My desired options
I'm building AOSP x86 image from source, i see that after flashing the built oreo image to the target system, 4G (recommended) option shown in above image is not visible in the Preferred network type drop down list.
I have set ro.telephony.default_network=9 in device.mk as given below. This ro.telephony.default_network=9 is also reflected under build.prop of the target system.
PRODUCT_PROPERTY_OVERRIDES :=
ro.ril.hsxpa=1
ro.ril.gprsclass=10
keyguard.no_require_sim=true
ro.com.android.dataroaming=true
media.sf.hwaccel=1
media.sf.omx-plugin=libffmpeg_omx.so
media.sf.extractor-plugin=libffmpeg_extractor.so
rild.libpath=/vendor/lib64/librapid-ril-core.so
ro.telephony.default_network=9
I can see 4G (recommended) selected by default in Preferred network type, but if i click on Preferred network type menu and go inside i see only 3G and 2G Radio buttons. 4G (recommended) is missing in the drop down menu.
Once i select one of the 3G or 2G Radio button, there is no way i can switch back to 4G (recommended) which was selected by default by the OS.
NOTE: i'm successfully able to get 4G download speeds when 4G( recommended) selected by default in Preferred network type. Changing to 3G and 2G will successfully get respective speeds and able to see corresponding network type indicator icon in status bar. So functionally Internet data connectivity is working fine in all 3 modes (4G, 3G and 2G).
How to modify source files to make the 4G (recommended) radio button visible under Preferred network type as indicated in above attached image?
I'm not able to enter engineering mode by dialing *#*#4636#*#* (any answers to enable this also grateful)
Reference: http://paldan.altervista.org/lte-in-aosp-preferred-network-settings/
To enable 4g(recommended) radio under Preferred Network Type menu, you must set config_enabled_lte to true in packages/services/Telephony/res/values/config.xml