1Emulator for DELL0501 UART attached backlight controller 2-------------------------------------------------------- 3 4Dell All In One (AIO) models released after 2017 use a backlight controller 5board connected to an UART. 6 7In DSDT this uart port will be defined as: 8 9 Name (_HID, "DELL0501") 10 Name (_CID, EisaId ("PNP0501") 11 12With the DELL0501 indicating that we are dealing with an UART with 13the backlight controller board attached. 14 15This small emulator allows testing 16the drivers/platform/x86/dell/dell-uart-backlight.c driver without access 17to an actual Dell All In One. 18 19This requires: 201. A (desktop) PC with a 16550 UART on the motherboard and a standard DB9 21 connector connected to this UART. 222. A DB9 NULL modem cable. 233. A second DB9 serial port, this can e.g. be a USB to serial converter 24 with a DB9 connector plugged into the same desktop PC. 254. A DSDT overlay for the desktop PC replacing the _HID of the 16550 UART 26 ACPI Device() with "DELL0501" and adding a _CID of "PNP0501", see 27 DSDT.patch for an example of the necessary DSDT changes. 28 29With everything setup and the NULL modem cable connected between 30the 2 serial ports run: 31 32./dell-uart-backlight-emulator <path-to-/dev/tty*S#-for-second-port> 33 34For example when using an USB to serial converter for the second port: 35 36./dell-uart-backlight-emulator /dev/ttyUSB0 37 38And then (re)load the dell-uart-backlight driver: 39 40sudo rmmod dell-uart-backlight; sudo modprobe dell-uart-backlight dyndbg 41 42After this check "dmesg" to see if the driver correctly received 43the firmware version string from the emulator. If this works there 44should be a /sys/class/backlight/dell_uart_backlight/ directory now 45and writes to the brightness or bl_power files should be reflected 46by matching output from the emulator. 47