Kernel now 5.15.60 with RTLXXXU driver

August 13, 2022 — BarryK

I have had email communications with Muthukrishnan, Realtek wifi not working, but it does work on a different Linux distribution. He has investigated firmware, but narrowed the problem down to a missing kernel driver. This is part of one of his emails:

The issue appears to be that CONFIG_RTL8XXXU is not set in the kernel config setting. Since the firmware for my laptop is RTL8723BU, it appears to be not loading it at the time of booting.

An extract of the DOTconfig-5.15.16 is as follows:-

CONFIG_WLAN_VENDOR_REALTEK=y
CONFIG_RTL8180=m
CONFIG_RTL8187=m
CONFIG_RTL8187_LEDS=y
CONFIG_RTL_CARDS=m
CONFIG_RTL8192CE=m
CONFIG_RTL8192SE=m
CONFIG_RTL8192DE=m
CONFIG_RTL8723AE=m
CONFIG_RTL8723BE=m
CONFIG_RTL8188EE=m
CONFIG_RTL8192EE=m
CONFIG_RTL8821AE=m
CONFIG_RTL8192CU=m
CONFIG_RTLWIFI=m
CONFIG_RTLWIFI_PCI=m
CONFIG_RTLWIFI_USB=m
CONFIG_RTLWIFI_DEBUG=y
CONFIG_RTL8192C_COMMON=m
CONFIG_RTL8723_COMMON=m
CONFIG_RTLBTCOEXIST=m
# CONFIG_RTL8XXXU is not set

I have compiled the 5.15.60 kernel with CONFIG_8XXXU set. Here is the kernel documentation:

CONFIG_RTL8XXXU:
│
│ This is an alternative driver for various Realtek RTL8XXX
│ parts written to utilize the Linux mac80211 stack.
│ The driver is known to work with a number of RTL8723AU,
│ RL8188CU, RTL8188RU, RTL8191CU, and RTL8192CU devices
│
│ This driver is under development and has a limited feature
│ set. In particular it does not yet support 40MHz channels
│ and power management. However it should have a smaller
│ memory footprint than the vendor drivers and benefits
│ from the in kernel mac80211 stack.
│
│ It can coexist with drivers from drivers/staging/rtl8723au,
│ drivers/staging/rtl8192u, and drivers/net/wireless/rtlwifi,
│ but you will need to control which module you wish to load.

...it does not mention RTL8723BU. There is also this, which I did not enable:

CONFIG_RTL8XXXU_UNTESTED:
│
│ This option enables detection of Realtek 8723/8188/8191/8192 WiFi
│ USB devices which have not been tested directly by the driver
│ author or reported to be working by third parties.

Maybe I should have!

Tags: easy