Re: MFD device driver on top of UART/RS232

[Sascha Hauer <s.hauer@pengutronix.de>]

Hi Andrey,

+Cc NeilBrown <neil@brown.name>

On Mon, Nov 16, 2015 at 07:24:58PM +0300, Andrey Vostrikov wrote:
> Hi,
> 
> I have an embedded system with microcontroller connected via
> UART/RS232 port. This microcontroller implements several low-level
> functions that need to be exposed as device drivers in other
> subsystems (watchdog, LEDs, HWMON, firmware read/write).
> 
> I checked many drivers implemented in the kernel, searched through
> mail list archives and it looks like there are three different ways to
> solve this task:
> A) most of the devices that are connected using UART have user space
> program that configures and manages it (either directly or with help
> of dedicated line discipline, SLIP, SL-CAN, etc)
> B) serio - mostly used for input devices
> C) direct use of UART port taking control from serial_core.
> 
> The best match I have found so far is MFD driver for Atmel
> Microcontroller on iPaq h3xxx (drivers/mfd/ipaq-micro.c) that follows
> concept "C)"

There's also D) TTY slave device support: https://lkml.org/lkml/2015/3/18/40

Unfortunately this hasn't made it to mainline yet and it seems the
parties lost interest after some lengthy discussion of device tree phandles
vs. subnodes, but I think this is what you're looking for.

Sascha

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