如何利用rk3399调试RM500Q模块以便正常拨号上网呢

按照模块厂家提供的资料添加相关驱动以及配置不再赘述，主要是调试过程中系统层面有一个问题，首先看log：
D use-Rlog/RLOG-RIL RILU: find quectel module /sys/bus/u***/devices/8-1 idVendor=2c7c idProduct=0800
D SubscriptionController: [getPhoneId]- no sims, returning default phoneId=0
D use-Rlog/RLOG-RIL RILU: find /sys/bus/u***/devices/8-1:1.2/ttyUSB2
D use-Rlog/RLOG-RIL RILU: ttyAT = ttyUSB2
D use-Rlog/RLOG-RIL RILU: find /sys/bus/u***/devices/8-1:1.3/ttyUSB3
D use-Rlog/RLOG-RIL RILU: ttyPPP = ttyUSB3
D use-Rlog/RLOG-RIL RILU: find /sys/bus/u***/devices/8-1:1.0/ttyUSB0
D use-Rlog/RLOG-RIL RILU: ttyDM = ttyUSB0
D use-Rlog/RLOG-RIL RILU: find /sys/bus/u***/devices/8-1:1.1/ttyUSB1
D use-Rlog/RLOG-RIL RILU: ttyGPS = ttyUSB1
D use-Rlog/RLOG-RIL RILU: find /sys/bus/u***/devices/8-1:1.4/net/wwan0
D use-Rlog/RLOG-RIL RILU: u***net_adapter = wwan0
D use-Rlog/RLOG-RIL RILU: find /sys/bus/u***/devices/8-1:1.4/u***misc/cdc-wdm0
D use-Rlog/RLOG-RIL RILU: qmichannel = cdc-wdm0
E use-Rlog/RLOG-RIL RILU: Cannot access file:/dev/cdc-wdm0, errno = 2(No such file or directory)
E use-Rlog/RLOG-RIL RILU: patch for 'system/core/init/devices.cpp' is required!
......
D use-Rlog/RLOG-RIL MBIM: fail to open (/dev/cdc-wdm0), errno: 2 (No such file or directory)
D use-Rlog/RLOG-RIL SETUP_DATA_CA: ql_set_data_call_info pdp=1, ifname=wwan0, iptype=4, ipaddr=(null)
D use-Rlog/RLOG-RIL SETUP_DATA_CA: wwan0 IP Address: 0.0.0.0/0
D use-Rlog/RLOG-RIL SETUP_DATA_CA: get_local_ip: 0.0.0.0/0, cost 0 sec
E use-Rlog/RLOG-RIL SETUP_DATA_CA: Unable to setup PDP in requestSetupDataCall
很明显，找不到/dev/cdc-wdm0，确实没有注册，原因就在devices.cpp中注册/dev/cdc-wdm0的逻辑了，系统将cdc-wdm0注册成了u***misc设备，而该文件中缺少处理u***misc的逻辑，只需要稍作修改即可：
--- a/system/core/init/devices.cpp
+++ b/system/core/init/devices.cpp
@@ -679,7 +679,7 @@ static void handle_generic_device_event(struct uevent *uevent)
             return;
         mkdir_recursive_for_devpath(devpath);
     } else if (!strncmp(uevent->subsystem, "u***", 3)) {
-         if (!strcmp(uevent->subsystem, "u***")) {
+         if (!strcmp(uevent->subsystem, "u***")||!strcmp(uevent->subsystem, "u***misc")) {
             if (uevent->device_name) {
                 if (!assemble_devpath(devpath, "/dev", uevent->device_name))
                     return;
这样模块即可正常拨号上网。

原作者：空~。