1 Emulator for DELL0501 UART attached backlight controller
2 --------------------------------------------------------
3
4 Dell All In One (AIO) models released after 2017 use a backlight controller
5 board connected to an UART.
6
7 In DSDT this uart port will be defined as:
8
9 Name (_HID, "DELL0501")
10 Name (_CID, EisaId ("PNP0501")
11
12 With the DELL0501 indicating that we are dealing with an UART with
13 the backlight controller board attached.
14
15 This small emulator allows testing
16 the drivers/platform/x86/dell/dell-uart-backlight.c driver without access
17 to an actual Dell All In One.
18
19 This requires:
20 1. A (desktop) PC with a 16550 UART on the motherboard and a standard DB9
21 connector connected to this UART.
22 2. A DB9 NULL modem cable.
23 3. 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.
25 4. 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
29 With everything setup and the NULL modem cable connected between
30 the 2 serial ports run:
31
32 ./dell-uart-backlight-emulator <path-to-/dev/tty*S#-for-second-port>
33
34 For example when using an USB to serial converter for the second port:
35
36 ./dell-uart-backlight-emulator /dev/ttyUSB0
37
38 And then (re)load the dell-uart-backlight driver:
39
40 sudo rmmod dell-uart-backlight; sudo modprobe dell-uart-backlight dyndbg
41
42 After this check "dmesg" to see if the driver correctly received
43 the firmware version string from the emulator. If this works there
44 should be a /sys/class/backlight/dell_uart_backlight/ directory now
45 and writes to the brightness or bl_power files should be reflected
46 by matching output from the emulator.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.