Re: [Gta04-owner] [PATCH 0/4] UART slave device support - version 4

From: Andrey Vostrikov
Date: Fri Jan 15 2016 - 10:43:38 EST

Hi Nikolaus,

H. Nikolaus Schaller wrote:
And IMHO nobody has described that he/she needs a solution to model the*data* relationship
for devices connected behind a tty port.

I am not sure if my case fits *data* relationship or not in this case. Some time ago I asked about state of your patches.
In my case I have supervising microcontroller unit (MCU) that is connected to one of UARTs on SoC.

This MCU implements several functions that will be implemented as MFD driver:
- watchdog and system reset
- HWMON sensors
- Input/power button
- and similar low level functions

So in my case DTS binding looks like:

&uart3 {
mcu {
line-speed = <baud rate>;
watchdog {
timeout = <ms>;
...other params...
eeprom {
cell1 : cell@1 {
reg = <1 2>;
cell2 : cell@2 {
reg = <2 1>;
hwmon {
sensors-list = "voltage", "current", etc...;

This MCU receives commands and notifies MFD driver about events via UART protocol.
It looks like not really a slave though, more like a partnership from data flow point of view.

There is no user space code involved in this case as whole interactions are between drivers (just a kick to open /dev/ttyXXX using sys_open, as there is no way to start probe on uart_slave bus and assign line discipline).

Best regards,