usbmisc 自動產生usb device結點

環境：Upboard 6.0 + kernel 4.4.8

當usb driver是用usbmisc時，系統並不會長出對應的結點，
Driver=usb storage等看起來都正常，
所以看起來是必需手重加入：

system/core/init/devices.cpp

static void handle_generic_device_event(struct uevent *uevent)
{
    const char *base;
    const char *name;
    char devpath[DEVPATH_LEN] = {0};
    char **links = NULL;

    name = parse_device_name(uevent, 64);
    if (!name)
        return;

    struct ueventd_subsystem *subsystem =
            ueventd_subsystem_find_by_name(uevent->subsystem);

 //ERROR("TTest-%s, uevent->subsystem = %s\n", __FUNCTON__, uevent->subsystem);
 //ERROR("TTest-%s, uevent->device_name = %s\n", __FUNCTON__, uevent->device_name);

    if (subsystem) {
        const char *devname;

        switch (subsystem->devname_src) {
        case DEVNAME_UEVENT_DEVNAME:
            devname = uevent->device_name;
            break;

        case DEVNAME_UEVENT_DEVPATH:
            devname = name;
            break;

        default:
            ERROR("%s subsystem's devpath option is not set; ignoring event\n",
                    uevent->subsystem);
            return;
        }

        if (!assemble_devpath(devpath, subsystem->dirname, devname))
            return;
        mkdir_recursive_for_devpath(devpath);
    } else if (!strncmp(uevent->subsystem, "usb", 3)) {
         if (!strcmp(uevent->subsystem, "usb")) {
            if (uevent->device_name) {
                if (!assemble_devpath(devpath, "/dev", uevent->device_name))
                    return;
                mkdir_recursive_for_devpath(devpath);
             }
             else {
                 /* This imitates the file system that would be created
                  * if we were using devfs instead.
                  * Minors are broken up into groups of 128, starting at "001"
                  */
                 int bus_id = uevent->minor / 128 + 1;
                 int device_id = uevent->minor % 128 + 1;
                 /* build directories */
                 make_dir("/dev/bus", 0755);
                 make_dir("/dev/bus/usb", 0755);
                 snprintf(devpath, sizeof(devpath), "/dev/bus/usb/%03d", bus_id);
                 make_dir(devpath, 0755);
                 snprintf(devpath, sizeof(devpath), "/dev/bus/usb/%03d/%03d", bus_id, device_id);
             }
         } else {
   //add for usblp (thermal printer)
   if(!strncmp(uevent->subsystem, "usbmisc", 7))
   {
    if(!strncmp(uevent->device_name, "usb/lp", 6)){
     base = "/dev/usb/";
     make_dir(base, 0755);
    }
   }
   //end
   else
   /* ignore other USB events */
            return;
        }
     } else if (!strncmp(uevent->subsystem, "graphics", 8)) {
         base = "/dev/graphics/";
         make_dir(base, 0755);
     } else if (!strncmp(uevent->subsystem, "drm", 3)) {
         base = "/dev/dri/";
         make_dir(base, 0755);
     } else if (!strncmp(uevent->subsystem, "oncrpc", 6)) {
         base = "/dev/oncrpc/";
         make_dir(base, 0755);
     } else if (!strncmp(uevent->subsystem, "adsp", 4)) {
         base = "/dev/adsp/";
         make_dir(base, 0755);
     } else if (!strncmp(uevent->subsystem, "msm_camera", 10)) {
         base = "/dev/msm_camera/";
         make_dir(base, 0755);
     } else if(!strncmp(uevent->subsystem, "input", 5)) {
         base = "/dev/input/";
         make_dir(base, 0755);
     } else if(!strncmp(uevent->subsystem, "mtd", 3)) {
         base = "/dev/mtd/";
         make_dir(base, 0755);
     } else if(!strncmp(uevent->subsystem, "sound", 5)) {
         base = "/dev/snd/";
         make_dir(base, 0755);
     } else if(!strncmp(uevent->subsystem, "misc", 4) &&
                 !strncmp(name, "log_", 4)) {
         INFO("kernel logger is deprecated\n");
         base = "/dev/log/";
         make_dir(base, 0755);
         name += 4;
     } else
         base = "/dev/";
     links = get_character_device_symlinks(uevent);

     if (!devpath[0])
         snprintf(devpath, sizeof(devpath), "%s%s", base, name);

     handle_device(uevent->action, devpath, uevent->path, 0,
             uevent->major, uevent->minor, links);
}

ref : 程序園