From mboxrd@z Thu Jan  1 00:00:00 1970
From: arnd@arndb.de (Arnd Bergmann)
Date: Thu, 25 Aug 2011 23:38:08 +0200
Subject: kernel driver for rs232 serial peripheral
In-Reply-To: <4E56BE79.4030103@drewtech.com>
References: <4E56BE79.4030103@drewtech.com>
Message-ID: <4184628.BPS10NrKVa@wuerfel>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Thursday 25 August 2011 17:28:25 Joey Oravec wrote:
> We make a multi-function chip (rtc, gpio, nvram, etc) for embedded 
> applications that has an rs232 serial interface. My goal is to write an 
> MFD kernel driver that speaks serial to this device and implements 
> interfaces. Other busses like spi and i2c are pretty straightforward in 
> the kernel but serial feels a lot more complicated. To talk to this 
> device from the kernel it seems like I need to:
> 
> - Call tty_register_ldisc to create a line discipline
> - Call tty_register_driver and setup a driver
> - Require userspace to call setserial and change the line discipline
> 
> This might work, but the documentation implies that a line discipline is 
> for a protocol, not for connecting a device driver to a serial port. Is 
> there any kind of easier-to-use serial class similar to i2c or spi where 
> I can just setup a platform device/driver on a specific serial port? Am 
> I missing an easier solution?

I don't think you need to call tty_register_driver, if it's a standard
serial port, it should already work.
Also, I believe that there is a way to set the line discipline from
inside the kernel if you know what is connected. I forgot the details
but there should be a number of examples in the kernel source.

	Arnd