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1Emulator for DELL0501 UART attached backlight controller2--------------------------------------------------------3 4Dell All In One (AIO) models released after 2017 use a backlight controller5board 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 with13the backlight controller board attached.14 15This small emulator allows testing16the drivers/platform/x86/dell/dell-uart-backlight.c driver without access17to an actual Dell All In One.18 19This requires:201. A (desktop) PC with a 16550 UART on the motherboard and a standard DB921 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 converter24 with a DB9 connector plugged into the same desktop PC.254. A DSDT overlay for the desktop PC replacing the _HID of the 16550 UART26 ACPI Device() with "DELL0501" and adding a _CID of "PNP0501", see27 DSDT.patch for an example of the necessary DSDT changes.28 29With everything setup and the NULL modem cable connected between30the 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/ttyUSB037 38And then (re)load the dell-uart-backlight driver:39 40sudo rmmod dell-uart-backlight; sudo modprobe dell-uart-backlight dyndbg41 42After this check "dmesg" to see if the driver correctly received43the firmware version string from the emulator. If this works there44should be a /sys/class/backlight/dell_uart_backlight/ directory now45and writes to the brightness or bl_power files should be reflected46by matching output from the emulator.47