am 4a280e3d: Merge "Don\'t use control requests to read device serial numbers."

* commit '4a280e3dbe002bb5419ec010f89cdc158244e435':
  Don't use control requests to read device serial numbers.

1 files changed, 103 insertions, 78 deletions

diff --git a/fastboot/usb_linux.c b/fastboot/usb_linux.c
index b7a9ca3..9153c8d 100644
--- a/fastboot/usb_linux.c
+++ b/fastboot/usb_linux.c
@@ -75,10 +75,18 @@ struct usb_handle
     unsigned char ep_out;
 };
 
+/* True if name isn't a valid name for a USB device in /sys/bus/usb/devices.
+ * Device names are made up of numbers, dots, and dashes, e.g., '7-1.5'.
+ * We reject interfaces (e.g., '7-1.5:1.0') and host controllers (e.g. 'usb1').
+ * The name must also start with a digit, to disallow '.' and '..'
+ */
 static inline int badname(const char *name)
 {
-    while(*name) {
-        if(!isdigit(*name++)) return 1;
+    if (!isdigit(*name))
+      return 1;
+    while(*++name) {
+        if(!isdigit(*name) && *name != '.' && *name != '-')
+            return 1;
     }
     return 0;
 }
@@ -95,7 +103,8 @@ static int check(void *_desc, int len, unsigned type, int size)
     return 0;
 }
 
-static int filter_usb_device(int fd, char *ptr, int len, int writable,
+static int filter_usb_device(int fd, char* sysfs_name,
+                             char *ptr, int len, int writable,
                              ifc_match_func callback,
                              int *ept_in_id, int *ept_out_id, int *ifc_id)
 {
@@ -131,69 +140,35 @@ static int filter_usb_device(int fd, char *ptr, int len, int writable,
     info.dev_protocol = dev->bDeviceProtocol;
     info.writable = writable;
 
-    // read device serial number (if there is one)
-    info.serial_number[0] = 0;
-    if (dev->iSerialNumber) {
-        struct usbdevfs_ctrltransfer  ctrl;
-        // Keep it short enough because some bootloaders are borked if the URB len is > 255
-        // 128 is too big by 1.
-        __u16 buffer[127];
-
-        memset(buffer, 0, sizeof(buffer));
-
-        ctrl.bRequestType = USB_DIR_IN|USB_TYPE_STANDARD|USB_RECIP_DEVICE;
-        ctrl.bRequest = USB_REQ_GET_DESCRIPTOR;
-        ctrl.wValue = (USB_DT_STRING << 8) | dev->iSerialNumber;
-        //language ID (en-us) for serial number string
-        ctrl.wIndex = 0x0409;
-        ctrl.wLength = sizeof(buffer);
-        ctrl.data = buffer;
-        ctrl.timeout = 50;
-
-        result = ioctl(fd, USBDEVFS_CONTROL, &ctrl);
-        if (result > 0) {
-            int i;
-            // skip first word, and copy the rest to the serial string, changing shorts to bytes.
-            result /= 2;
-            for (i = 1; i < result; i++)
-                info.serial_number[i - 1] = buffer[i];
-            info.serial_number[i - 1] = 0;
-        }
-    }
+    snprintf(info.device_path, sizeof(info.device_path), "usb:%s", sysfs_name);
 
-    /* We need to get a path that represents a particular port on a particular
-     * hub.  We are passed an fd that was obtained by opening an entry under
-     * /dev/bus/usb.  Unfortunately, the names of those entries change each
-     * time devices are plugged and unplugged.  So how to get a repeatable
-     * path?  udevadm provided the inspiration.  We can get the major and
-     * minor of the device file, read the symlink that can be found here:
-     *   /sys/dev/char/<major>:<minor>
-     * and then use the last element of that path.  As a concrete example, I
-     * have an Android device at /dev/bus/usb/001/027 so working with bash:
-     *   $ ls -l /dev/bus/usb/001/027
-     *   crw-rw-r-- 1 root plugdev 189, 26 Apr  9 11:03 /dev/bus/usb/001/027
-     *   $ ls -l /sys/dev/char/189:26
-     *   lrwxrwxrwx 1 root root 0 Apr  9 11:03 /sys/dev/char/189:26 ->
-     *           ../../devices/pci0000:00/0000:00:1a.7/usb1/1-4/1-4.2/1-4.2.3
-     * So our device_path would be 1-4.2.3 which says my device is connected
-     * to port 3 of a hub on port 2 of a hub on port 4 of bus 1 (per
-     * http://www.linux-usb.org/FAQ.html).
+    /* Read device serial number (if there is one).
+     * We read the serial number from sysfs, since it's faster and more
+     * reliable than issuing a control pipe read, and also won't
+     * cause problems for devices which don't like getting descriptor
+     * requests while they're in the middle of flashing.
      */
-    info.device_path[0] = '\0';
-    result = fstat(fd, &st);
-    if (!result && S_ISCHR(st.st_mode)) {
-        char cdev[128];
-        char link[256];
-        char *slash;
-        ssize_t link_len;
-        snprintf(cdev, sizeof(cdev), "/sys/dev/char/%d:%d",
-                 major(st.st_rdev), minor(st.st_rdev));
-        link_len = readlink(cdev, link, sizeof(link) - 1);
-        if (link_len > 0) {
-            link[link_len] = '\0';
-            slash = strrchr(link, '/');
-            if (slash)
-                snprintf(info.device_path, sizeof(info.device_path), "usb:%s", slash+1);
+    info.serial_number[0] = '\0';
+    if (dev->iSerialNumber) {
+        char path[80];
+        int fd;
+
+        snprintf(path, sizeof(path),
+                 "/sys/bus/usb/devices/%s/serial", sysfs_name);
+        path[sizeof(path) - 1] = '\0';
+
+        fd = open(path, O_RDONLY);
+        if (fd >= 0) {
+            int chars_read = read(fd, info.serial_number,
+                                  sizeof(info.serial_number) - 1);
+            close(fd);
+
+            if (chars_read <= 0)
+                info.serial_number[0] = '\0';
+            else if (info.serial_number[chars_read - 1] == '\n') {
+                // strip trailing newline
+                info.serial_number[chars_read - 1] = '\0';
+            }
         }
     }
 
@@ -241,14 +216,73 @@ static int filter_usb_device(int fd, char *ptr, int len, int writable,
     return -1;
 }
 
+static int read_sysfs_string(const char *sysfs_name, const char *sysfs_node,
+                             char* buf, int bufsize)
+{
+    char path[80];
+    int fd, n;
+
+    snprintf(path, sizeof(path),
+             "/sys/bus/usb/devices/%s/%s", sysfs_name, sysfs_node);
+    path[sizeof(path) - 1] = '\0';
+
+    fd = open(path, O_RDONLY);
+    if (fd < 0)
+        return -1;
+
+    n = read(fd, buf, bufsize - 1);
+    close(fd);
+
+    if (n < 0)
+        return -1;
+
+    buf[n] = '\0';
+
+    return n;
+}
+
+static int read_sysfs_number(const char *sysfs_name, const char *sysfs_node)
+{
+    char buf[16];
+    int value;
+
+    if (read_sysfs_string(sysfs_name, sysfs_node, buf, sizeof(buf)) < 0)
+        return -1;
+
+    if (sscanf(buf, "%d", &value) != 1)
+        return -1;
+
+    return value;
+}
+
+/* Given the name of a USB device in sysfs, get the name for the same
+ * device in devfs. Returns 0 for success, -1 for failure.
+ */
+static int convert_to_devfs_name(const char* sysfs_name,
+                                 char* devname, int devname_size)
+{
+    int busnum, devnum;
+
+    busnum = read_sysfs_number(sysfs_name, "busnum");
+    if (busnum < 0)
+        return -1;
+
+    devnum = read_sysfs_number(sysfs_name, "devnum");
+    if (devnum < 0)
+        return -1;
+
+    snprintf(devname, devname_size, "/dev/bus/usb/%03d/%03d", busnum, devnum);
+    return 0;
+}
+
 static usb_handle *find_usb_device(const char *base, ifc_match_func callback)
 {
     usb_handle *usb = 0;
-    char busname[64], devname[64];
+    char devname[64];
     char desc[1024];
     int n, in, out, ifc;
 
-    DIR *busdir, *devdir;
+    DIR *busdir;
     struct dirent *de;
     int fd;
     int writable;
@@ -259,15 +293,7 @@ static usb_handle *find_usb_device(const char *base, ifc_match_func callback)
     while((de = readdir(busdir)) && (usb == 0)) {
         if(badname(de->d_name)) continue;
 
-        sprintf(busname, "%s/%s", base, de->d_name);
-        devdir = opendir(busname);
-        if(devdir == 0) continue;
-
-//        DBG("[ scanning %s ]\n", busname);
-        while((de = readdir(devdir)) && (usb == 0)) {
-
-            if(badname(de->d_name)) continue;
-            sprintf(devname, "%s/%s", busname, de->d_name);
+        if(!convert_to_devfs_name(de->d_name, devname, sizeof(devname))) {
 
 //            DBG("[ scanning %s ]\n", devname);
             writable = 1;
@@ -282,7 +308,7 @@ static usb_handle *find_usb_device(const char *base, ifc_match_func callback)
 
             n = read(fd, desc, sizeof(desc));
 
-            if(filter_usb_device(fd, desc, n, writable, callback,
+            if(filter_usb_device(fd, de->d_name, desc, n, writable, callback,
                                  &in, &out, &ifc) == 0) {
                 usb = calloc(1, sizeof(usb_handle));
                 strcpy(usb->fname, devname);
@@ -301,7 +327,6 @@ static usb_handle *find_usb_device(const char *base, ifc_match_func callback)
                 close(fd);
             }
         }
-        closedir(devdir);
     }
     closedir(busdir);
 
@@ -431,5 +456,5 @@ int usb_close(usb_handle *h)
 
 usb_handle *usb_open(ifc_match_func callback)
 {
-    return find_usb_device("/dev/bus/usb", callback);
+    return find_usb_device("/sys/bus/usb/devices", callback);
 }