*
* @param extconInfo that matches the {@code DEVPATH} of {@code event}
* @param event the event
*/
protected abstract void onUEvent(ExtconInfo extconInfo, UEvent event);
/** Starts observing {@link ExtconInfo#getDevicePath()}. */
public void startObserving(ExtconInfo extconInfo) {
String devicePath = extconInfo.getDevicePath();
if (devicePath == null) {
Slog.wtf(TAG, "Unable to start observing " + extconInfo.getName()
+ " because the device path is null. " + SELINUX_POLICIES_NEED_TO_BE_CHANGED);
} else {
mExtconInfos.put(devicePath, extconInfo);
if (LOG) Slog.v(TAG, "Observing " + devicePath);
startObserving("DEVPATH=" + devicePath);
}
}
/** An External Connection to watch. */
public static final class ExtconInfo {
private static final String TAG = "ExtconInfo";
/** Returns a new list of all external connections whose name matches {@code regex}. */
public static List getExtconInfos(@Nullable String regex) {
if (!extconExists()) {
return new ArrayList<>(0); // Always return a new list.
}
Pattern p = regex == null ? null : Pattern.compile(regex);
File file = new File("/sys/class/extcon");
File[] files = file.listFiles();
if (files == null) {
Slog.wtf(TAG, file + " exists " + file.exists() + " isDir " + file.isDirectory()
+ " but listFiles returns null. "
+ SELINUX_POLICIES_NEED_TO_BE_CHANGED);
return new ArrayList<>(0); // Always return a new list.
} else {
ArrayList list = new ArrayList(files.length);
for (File f : files) {
String name = f.getName();
if (p == null || p.matcher(name).matches()) {
ExtconInfo uei = new ExtconInfo(name);
list.add(uei);
if (LOG) Slog.d(TAG, name + " matches " + regex);
} else {
if (LOG) Slog.d(TAG, name + " does not match " + regex);
}
}
return list;
}
}
private final String mName;
public ExtconInfo(String name) {
mName = name;
}
/** The name of the external connection */
public String getName() {
return mName;
}
/**
* The path to the device for this external connection.
*
* NOTE getting this path involves resolving a symlink.
*
* @return the device path, or null if it not found.
*/
@Nullable
public String getDevicePath() {
try {
String extconPath = String.format(Locale.US, "/sys/class/extcon/%s", mName);
File devPath = new File(extconPath);
if (devPath.exists()) {
String canonicalPath = devPath.getCanonicalPath();
int start = canonicalPath.indexOf("/devices");
return canonicalPath.substring(start);
}
return null;
} catch (IOException e) {
Slog.e(TAG, "Could not get the extcon device path for " + mName, e);
return null;
}
}
/** The path to the state file */
public String getStatePath() {
return String.format(Locale.US, "/sys/class/extcon/%s/state", mName);
}
}
/** Does the {@code /sys/class/extcon/} directory exist */
public static boolean namedExtconDirExists(String name) {
File extconDir = new File("/sys/class/extcon/" + name);
return extconDir.exists() && extconDir.isDirectory();
}
/** Does the {@code /sys/class/extcon} directory exist */
public static boolean extconExists() {
File extconDir = new File("/sys/class/extcon");
return extconDir.exists() && extconDir.isDirectory();
}
}