Salvage Android Phone as Linux-Server (radio/wifi hardware broken)

Question

My device has hardware problems with radio/wifi. Hence it's not possible to use sim-card or wifi. That also makes it restart frequently. Now it's useless as a phone. So I am trying to turn it in a desk computer (mini-server linuxdeploy). Simple air-plane mode isn't enough to solve these reboots.

How I figure out its wifi/radio components were broken (tentative)

I have an OnePlus 6 enchilada.

It fails to detect sim-card and at the same time can't turn on wifi.

If I try to turn on wifi. In the second I click to turn it on it freezes and reboots.

I read multiple logcat logs to my best efforts. Also system crash dumps. All seams related to radio/wifi or tentatives to turn modem on.

One think that make its work again (sometimes): is by pressing exactly on the Qualcomm SDR845 RF transceiver (and also Qualcomm QDM3620, QDM3670, QDM3671 Diversity Receiver Modules) on the back.

Other people also faced similar issues and same temporary workarounds. They found it to be related with those components. Repairing the motherboard seams impossible. And support want a full motherboard replace which is impractical ($$$).

Deeper disable wifi/radio than simple air-plane mode

Is it possible to somehow to disable the WIFI/radio somehow deeper than simple air-plane mode? So I can use it as a desk mini-server. Installing linuxdeploy or any other software like that and use reverse tethering.

I tried many solutions around internet (including android.stackexchange) but none really works.

If someone could give me any tip or advice I would greatly appreciate!!

— iambr | Sources

Answer

I solved by myself so I'm sharing so it might be useful for others.

Deeper disable wifi/radio = recompile android Linux Kernel disabling wifi/radio drivers

First I tested the Lineage OS custom ROM for my device.

From that I got access to fully rebuild my Custom Lineage ROM. They have all source code for all supported devices including the source for the linux kernel for my mobile board (Qualcomm SDM845 Snapdragon 845 SoC).

When the kernel is built It should be decided if It will load driver modules (all SoC board component needs a driver) or have driver modules statically built in it. In either case the driver must be enabled during the kernel build. For configuring the linux kernel build a .config file is used.

After studying a lot more about linux kernel building. Found from here that QDSP6V5 from OnePlus 6 SoC SDM845 board was mandatory for mobile-data and WIFI when building the kernel.

Using Lineage OS docs and more research and 250 GB of source code and almost 12 hours of download (repo sync + brunch enchilada) I managed to build my custom Lineage OS 16.0 ROM after modifying the kernel .config fragment (enchilada_defconfig) from android\lineage\kernel\oneplus\sdm845\arch\arm64\configs\enchilada_defconfig.

Setting CONFIG_MSM_PIL_MSS_QDSP6V5 from y to n(NO).

Note: When building LOS I had to disable dashd since I couldn't find this file while extracting proprietary blobs. Comment it out on ~/android/lineage/vendor/oneplus/sdm845-common/Android.mk

#include $(CLEAR_VARS)

#LOCAL_MODULE := dashd

#LOCAL_MODULE_OWNER := oneplus

#LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT_SBIN)

#LOCAL_UNSTRIPPED_PATH := $(TARGET_ROOT_OUT_SBIN_UNSTRIPPED)

#LOCAL_SRC_FILES := proprietary/rootfs/sbin/dashd

#LOCAL_MODULE_TAGS := optional

#LOCAL_MODULE_CLASS := EXECUTABLES

#include $(BUILD_PREBUILT)

and deleting it from PRODUCT_PACKAGES += list on sdm845-common-vendor.mk on same folder.

Eureka!!

Wifi and Mobile not working at all.

No more reboots and internet working flawlessly from usb reverse tethering.

Hilariously solution is exactly like @Robert commented. I had to spent almost an year of exploration to find that by myself. `-)