用inotify机制监测 /dev/bus/usb文件夹下面的变化,对添加的节点的内存进行解析,从而获得添加/删除 设备的改变。
我的一个疑惑是:当用USB反向充电时,有一种情况是:一侧是 source,device组合,另外一侧是 sink ,host 组合,此时mtp,仅充电、ptp等选项界面会在sink ,host 组合侧出现(基本的规律是,sink侧会出现该界面)。此时进行,mtp等选项切换时,两侧的UsbHostManager均不能探测到usb config的变化。为什么?
该界面是设置当设备当作从设备时,该设备作为mtp,ptp设备功能的设置。所以虽然能设置成功,但是并没有连接成功,因为当前该设备组合是( sink ,host)是作为一个主设备而存在的。要连接成功,可以把当前设备切换成从设备。或者在对端设置成对应的功能(mtp,ptp等),此时对端虽然没有选择界面弹出(这是android的一个BUG),但是可以通过svc usb setFunctions mtp等命令切换功能。
frameworks/base/services/usb/java/com/android/server/usb/UsbHostManager.java
public void systemReady() {
synchronized (mLock) {
// Create a thread to call into native code to wait for USB host events.
// This thread will call us back on usbDeviceAdded and usbDeviceRemoved.
Runnable runnable = this::monitorUsbHostBus;
new Thread(null, runnable, "UsbService host thread").start();
}
}
private native void monitorUsbHostBus();
private native ParcelFileDescriptor nativeOpenDevice(String deviceAddress);
frameworks/base/services/core/jni/com_android_server_UsbHostManager.cpp
static const JNINativeMethod method_table[] = {
{ "monitorUsbHostBus", "()V", (void*)android_server_UsbHostManager_monitorUsbHostBus },
{ "nativeOpenDevice", "(Ljava/lang/String;)Landroid/os/ParcelFileDescriptor;",
(void*)android_server_UsbHostManager_openDevice },
};
static void android_server_UsbHostManager_monitorUsbHostBus(JNIEnv* /* env */, jobject thiz)
{
struct usb_host_context* context = usb_host_init();
if (!context) {
ALOGE("usb_host_init failed");
return;
}
// this will never return so it is safe to pass thiz directly
usb_host_run(context, usb_device_added, usb_device_removed, NULL, (void *)thiz);
}
static int usb_device_added(const char *devAddress, void* clientData) {
struct usb_device *device = usb_device_open(devAddress); //打开设备节点,具体看后面的实现
if (!device) {
ALOGE("usb_device_open failed\n");
return 0;
}
const usb_device_descriptor* deviceDesc = usb_device_get_device_descriptor(device);
int classID = deviceDesc->bDeviceClass;
int subClassID = deviceDesc->bDeviceSubClass;
// get the raw descriptors
int numBytes = usb_device_get_descriptors_length(device);
if (numBytes > 0) {
JNIEnv* env = AndroidRuntime::getJNIEnv();
jobject thiz = (jobject)clientData;
jstring deviceAddress = env->NewStringUTF(devAddress);
jbyteArray descriptorsArray = env->NewByteArray(numBytes);
const jbyte* rawDescriptors = (const jbyte*)usb_device_get_raw_descriptors(device);
env->SetByteArrayRegion(descriptorsArray, 0, numBytes, rawDescriptors);
env->CallBooleanMethod(thiz, method_usbDeviceAdded,
deviceAddress, classID, subClassID, descriptorsArray);
env->DeleteLocalRef(descriptorsArray);
env->DeleteLocalRef(deviceAddress);
checkAndClearExceptionFromCallback(env, __FUNCTION__);
} else {
// TODO return an error code here?
ALOGE("error reading descriptors\n");
}
usb_device_close(device);
return 0;
}
static int usb_device_removed(const char *devAddress, void* clientData) {
JNIEnv* env = AndroidRuntime::getJNIEnv();
jobject thiz = (jobject)clientData;
jstring deviceAddress = env->NewStringUTF(devAddress);
env->CallVoidMethod(thiz, method_usbDeviceRemoved, deviceAddress);
env->DeleteLocalRef(deviceAddress);
checkAndClearExceptionFromCallback(env, __FUNCTION__);
return 0;
}
system/core/libusbhost/usbhost.c
struct usb_host_context *usb_host_init()
{
struct usb_host_context *context = calloc(1, sizeof(struct usb_host_context));
if (!context) {
fprintf(stderr, "out of memory in usb_host_context\n");
return NULL;
}
//inotify是文件系统变化通知机制,在监听到文件系统变化后,会向相应的应用程序发送事件
//inotify_add_watch 添加要监控的路径
context->fd = inotify_init();
if (context->fd < 0) {
fprintf(stderr, "inotify_init failed\n");
free(context);
return NULL;
}
return context;
}
void usb_host_run(struct usb_host_context *context,
usb_device_added_cb added_cb,
usb_device_removed_cb removed_cb,
usb_discovery_done_cb discovery_done_cb,
void *client_data)
{
int done;
done = usb_host_load(context, added_cb, removed_cb, discovery_done_cb, client_data);
while (!done) {
done = usb_host_read_event(context);
}
} /* usb_host_run() */
#define DEV_DIR "/dev"
#define DEV_BUS_DIR DEV_DIR "/bus"
#define USB_FS_DIR DEV_BUS_DIR "/usb"
#define USB_FS_ID_SCANNER USB_FS_DIR "/%d/%d"
#define USB_FS_ID_FORMAT USB_FS_DIR "/%03d/%03d"
int usb_host_load(struct usb_host_context *context,
usb_device_added_cb added_cb,
usb_device_removed_cb removed_cb,
usb_discovery_done_cb discovery_done_cb,
void *client_data)
{
int done = 0;
int i;
context->cb_added = added_cb;
context->cb_removed = removed_cb;
context->data = client_data;
D("Created device discovery thread\n");
/* watch for files added and deleted within USB_FS_DIR */
context->wddbus = -1;
for (i = 0; i < MAX_USBFS_WD_COUNT; i++)
context->wds[i] = -1;
/* watch the root for new subdirectories */
context->wdd = inotify_add_watch(context->fd, DEV_DIR, IN_CREATE | IN_DELETE);
if (context->wdd < 0) {
fprintf(stderr, "inotify_add_watch failed\n");
if (discovery_done_cb)
discovery_done_cb(client_data);
return done;
}
watch_existing_subdirs(context, context->wds, MAX_USBFS_WD_COUNT);
/* check for existing devices first, after we have inotify set up */
done = find_existing_devices(added_cb, client_data);
if (discovery_done_cb)
done |= discovery_done_cb(client_data);
return done;
} /* usb_host_load() */
static void watch_existing_subdirs(struct usb_host_context *context,
int *wds, int wd_count)
{
char path[100];
int i, ret;
//USB_FS_DIR --> /dev/bus/usb
wds[0] = inotify_add_watch(context->fd, USB_FS_DIR, IN_CREATE | IN_DELETE);
if (wds[0] < 0)
return;
/* watch existing subdirectories of USB_FS_DIR */
for (i = 1; i < wd_count; i++) {
snprintf(path, sizeof(path), USB_FS_DIR "/%03d", i);
ret = inotify_add_watch(context->fd, path, IN_CREATE | IN_DELETE);
if (ret >= 0)
wds[i] = ret;
}
}
static int find_existing_devices_bus(char *busname,
usb_device_added_cb added_cb,
void *client_data)
{
char devname[32];
DIR *devdir;
struct dirent *de;
int done = 0;
devdir = opendir(busname);
if(devdir == 0) return 0;
while ((de = readdir(devdir)) && !done) {
if(badname(de->d_name)) continue;
snprintf(devname, sizeof(devname), "%s/%s", busname, de->d_name);
done = added_cb(devname, client_data);
} // end of devdir while
closedir(devdir);
return done;
}
/* returns true if one of the callbacks indicates we are done */
static int find_existing_devices(usb_device_added_cb added_cb,
void *client_data)
{
char busname[32];
DIR *busdir;
struct dirent *de;
int done = 0;
busdir = opendir(USB_FS_DIR);
if(busdir == 0) return 0;
while ((de = readdir(busdir)) != 0 && !done) {
if(badname(de->d_name)) continue;
snprintf(busname, sizeof(busname), USB_FS_DIR "/%s", de->d_name);
done = find_existing_devices_bus(busname, added_cb,
client_data);
} //end of busdir while
closedir(busdir);
return done;
}
打开设备,读取设备描述符
system/core/libusbhost/usbhost.c
int usb_host_read_event(struct usb_host_context *context)
{
struct inotify_event* event;
char event_buf[512];
char path[100];
int i, ret, done = 0;
int offset = 0;
int wd;
ret = read(context->fd, event_buf, sizeof(event_buf));
if (ret >= (int)sizeof(struct inotify_event)) {
while (offset < ret && !done) {
event = (struct inotify_event*)&event_buf[offset];
done = 0;
wd = event->wd;
if (wd == context->wdd) {
if ((event->mask & IN_CREATE) && !strcmp(event->name, "bus")) {
context->wddbus = inotify_add_watch(context->fd, DEV_BUS_DIR, IN_CREATE | IN_DELETE);
if (context->wddbus < 0) {
done = 1;
} else {
watch_existing_subdirs(context, context->wds, MAX_USBFS_WD_COUNT);
done = find_existing_devices(context->cb_added, context->data);
}
}
} else if (wd == context->wddbus) {
if ((event->mask & IN_CREATE) && !strcmp(event->name, "usb")) {
watch_existing_subdirs(context, context->wds, MAX_USBFS_WD_COUNT);
done = find_existing_devices(context->cb_added, context->data);
} else if ((event->mask & IN_DELETE) && !strcmp(event->name, "usb")) {
for (i = 0; i < MAX_USBFS_WD_COUNT; i++) {
if (context->wds[i] >= 0) {
inotify_rm_watch(context->fd, context->wds[i]);
context->wds[i] = -1;
}
}
}
} else if (wd == context->wds[0]) {
i = atoi(event->name);
snprintf(path, sizeof(path), USB_FS_DIR "/%s", event->name);
D("%s subdirectory %s: index: %d\n", (event->mask & IN_CREATE) ?
"new" : "gone", path, i);
if (i > 0 && i < MAX_USBFS_WD_COUNT) {
int local_ret = 0;
if (event->mask & IN_CREATE) {
local_ret = inotify_add_watch(context->fd, path,
IN_CREATE | IN_DELETE);
if (local_ret >= 0)
context->wds[i] = local_ret;
done = find_existing_devices_bus(path, context->cb_added,
context->data);
} else if (event->mask & IN_DELETE) {
inotify_rm_watch(context->fd, context->wds[i]);
context->wds[i] = -1;
}
}
} else {
for (i = 1; (i < MAX_USBFS_WD_COUNT) && !done; i++) {
if (wd == context->wds[i]) {
snprintf(path, sizeof(path), USB_FS_DIR "/%03d/%s", i, event->name);
if (event->mask == IN_CREATE) {
D("new device %s\n", path);
done = context->cb_added(path, context->data);
} else if (event->mask == IN_DELETE) {
D("gone device %s\n", path);
done = context->cb_removed(path, context->data);
}
}
}
}
offset += sizeof(struct inotify_event) + event->len;
}
}
return done;
} /* usb_host_read_event() */
struct usb_device *usb_device_open(const char *dev_name)
{
int fd, attempts, writeable = 1;
const int SLEEP_BETWEEN_ATTEMPTS_US = 100000; /* 100 ms */
const int64_t MAX_ATTEMPTS = 10; /* 1s */
D("usb_device_open %s\n", dev_name);
/* Hack around waiting for permissions to be set on the USB device node.
* Should really be a timeout instead of attempt count, and should REALLY
* be triggered by the perm change via inotify rather than polling.
*/
for (attempts = 0; attempts < MAX_ATTEMPTS; ++attempts) {
if (access(dev_name, R_OK | W_OK) == 0) {
writeable = 1;
break;
} else {
if (access(dev_name, R_OK) == 0) {
/* double check that write permission didn't just come along too! */
writeable = (access(dev_name, R_OK | W_OK) == 0);
break;
}
}
/* not writeable or readable - sleep and try again. */
D("usb_device_open no access sleeping\n");
usleep(SLEEP_BETWEEN_ATTEMPTS_US);
}
if (writeable) {
fd = open(dev_name, O_RDWR);
} else {
fd = open(dev_name, O_RDONLY);
}
D("usb_device_open open returned %d writeable %d errno %d\n", fd, writeable, errno);
if (fd < 0) return NULL;
struct usb_device* result = usb_device_new(dev_name, fd);
if (result)
result->writeable = writeable;
return result;
}
struct usb_device *usb_device_new(const char *dev_name, int fd)
{
struct usb_device *device = calloc(1, sizeof(struct usb_device));
int length;
D("usb_device_new %s fd: %d\n", dev_name, fd);
if (lseek(fd, 0, SEEK_SET) != 0)
goto failed;
length = read(fd, device->desc, sizeof(device->desc));
D("usb_device_new read returned %d errno %d\n", length, errno);
if (length < 0)
goto failed;
strncpy(device->dev_name, dev_name, sizeof(device->dev_name) - 1);
device->fd = fd;
device->desc_length = length;
// assume we are writeable, since usb_device_get_fd will only return writeable fds
device->writeable = 1;
return device;
failed:
// TODO It would be more appropriate to have callers do this
// since this function doesn't "own" this file descriptor.
close(fd);
free(device);
return NULL;
}
USB设备接入报文分析
linux系统路径:/sys/bus/usb/devices
1-0:1.0 2-1.1:1.0 2-1.5:1.0 2-1.5:1.4 3-0:1.0 usb3
2-0:1.0 2-1.1:1.1 2-1.5:1.1 2-1.6 4-0:1.0 usb4
2-1 2-1.1:1.2 2-1.5:1.2 2-1.6:1.0 usb1
2-1.1 2-1.5 2-1.5:1.3 2-1:1.0 usb2
A. 其中usb1、usb2、usb3、usb4表示MCU上接了4条USB总线,即4个USB主机控制器(4个RootHub);
B. 2-1 2号总线的1号端口(物理端口,真实的USB口)设备,即Root Hub
C. 2-1.1 2-1为RootHub,".1"表示RootHub的1号端口设备连接了一个Hub
D. 2-1.1:1.0 2-1为RootHub,".1"表示RootHub的1号端口设备连接了一个Hub,":1"表示1号配置,".0"表示接口号,1个接口即表示一种功能
E. 2-1.1:1.1 2-1为RootHub,".1"表示RootHub的1号端口设备连接了一个Hub,":1"表示1号配置,".1"表示接口号,1个接口即表示一种功能
USB设备报文枚举过程分析:
[10196.531727] ehci_irq: highspeed device disconnect
[10196.536973] ehci_irq: highspeed device connect//1-1 RootHub 1号总线1号端口
[10196.541713] usb 1-1: USB disconnect, device number 2
[10196.543288] ehci_irq: highspeed device disconnect
[17227.295188] ehci_irq: highspeed device connect//2-1 RootHub 2号总线1号端口
[17227.530065] usb 2-1: new high-speed USB device number 2 using sunxi-ehci
[17227.681173] usb 2-1: New USB device found, idVendor=0424, idProduct=2517
[17227.688561] usb 2-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0//2-1:1.0 RootHub 2号总线1号端口,1号配置,0号接口
[17227.699690] hub 2-1:1.0: USB hub found
[17227.704257] hub 2-1:1.0: 7 ports detected//2-1.1 RootHub为2-1,在RootHub 1号端口上级联了hub,并且使用级联hub的1号端口
[17227.990506] usb 2-1.1: new full-speed USB device number 3 using sunxi-ehci
[17228.090313] usb 2-1.1: device descriptor read/64, error -32
[17228.280520] usb 2-1.1: device descriptor read/64, error -32
[17228.470637] usb 2-1.1: new full-speed USB device number 4 using sunxi-ehci
[17228.570508] usb 2-1.1: device descriptor read/64, error -32
[17228.760635] usb 2-1.1: device descriptor read/64, error -32
[17228.950494] usb 2-1.1: new full-speed USB device number 5 using sunxi-ehci
[17229.370289] usb 2-1.1: device not accepting address 5, error -32//2-1.6 RootHub为2-1,在RootHub 1号端口上级联了hub,并且使用级联hub的6号端口
[17229.490500] usb 2-1.6: new high-speed USB device number 7 using sunxi-ehci
[17229.622282] usb 2-1.6: New USB device found, idVendor=0b95, idProduct=772b
[17229.629862] usb 2-1.6: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[17229.638246] usb 2-1.6: Product: AX88772B
[17229.642696] usb 2-1.6: Manufacturer: ASIX Elec. Corp.
[17229.648246] usb 2-1.6: SerialNumber: 000001
[17229.976571] asix 2-1.6:1.0 eth1: register 'asix' at usb-sunxi-ehci-1.6, ASIX AX88772B USB 2.0 Ethernet, 00:0e:c6:87:72:01[17230.220645] usb 2-1.1: new full-speed USB device number 8 using sunxi-ehci
[17230.352509] usb 2-1.1: config 1 has an invalid descriptor of length 0, skipping remainder of the config
[17230.364405] usb 2-1.1: New USB device found, idVendor=0483, idProduct=5740
[17230.372160] usb 2-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[17230.380321] usb 2-1.1: Product: Composite HID CDC
[17230.385501] usb 2-1.1: Manufacturer: STMicroelectronics
[17230.391462] usb 2-1.1: SerialNumber: 395B35563137
[17230.405648] hid-generic 0003:0483:5740.0001: hiddev0,hidraw0: USB HID v1.11 Device [STMicroelectronics Composite HID CDC] on usb-sunxi-ehci-1.1/input0
[17230.425804] cdc_acm 2-1.1:1.1: This device cannot do calls on its own. It is not a modem.
[17230.443286] cdc_acm 2-1.1:1.1: ttyACM0: USB ACM device[17236.810364] usb 2-1.4: new high-speed USB device number 9 using sunxi-ehci
[17236.950567] usb 2-1.4: New USB device found, idVendor=3763, idProduct=3c93
[17236.958148] usb 2-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[17236.966518] usb 2-1.4: Product: Android
[17236.970879] usb 2-1.4: Manufacturer: Android//2-1.4:1.0 RootHub为2-1,在RootHub 1号端口上级联了hub,并且使用级联hub的4号端口,1号配置,0号端口
[17236.978885] option 2-1.4:1.0: GSM modem (1-port) converter detected
[17236.988588] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB0//2-1.4:1.0 RootHub为2-1,在RootHub 1号端口上级联了hub,并且使用级联hub的4号端口,1号配置,1号端口
[17236.997837] option 2-1.4:1.1: GSM modem (1-port) converter detected
[17237.007254] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB1//2-1.4:1.0 RootHub为2-1,在RootHub 1号端口上级联了hub,并且使用级联hub的4号端口,1号配置,2号端口
[17237.016753] option 2-1.4:1.2: GSM modem (1-port) converter detected
[17237.026222] usb 2-1.4: GSM modem (1-port) converter now attached to ttyUSB2//2-1.4:1.0 RootHub为2-1,在RootHub 1号端口上级联了hub,并且使用级联hub的4号端口,1号配置,3号端口
[17237.042223] cdc_ether 2-1.4:1.3 usb0: register 'cdc_ether' at usb-sunxi-ehci-1.4, CDC Ethernet Device, 9e:08:f0:10:ff:04