usb_linux.cpp - SHIFTPHONES/android_packages_modules_adb - Gitiles

 /*
  * Copyright (C) 2007 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.
  */

 #define TRACE_TAG TRACE_USB

 #include "sysdeps.h"

 #include <ctype.h>
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/usbdevice_fs.h>
 #include <linux/version.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/ioctl.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <unistd.h>
 #include <linux/usb/ch9.h>

 #include <base/file.h>
 #include <base/stringprintf.h>
 #include <base/strings.h>

 #include "adb.h"
 #include "transport.h"

 /* usb scan debugging is waaaay too verbose */
 #define DBGX(x...)

 ADB_MUTEX_DEFINE( usb_lock );

 struct usb_handle
 {
     usb_handle *prev;
     usb_handle *next;

     char fname[64];
     int desc;
     unsigned char ep_in;
     unsigned char ep_out;

     unsigned zero_mask;
     unsigned writeable;

     struct usbdevfs_urb urb_in;
     struct usbdevfs_urb urb_out;

     int urb_in_busy;
     int urb_out_busy;
     int dead;

     adb_cond_t notify;
     adb_mutex_t lock;

     // for garbage collecting disconnected devices
     int mark;

     // ID of thread currently in REAPURB
     pthread_t reaper_thread;
 };

 static usb_handle handle_list = {
     .prev = &handle_list,
     .next = &handle_list,
 };

 static int known_device(const char *dev_name)
 {
     usb_handle *usb;

     adb_mutex_lock(&usb_lock);
     for(usb = handle_list.next; usb != &handle_list; usb = usb->next){
         if(!strcmp(usb->fname, dev_name)) {
             // set mark flag to indicate this device is still alive
             usb->mark = 1;
             adb_mutex_unlock(&usb_lock);
             return 1;
         }
     }
     adb_mutex_unlock(&usb_lock);
     return 0;
 }

 static void kick_disconnected_devices()
 {
     usb_handle *usb;

     adb_mutex_lock(&usb_lock);
     // kick any devices in the device list that were not found in the device scan
     for(usb = handle_list.next; usb != &handle_list; usb = usb->next){
         if (usb->mark == 0) {
             usb_kick(usb);
         } else {
             usb->mark = 0;
         }
     }
     adb_mutex_unlock(&usb_lock);

 }

 static inline int badname(const char *name)
 {
     while(*name) {
         if(!isdigit(*name++)) return 1;
     }
     return 0;
 }

 static void find_usb_device(const char *base,
         void (*register_device_callback)
                 (const char *, const char *, unsigned char, unsigned char, int, int, unsigned))
 {
     char busname[32], devname[32];
     unsigned char local_ep_in, local_ep_out;
     DIR *busdir , *devdir ;
     struct dirent *de;
     int fd ;

     busdir = opendir(base);
     if(busdir == 0) return;

     while((de = readdir(busdir)) != 0) {
         if(badname(de->d_name)) continue;

         snprintf(busname, sizeof busname, "%s/%s", base, de->d_name);
         devdir = opendir(busname);
         if(devdir == 0) continue;

 //        DBGX("[ scanning %s ]\n", busname);
         while((de = readdir(devdir))) {
             unsigned char devdesc[4096];
             unsigned char* bufptr = devdesc;
             unsigned char* bufend;
             struct usb_device_descriptor* device;
             struct usb_config_descriptor* config;
             struct usb_interface_descriptor* interface;
             struct usb_endpoint_descriptor *ep1, *ep2;
             unsigned zero_mask = 0;
             unsigned vid, pid;
             size_t desclength;

             if(badname(de->d_name)) continue;
             snprintf(devname, sizeof devname, "%s/%s", busname, de->d_name);

             if(known_device(devname)) {
                 DBGX("skipping %s\n", devname);
                 continue;
             }

 //            DBGX("[ scanning %s ]\n", devname);
             if((fd = unix_open(devname, O_RDONLY | O_CLOEXEC)) < 0) {
                 continue;
             }

             desclength = unix_read(fd, devdesc, sizeof(devdesc));
             bufend = bufptr + desclength;

                 // should have device and configuration descriptors, and atleast two endpoints
             if (desclength < USB_DT_DEVICE_SIZE + USB_DT_CONFIG_SIZE) {
                 D("desclength %zu is too small\n", desclength);
                 unix_close(fd);
                 continue;
             }

             device = (struct usb_device_descriptor*)bufptr;
             bufptr += USB_DT_DEVICE_SIZE;

             if((device->bLength != USB_DT_DEVICE_SIZE) || (device->bDescriptorType != USB_DT_DEVICE)) {
                 unix_close(fd);
                 continue;
             }

             vid = device->idVendor;
             pid = device->idProduct;
             DBGX("[ %s is V:%04x P:%04x ]\n", devname, vid, pid);

                 // should have config descriptor next
             config = (struct usb_config_descriptor *)bufptr;
             bufptr += USB_DT_CONFIG_SIZE;
             if (config->bLength != USB_DT_CONFIG_SIZE || config->bDescriptorType != USB_DT_CONFIG) {
                 D("usb_config_descriptor not found\n");
                 unix_close(fd);
                 continue;
             }

                 // loop through all the descriptors and look for the ADB interface
             while (bufptr < bufend) {
                 unsigned char length = bufptr[0];
                 unsigned char type = bufptr[1];

                 if (type == USB_DT_INTERFACE) {
                     interface = (struct usb_interface_descriptor *)bufptr;
                     bufptr += length;

                     if (length != USB_DT_INTERFACE_SIZE) {
                         D("interface descriptor has wrong size\n");
                         break;
                     }

                     DBGX("bInterfaceClass: %d,  bInterfaceSubClass: %d,"
                          "bInterfaceProtocol: %d, bNumEndpoints: %d\n",
                          interface->bInterfaceClass, interface->bInterfaceSubClass,
                          interface->bInterfaceProtocol, interface->bNumEndpoints);

                     if (interface->bNumEndpoints == 2 &&
                             is_adb_interface(vid, pid, interface->bInterfaceClass,
                             interface->bInterfaceSubClass, interface->bInterfaceProtocol))  {

                         struct stat st;
                         char pathbuf[128];
                         char link[256];
                         char *devpath = NULL;

                         DBGX("looking for bulk endpoints\n");
                             // looks like ADB...
                         ep1 = (struct usb_endpoint_descriptor *)bufptr;
                         bufptr += USB_DT_ENDPOINT_SIZE;
                             // For USB 3.0 SuperSpeed devices, skip potential
                             // USB 3.0 SuperSpeed Endpoint Companion descriptor
                         if (bufptr+2 <= devdesc + desclength &&
                             bufptr[0] == USB_DT_SS_EP_COMP_SIZE &&
                             bufptr[1] == USB_DT_SS_ENDPOINT_COMP) {
                             bufptr += USB_DT_SS_EP_COMP_SIZE;
                         }
                         ep2 = (struct usb_endpoint_descriptor *)bufptr;
                         bufptr += USB_DT_ENDPOINT_SIZE;
                         if (bufptr+2 <= devdesc + desclength &&
                             bufptr[0] == USB_DT_SS_EP_COMP_SIZE &&
                             bufptr[1] == USB_DT_SS_ENDPOINT_COMP) {
                             bufptr += USB_DT_SS_EP_COMP_SIZE;
                         }

                         if (bufptr > devdesc + desclength ||
                             ep1->bLength != USB_DT_ENDPOINT_SIZE ||
                             ep1->bDescriptorType != USB_DT_ENDPOINT ||
                             ep2->bLength != USB_DT_ENDPOINT_SIZE ||
                             ep2->bDescriptorType != USB_DT_ENDPOINT) {
                             D("endpoints not found\n");
                             break;
                         }

                             // both endpoints should be bulk
                         if (ep1->bmAttributes != USB_ENDPOINT_XFER_BULK ||
                             ep2->bmAttributes != USB_ENDPOINT_XFER_BULK) {
                             D("bulk endpoints not found\n");
                             continue;
                         }
                             /* aproto 01 needs 0 termination */
                         if(interface->bInterfaceProtocol == 0x01) {
                             zero_mask = ep1->wMaxPacketSize - 1;
                         }

                             // we have a match.  now we just need to figure out which is in and which is out.
                         if (ep1->bEndpointAddress & USB_ENDPOINT_DIR_MASK) {
                             local_ep_in = ep1->bEndpointAddress;
                             local_ep_out = ep2->bEndpointAddress;
                         } else {
                             local_ep_in = ep2->bEndpointAddress;
                             local_ep_out = ep1->bEndpointAddress;
                         }

                             // Determine the device path
                         if (!fstat(fd, &st) && S_ISCHR(st.st_mode)) {
                             char *slash;
                             ssize_t link_len;
                             snprintf(pathbuf, sizeof(pathbuf), "/sys/dev/char/%d:%d",
                                      major(st.st_rdev), minor(st.st_rdev));
                             link_len = readlink(pathbuf, link, sizeof(link) - 1);
                             if (link_len > 0) {
                                 link[link_len] = '\0';
                                 slash = strrchr(link, '/');
                                 if (slash) {
                                     snprintf(pathbuf, sizeof(pathbuf),
                                              "usb:%s", slash + 1);
                                     devpath = pathbuf;
                                 }
                             }
                         }

                         register_device_callback(devname, devpath,
                                 local_ep_in, local_ep_out,
                                 interface->bInterfaceNumber, device->iSerialNumber, zero_mask);
                         break;
                     }
                 } else {
                     bufptr += length;
                 }
             } // end of while

             unix_close(fd);
         } // end of devdir while
         closedir(devdir);
     } //end of busdir while
     closedir(busdir);
 }

 static int usb_bulk_write(usb_handle *h, const void *data, int len)
 {
     struct usbdevfs_urb *urb = &h->urb_out;
     int res;
     struct timeval tv;
     struct timespec ts;

     memset(urb, 0, sizeof(*urb));
     urb->type = USBDEVFS_URB_TYPE_BULK;
     urb->endpoint = h->ep_out;
     urb->status = -1;
     urb->buffer = (void*) data;
     urb->buffer_length = len;

     D("++ write ++\n");

     adb_mutex_lock(&h->lock);
     if(h->dead) {
         res = -1;
         goto fail;
     }
     do {
         res = ioctl(h->desc, USBDEVFS_SUBMITURB, urb);
     } while((res < 0) && (errno == EINTR));

     if(res < 0) {
         goto fail;
     }

     res = -1;
     h->urb_out_busy = 1;
     for(;;) {
         /* time out after five seconds */
         gettimeofday(&tv, NULL);
         ts.tv_sec = tv.tv_sec + 5;
         ts.tv_nsec = tv.tv_usec * 1000L;
         res = pthread_cond_timedwait(&h->notify, &h->lock, &ts);
         if(res < 0 || h->dead) {
             break;
         }
         if(h->urb_out_busy == 0) {
             if(urb->status == 0) {
                 res = urb->actual_length;
             }
             break;
         }
     }
 fail:
     adb_mutex_unlock(&h->lock);
     D("-- write --\n");
     return res;
 }

 static int usb_bulk_read(usb_handle *h, void *data, int len)
 {
     struct usbdevfs_urb *urb = &h->urb_in;
     struct usbdevfs_urb *out = NULL;
     int res;

     D("++ usb_bulk_read ++\n");
     memset(urb, 0, sizeof(*urb));
     urb->type = USBDEVFS_URB_TYPE_BULK;
     urb->endpoint = h->ep_in;
     urb->status = -1;
     urb->buffer = data;
     urb->buffer_length = len;


     adb_mutex_lock(&h->lock);
     if(h->dead) {
         res = -1;
         goto fail;
     }
     do {
         res = ioctl(h->desc, USBDEVFS_SUBMITURB, urb);
     } while((res < 0) && (errno == EINTR));

     if(res < 0) {
         goto fail;
     }

     h->urb_in_busy = 1;
     for(;;) {
         D("[ reap urb - wait ]\n");
         h->reaper_thread = pthread_self();
         adb_mutex_unlock(&h->lock);
         res = ioctl(h->desc, USBDEVFS_REAPURB, &out);
         int saved_errno = errno;
         adb_mutex_lock(&h->lock);
         h->reaper_thread = 0;
         if(h->dead) {
             res = -1;
             break;
         }
         if(res < 0) {
             if(saved_errno == EINTR) {
                 continue;
             }
             D("[ reap urb - error ]\n");
             break;
         }
         D("[ urb @%p status = %d, actual = %d ]\n",
             out, out->status, out->actual_length);

         if(out == &h->urb_in) {
             D("[ reap urb - IN complete ]\n");
             h->urb_in_busy = 0;
             if(urb->status == 0) {
                 res = urb->actual_length;
             } else {
                 res = -1;
             }
             break;
         }
         if(out == &h->urb_out) {
             D("[ reap urb - OUT compelete ]\n");
             h->urb_out_busy = 0;
             adb_cond_broadcast(&h->notify);
         }
     }
 fail:
     adb_mutex_unlock(&h->lock);
     D("-- usb_bulk_read --\n");
     return res;
 }


 int usb_write(usb_handle *h, const void *_data, int len)
 {
     D("++ usb_write ++\n");

     unsigned char *data = (unsigned char*) _data;
     int n = usb_bulk_write(h, data, len);
     if(n != len) {
         D("ERROR: n = %d, errno = %d (%s)\n",
             n, errno, strerror(errno));
         return -1;
     }

     if(h->zero_mask && !(len & h->zero_mask)) {
             /* if we need 0-markers and our transfer
             ** is an even multiple of the packet size,
             ** then send the zero markers.
             */
         n = usb_bulk_write(h, _data, 0);
         return n;
     }

     D("-- usb_write --\n");
     return 0;
 }

 int usb_read(usb_handle *h, void *_data, int len)
 {
     unsigned char *data = (unsigned char*) _data;
     int n;

     D("++ usb_read ++\n");
     while(len > 0) {
         int xfer = len;

         D("[ usb read %d fd = %d], fname=%s\n", xfer, h->desc, h->fname);
         n = usb_bulk_read(h, data, xfer);
         D("[ usb read %d ] = %d, fname=%s\n", xfer, n, h->fname);
         if(n != xfer) {
             if((errno == ETIMEDOUT) && (h->desc != -1)) {
                 D("[ timeout ]\n");
                 if(n > 0){
                     data += n;
                     len -= n;
                 }
                 continue;
             }
             D("ERROR: n = %d, errno = %d (%s)\n",
                 n, errno, strerror(errno));
             return -1;
         }

         len -= xfer;
         data += xfer;
     }

     D("-- usb_read --\n");
     return 0;
 }

 void usb_kick(usb_handle *h)
 {
     D("[ kicking %p (fd = %d) ]\n", h, h->desc);
     adb_mutex_lock(&h->lock);
     if(h->dead == 0) {
         h->dead = 1;

         if (h->writeable) {
             /* HACK ALERT!
             ** Sometimes we get stuck in ioctl(USBDEVFS_REAPURB).
             ** This is a workaround for that problem.
             */
             if (h->reaper_thread) {
                 pthread_kill(h->reaper_thread, SIGALRM);
             }

             /* cancel any pending transactions
             ** these will quietly fail if the txns are not active,
             ** but this ensures that a reader blocked on REAPURB
             ** will get unblocked
             */
             ioctl(h->desc, USBDEVFS_DISCARDURB, &h->urb_in);
             ioctl(h->desc, USBDEVFS_DISCARDURB, &h->urb_out);
             h->urb_in.status = -ENODEV;
             h->urb_out.status = -ENODEV;
             h->urb_in_busy = 0;
             h->urb_out_busy = 0;
             adb_cond_broadcast(&h->notify);
         } else {
             unregister_usb_transport(h);
         }
     }
     adb_mutex_unlock(&h->lock);
 }

 int usb_close(usb_handle *h)
 {
     D("++ usb close ++\n");
     adb_mutex_lock(&usb_lock);
     h->next->prev = h->prev;
     h->prev->next = h->next;
     h->prev = 0;
     h->next = 0;

     unix_close(h->desc);
     D("-- usb closed %p (fd = %d) --\n", h, h->desc);
     adb_mutex_unlock(&usb_lock);

     free(h);
     return 0;
 }

 static void register_device(const char* dev_name, const char* dev_path,
                             unsigned char ep_in, unsigned char ep_out,
                             int interface, int serial_index,
                             unsigned zero_mask) {
     // Since Linux will not reassign the device ID (and dev_name) as long as the
     // device is open, we can add to the list here once we open it and remove
     // from the list when we're finally closed and everything will work out
     // fine.
     //
     // If we have a usb_handle on the list 'o handles with a matching name, we
     // have no further work to do.
     adb_mutex_lock(&usb_lock);
     for (usb_handle* usb = handle_list.next; usb != &handle_list; usb = usb->next) {
         if (!strcmp(usb->fname, dev_name)) {
             adb_mutex_unlock(&usb_lock);
             return;
         }
     }
     adb_mutex_unlock(&usb_lock);

     D("[ usb located new device %s (%d/%d/%d) ]\n", dev_name, ep_in, ep_out, interface);
     usb_handle* usb = reinterpret_cast<usb_handle*>(calloc(1, sizeof(usb_handle)));
     if (usb == nullptr) fatal("couldn't allocate usb_handle");
     strcpy(usb->fname, dev_name);
     usb->ep_in = ep_in;
     usb->ep_out = ep_out;
     usb->zero_mask = zero_mask;
     usb->writeable = 1;

     adb_cond_init(&usb->notify, 0);
     adb_mutex_init(&usb->lock, 0);
     // Initialize mark to 1 so we don't get garbage collected after the device
     // scan.
     usb->mark = 1;
     usb->reaper_thread = 0;

     usb->desc = unix_open(usb->fname, O_RDWR | O_CLOEXEC);
     if (usb->desc == -1) {
         // Opening RW failed, so see if we have RO access.
         usb->desc = unix_open(usb->fname, O_RDONLY | O_CLOEXEC);
         if (usb->desc == -1) {
             D("[ usb open %s failed: %s]\n", usb->fname, strerror(errno));
             free(usb);
             return;
         }
         usb->writeable = 0;
     }

     D("[ usb opened %s%s, fd=%d]\n", usb->fname,
       (usb->writeable ? "" : " (read-only)"), usb->desc);

     if (usb->writeable) {
         if (ioctl(usb->desc, USBDEVFS_CLAIMINTERFACE, &interface) != 0) {
             D("[ usb ioctl(%d, USBDEVFS_CLAIMINTERFACE) failed: %s]\n",
               usb->desc, strerror(errno));
             unix_close(usb->desc);
             free(usb);
             return;
         }
     }

     // Read the device's serial number.
     std::string serial_path = android::base::StringPrintf(
         "/sys/bus/usb/devices/%s/serial", dev_path + 4);
     std::string serial;
     if (!android::base::ReadFileToString(serial_path, &serial)) {
         D("[ usb read %s failed: %s ]\n", serial_path.c_str(), strerror(errno));
         // We don't actually want to treat an unknown serial as an error because
         // devices aren't able to communicate a serial number in early bringup.
         // http://b/20883914
         serial = "";
     }
     serial = android::base::Trim(serial);

     // Add to the end of the active handles.
     adb_mutex_lock(&usb_lock);
     usb->next = &handle_list;
     usb->prev = handle_list.prev;
     usb->prev->next = usb;
     usb->next->prev = usb;
     adb_mutex_unlock(&usb_lock);

     register_usb_transport(usb, serial.c_str(), dev_path, usb->writeable);
 }

 static void* device_poll_thread(void* unused) {
     D("Created device thread\n");
     while (true) {
         // TODO: Use inotify.
         find_usb_device("/dev/bus/usb", register_device);
         kick_disconnected_devices();
         sleep(1);
     }
     return nullptr;
 }

 static void sigalrm_handler(int signo) {
     // don't need to do anything here
 }

 void usb_init()
 {
     struct sigaction    actions;

     memset(&actions, 0, sizeof(actions));
     sigemptyset(&actions.sa_mask);
     actions.sa_flags = 0;
     actions.sa_handler = sigalrm_handler;
     sigaction(SIGALRM,& actions, NULL);

     if (!adb_thread_create(device_poll_thread, nullptr)) {
         fatal_errno("cannot create input thread");
     }
 }
	/*
	* Copyright (C) 2007 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.
	*/

	#define TRACE_TAG TRACE_USB

	#include "sysdeps.h"

	#include <ctype.h>
	#include <dirent.h>
	#include <errno.h>
	#include <fcntl.h>
	#include <linux/usbdevice_fs.h>
	#include <linux/version.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <sys/ioctl.h>
	#include <sys/time.h>
	#include <sys/types.h>
	#include <unistd.h>
	#include <linux/usb/ch9.h>

	#include <base/file.h>
	#include <base/stringprintf.h>
	#include <base/strings.h>

	#include "adb.h"
	#include "transport.h"

	/* usb scan debugging is waaaay too verbose */
	#define DBGX(x...)

	ADB_MUTEX_DEFINE( usb_lock );

	struct usb_handle
	{
	usb_handle *prev;
	usb_handle *next;

	char fname[64];
	int desc;
	unsigned char ep_in;
	unsigned char ep_out;

	unsigned zero_mask;
	unsigned writeable;

	struct usbdevfs_urb urb_in;
	struct usbdevfs_urb urb_out;

	int urb_in_busy;
	int urb_out_busy;
	int dead;

	adb_cond_t notify;
	adb_mutex_t lock;

	// for garbage collecting disconnected devices
	int mark;

	// ID of thread currently in REAPURB
	pthread_t reaper_thread;
	};

	static usb_handle handle_list = {
	.prev = &handle_list,
	.next = &handle_list,
	};

	static int known_device(const char *dev_name)
	{
	usb_handle *usb;

	adb_mutex_lock(&usb_lock);
	for(usb = handle_list.next; usb != &handle_list; usb = usb->next){
	if(!strcmp(usb->fname, dev_name)) {
	// set mark flag to indicate this device is still alive
	usb->mark = 1;
	adb_mutex_unlock(&usb_lock);
	return 1;
	}
	}
	adb_mutex_unlock(&usb_lock);
	return 0;
	}

	static void kick_disconnected_devices()
	{
	usb_handle *usb;

	adb_mutex_lock(&usb_lock);
	// kick any devices in the device list that were not found in the device scan
	for(usb = handle_list.next; usb != &handle_list; usb = usb->next){
	if (usb->mark == 0) {
	usb_kick(usb);
	} else {
	usb->mark = 0;
	}
	}
	adb_mutex_unlock(&usb_lock);

	}

	static inline int badname(const char *name)
	{
	while(*name) {
	if(!isdigit(*name++)) return 1;
	}
	return 0;
	}

	static void find_usb_device(const char *base,
	void (*register_device_callback)
	(const char , const char , unsigned char, unsigned char, int, int, unsigned))
	{
	char busname[32], devname[32];
	unsigned char local_ep_in, local_ep_out;
	DIR busdir , devdir ;
	struct dirent *de;
	int fd ;

	busdir = opendir(base);
	if(busdir == 0) return;

	while((de = readdir(busdir)) != 0) {
	if(badname(de->d_name)) continue;

	snprintf(busname, sizeof busname, "%s/%s", base, de->d_name);
	devdir = opendir(busname);
	if(devdir == 0) continue;

	// DBGX("[ scanning %s ]\n", busname);
	while((de = readdir(devdir))) {
	unsigned char devdesc[4096];
	unsigned char* bufptr = devdesc;
	unsigned char* bufend;
	struct usb_device_descriptor* device;
	struct usb_config_descriptor* config;
	struct usb_interface_descriptor* interface;
	struct usb_endpoint_descriptor ep1, ep2;
	unsigned zero_mask = 0;
	unsigned vid, pid;
	size_t desclength;

	if(badname(de->d_name)) continue;
	snprintf(devname, sizeof devname, "%s/%s", busname, de->d_name);

	if(known_device(devname)) {
	DBGX("skipping %s\n", devname);
	continue;
	}

	// DBGX("[ scanning %s ]\n", devname);
	if((fd = unix_open(devname, O_RDONLY \| O_CLOEXEC)) < 0) {
	continue;
	}

	desclength = unix_read(fd, devdesc, sizeof(devdesc));
	bufend = bufptr + desclength;

	// should have device and configuration descriptors, and atleast two endpoints
	if (desclength < USB_DT_DEVICE_SIZE + USB_DT_CONFIG_SIZE) {
	D("desclength %zu is too small\n", desclength);
	unix_close(fd);
	continue;
	}

	device = (struct usb_device_descriptor*)bufptr;
	bufptr += USB_DT_DEVICE_SIZE;

	if((device->bLength != USB_DT_DEVICE_SIZE) \|\| (device->bDescriptorType != USB_DT_DEVICE)) {
	unix_close(fd);
	continue;
	}

	vid = device->idVendor;
	pid = device->idProduct;
	DBGX("[ %s is V:%04x P:%04x ]\n", devname, vid, pid);

	// should have config descriptor next
	config = (struct usb_config_descriptor *)bufptr;
	bufptr += USB_DT_CONFIG_SIZE;
	if (config->bLength != USB_DT_CONFIG_SIZE \|\| config->bDescriptorType != USB_DT_CONFIG) {
	D("usb_config_descriptor not found\n");
	unix_close(fd);
	continue;
	}

	// loop through all the descriptors and look for the ADB interface
	while (bufptr < bufend) {
	unsigned char length = bufptr[0];
	unsigned char type = bufptr[1];

	if (type == USB_DT_INTERFACE) {
	interface = (struct usb_interface_descriptor *)bufptr;
	bufptr += length;

	if (length != USB_DT_INTERFACE_SIZE) {
	D("interface descriptor has wrong size\n");
	break;
	}

	DBGX("bInterfaceClass: %d, bInterfaceSubClass: %d,"
	"bInterfaceProtocol: %d, bNumEndpoints: %d\n",
	interface->bInterfaceClass, interface->bInterfaceSubClass,
	interface->bInterfaceProtocol, interface->bNumEndpoints);

	if (interface->bNumEndpoints == 2 &&
	is_adb_interface(vid, pid, interface->bInterfaceClass,
	interface->bInterfaceSubClass, interface->bInterfaceProtocol)) {

	struct stat st;
	char pathbuf[128];
	char link[256];
	char *devpath = NULL;

	DBGX("looking for bulk endpoints\n");
	// looks like ADB...
	ep1 = (struct usb_endpoint_descriptor *)bufptr;
	bufptr += USB_DT_ENDPOINT_SIZE;
	// For USB 3.0 SuperSpeed devices, skip potential
	// USB 3.0 SuperSpeed Endpoint Companion descriptor
	if (bufptr+2 <= devdesc + desclength &&
	bufptr[0] == USB_DT_SS_EP_COMP_SIZE &&
	bufptr[1] == USB_DT_SS_ENDPOINT_COMP) {
	bufptr += USB_DT_SS_EP_COMP_SIZE;
	}
	ep2 = (struct usb_endpoint_descriptor *)bufptr;
	bufptr += USB_DT_ENDPOINT_SIZE;
	if (bufptr+2 <= devdesc + desclength &&
	bufptr[0] == USB_DT_SS_EP_COMP_SIZE &&
	bufptr[1] == USB_DT_SS_ENDPOINT_COMP) {
	bufptr += USB_DT_SS_EP_COMP_SIZE;
	}

	if (bufptr > devdesc + desclength \|\|
	ep1->bLength != USB_DT_ENDPOINT_SIZE \|\|
	ep1->bDescriptorType != USB_DT_ENDPOINT \|\|
	ep2->bLength != USB_DT_ENDPOINT_SIZE \|\|
	ep2->bDescriptorType != USB_DT_ENDPOINT) {
	D("endpoints not found\n");
	break;
	}

	// both endpoints should be bulk
	if (ep1->bmAttributes != USB_ENDPOINT_XFER_BULK \|\|
	ep2->bmAttributes != USB_ENDPOINT_XFER_BULK) {
	D("bulk endpoints not found\n");
	continue;
	}
	/* aproto 01 needs 0 termination */
	if(interface->bInterfaceProtocol == 0x01) {
	zero_mask = ep1->wMaxPacketSize - 1;
	}

	// we have a match. now we just need to figure out which is in and which is out.
	if (ep1->bEndpointAddress & USB_ENDPOINT_DIR_MASK) {
	local_ep_in = ep1->bEndpointAddress;
	local_ep_out = ep2->bEndpointAddress;
	} else {
	local_ep_in = ep2->bEndpointAddress;
	local_ep_out = ep1->bEndpointAddress;
	}

	// Determine the device path
	if (!fstat(fd, &st) && S_ISCHR(st.st_mode)) {
	char *slash;
	ssize_t link_len;
	snprintf(pathbuf, sizeof(pathbuf), "/sys/dev/char/%d:%d",
	major(st.st_rdev), minor(st.st_rdev));
	link_len = readlink(pathbuf, link, sizeof(link) - 1);
	if (link_len > 0) {
	link[link_len] = '\0';
	slash = strrchr(link, '/');
	if (slash) {
	snprintf(pathbuf, sizeof(pathbuf),
	"usb:%s", slash + 1);
	devpath = pathbuf;
	}
	}
	}

	register_device_callback(devname, devpath,
	local_ep_in, local_ep_out,
	interface->bInterfaceNumber, device->iSerialNumber, zero_mask);
	break;
	}
	} else {
	bufptr += length;
	}
	} // end of while

	unix_close(fd);
	} // end of devdir while
	closedir(devdir);
	} //end of busdir while
	closedir(busdir);
	}

	static int usb_bulk_write(usb_handle h, const void data, int len)
	{
	struct usbdevfs_urb *urb = &h->urb_out;
	int res;
	struct timeval tv;
	struct timespec ts;

	memset(urb, 0, sizeof(*urb));
	urb->type = USBDEVFS_URB_TYPE_BULK;
	urb->endpoint = h->ep_out;
	urb->status = -1;
	urb->buffer = (void*) data;
	urb->buffer_length = len;

	D("++ write ++\n");

	adb_mutex_lock(&h->lock);
	if(h->dead) {
	res = -1;
	goto fail;
	}
	do {
	res = ioctl(h->desc, USBDEVFS_SUBMITURB, urb);
	} while((res < 0) && (errno == EINTR));

	if(res < 0) {
	goto fail;
	}

	res = -1;
	h->urb_out_busy = 1;
	for(;;) {
	/* time out after five seconds */
	gettimeofday(&tv, NULL);
	ts.tv_sec = tv.tv_sec + 5;
	ts.tv_nsec = tv.tv_usec * 1000L;
	res = pthread_cond_timedwait(&h->notify, &h->lock, &ts);
	if(res < 0 \|\| h->dead) {
	break;
	}
	if(h->urb_out_busy == 0) {
	if(urb->status == 0) {
	res = urb->actual_length;
	}
	break;
	}
	}
	fail:
	adb_mutex_unlock(&h->lock);
	D("-- write --\n");
	return res;
	}

	static int usb_bulk_read(usb_handle h, void data, int len)
	{
	struct usbdevfs_urb *urb = &h->urb_in;
	struct usbdevfs_urb *out = NULL;
	int res;

	D("++ usb_bulk_read ++\n");
	memset(urb, 0, sizeof(*urb));
	urb->type = USBDEVFS_URB_TYPE_BULK;
	urb->endpoint = h->ep_in;
	urb->status = -1;
	urb->buffer = data;
	urb->buffer_length = len;


	adb_mutex_lock(&h->lock);
	if(h->dead) {
	res = -1;
	goto fail;
	}
	do {
	res = ioctl(h->desc, USBDEVFS_SUBMITURB, urb);
	} while((res < 0) && (errno == EINTR));

	if(res < 0) {
	goto fail;
	}

	h->urb_in_busy = 1;
	for(;;) {
	D("[ reap urb - wait ]\n");
	h->reaper_thread = pthread_self();
	adb_mutex_unlock(&h->lock);
	res = ioctl(h->desc, USBDEVFS_REAPURB, &out);
	int saved_errno = errno;
	adb_mutex_lock(&h->lock);
	h->reaper_thread = 0;
	if(h->dead) {
	res = -1;
	break;
	}
	if(res < 0) {
	if(saved_errno == EINTR) {
	continue;
	}
	D("[ reap urb - error ]\n");
	break;
	}
	D("[ urb @%p status = %d, actual = %d ]\n",
	out, out->status, out->actual_length);

	if(out == &h->urb_in) {
	D("[ reap urb - IN complete ]\n");
	h->urb_in_busy = 0;
	if(urb->status == 0) {
	res = urb->actual_length;
	} else {
	res = -1;
	}
	break;
	}
	if(out == &h->urb_out) {
	D("[ reap urb - OUT compelete ]\n");
	h->urb_out_busy = 0;
	adb_cond_broadcast(&h->notify);
	}
	}
	fail:
	adb_mutex_unlock(&h->lock);
	D("-- usb_bulk_read --\n");
	return res;
	}


	int usb_write(usb_handle h, const void _data, int len)
	{
	D("++ usb_write ++\n");

	unsigned char data = (unsigned char) _data;
	int n = usb_bulk_write(h, data, len);
	if(n != len) {
	D("ERROR: n = %d, errno = %d (%s)\n",
	n, errno, strerror(errno));
	return -1;
	}

	if(h->zero_mask && !(len & h->zero_mask)) {
	/* if we need 0-markers and our transfer
	** is an even multiple of the packet size,
	** then send the zero markers.
	*/
	n = usb_bulk_write(h, _data, 0);
	return n;
	}

	D("-- usb_write --\n");
	return 0;
	}

	int usb_read(usb_handle h, void _data, int len)
	{
	unsigned char data = (unsigned char) _data;
	int n;

	D("++ usb_read ++\n");
	while(len > 0) {
	int xfer = len;

	D("[ usb read %d fd = %d], fname=%s\n", xfer, h->desc, h->fname);
	n = usb_bulk_read(h, data, xfer);
	D("[ usb read %d ] = %d, fname=%s\n", xfer, n, h->fname);
	if(n != xfer) {
	if((errno == ETIMEDOUT) && (h->desc != -1)) {
	D("[ timeout ]\n");
	if(n > 0){
	data += n;
	len -= n;
	}
	continue;
	}
	D("ERROR: n = %d, errno = %d (%s)\n",
	n, errno, strerror(errno));
	return -1;
	}

	len -= xfer;
	data += xfer;
	}

	D("-- usb_read --\n");
	return 0;
	}

	void usb_kick(usb_handle *h)
	{
	D("[ kicking %p (fd = %d) ]\n", h, h->desc);
	adb_mutex_lock(&h->lock);
	if(h->dead == 0) {
	h->dead = 1;

	if (h->writeable) {
	/* HACK ALERT!
	** Sometimes we get stuck in ioctl(USBDEVFS_REAPURB).
	** This is a workaround for that problem.
	*/
	if (h->reaper_thread) {
	pthread_kill(h->reaper_thread, SIGALRM);
	}

	/* cancel any pending transactions
	** these will quietly fail if the txns are not active,
	** but this ensures that a reader blocked on REAPURB
	** will get unblocked
	*/
	ioctl(h->desc, USBDEVFS_DISCARDURB, &h->urb_in);
	ioctl(h->desc, USBDEVFS_DISCARDURB, &h->urb_out);
	h->urb_in.status = -ENODEV;
	h->urb_out.status = -ENODEV;
	h->urb_in_busy = 0;
	h->urb_out_busy = 0;
	adb_cond_broadcast(&h->notify);
	} else {
	unregister_usb_transport(h);
	}
	}
	adb_mutex_unlock(&h->lock);
	}

	int usb_close(usb_handle *h)
	{
	D("++ usb close ++\n");
	adb_mutex_lock(&usb_lock);
	h->next->prev = h->prev;
	h->prev->next = h->next;
	h->prev = 0;
	h->next = 0;

	unix_close(h->desc);
	D("-- usb closed %p (fd = %d) --\n", h, h->desc);
	adb_mutex_unlock(&usb_lock);

	free(h);
	return 0;
	}

	static void register_device(const char* dev_name, const char* dev_path,
	unsigned char ep_in, unsigned char ep_out,
	int interface, int serial_index,
	unsigned zero_mask) {
	// Since Linux will not reassign the device ID (and dev_name) as long as the
	// device is open, we can add to the list here once we open it and remove
	// from the list when we're finally closed and everything will work out
	// fine.
	//
	// If we have a usb_handle on the list 'o handles with a matching name, we
	// have no further work to do.
	adb_mutex_lock(&usb_lock);
	for (usb_handle* usb = handle_list.next; usb != &handle_list; usb = usb->next) {
	if (!strcmp(usb->fname, dev_name)) {
	adb_mutex_unlock(&usb_lock);
	return;
	}
	}
	adb_mutex_unlock(&usb_lock);

	D("[ usb located new device %s (%d/%d/%d) ]\n", dev_name, ep_in, ep_out, interface);
	usb_handle* usb = reinterpret_cast<usb_handle*>(calloc(1, sizeof(usb_handle)));
	if (usb == nullptr) fatal("couldn't allocate usb_handle");
	strcpy(usb->fname, dev_name);
	usb->ep_in = ep_in;
	usb->ep_out = ep_out;
	usb->zero_mask = zero_mask;
	usb->writeable = 1;

	adb_cond_init(&usb->notify, 0);
	adb_mutex_init(&usb->lock, 0);
	// Initialize mark to 1 so we don't get garbage collected after the device
	// scan.
	usb->mark = 1;
	usb->reaper_thread = 0;

	usb->desc = unix_open(usb->fname, O_RDWR \| O_CLOEXEC);
	if (usb->desc == -1) {
	// Opening RW failed, so see if we have RO access.
	usb->desc = unix_open(usb->fname, O_RDONLY \| O_CLOEXEC);
	if (usb->desc == -1) {
	D("[ usb open %s failed: %s]\n", usb->fname, strerror(errno));
	free(usb);
	return;
	}
	usb->writeable = 0;
	}

	D("[ usb opened %s%s, fd=%d]\n", usb->fname,
	(usb->writeable ? "" : " (read-only)"), usb->desc);

	if (usb->writeable) {
	if (ioctl(usb->desc, USBDEVFS_CLAIMINTERFACE, &interface) != 0) {
	D("[ usb ioctl(%d, USBDEVFS_CLAIMINTERFACE) failed: %s]\n",
	usb->desc, strerror(errno));
	unix_close(usb->desc);
	free(usb);
	return;
	}
	}

	// Read the device's serial number.
	std::string serial_path = android::base::StringPrintf(
	"/sys/bus/usb/devices/%s/serial", dev_path + 4);
	std::string serial;
	if (!android::base::ReadFileToString(serial_path, &serial)) {
	D("[ usb read %s failed: %s ]\n", serial_path.c_str(), strerror(errno));
	// We don't actually want to treat an unknown serial as an error because
	// devices aren't able to communicate a serial number in early bringup.
	// http://b/20883914
	serial = "";
	}
	serial = android::base::Trim(serial);

	// Add to the end of the active handles.
	adb_mutex_lock(&usb_lock);
	usb->next = &handle_list;
	usb->prev = handle_list.prev;
	usb->prev->next = usb;
	usb->next->prev = usb;
	adb_mutex_unlock(&usb_lock);

	register_usb_transport(usb, serial.c_str(), dev_path, usb->writeable);
	}

	static void* device_poll_thread(void* unused) {
	D("Created device thread\n");
	while (true) {
	// TODO: Use inotify.
	find_usb_device("/dev/bus/usb", register_device);
	kick_disconnected_devices();
	sleep(1);
	}
	return nullptr;
	}

	static void sigalrm_handler(int signo) {
	// don't need to do anything here
	}

	void usb_init()
	{
	struct sigaction actions;

	memset(&actions, 0, sizeof(actions));
	sigemptyset(&actions.sa_mask);
	actions.sa_flags = 0;
	actions.sa_handler = sigalrm_handler;
	sigaction(SIGALRM,& actions, NULL);

	if (!adb_thread_create(device_poll_thread, nullptr)) {
	fatal_errno("cannot create input thread");
	}
	}