From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sascha Hauer Subject: Re: MFD device driver on top of UART/RS232 Date: Tue, 17 Nov 2015 08:53:30 +0100 Message-ID: <20151117075330.GJ8526@pengutronix.de> References: <564A035A.3050108@gmail.com> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <564A035A.3050108@gmail.com> Sender: linux-embedded-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Andrey Vostrikov Cc: linux-serial@vger.kernel.org, linux-embedded@vger.kernel.org, NeilBrown Hi Andrey, +Cc NeilBrown 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 -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |