From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756039Ab0J0WUo (ORCPT ); Wed, 27 Oct 2010 18:20:44 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:39431 "EHLO www.etchedpixels.co.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751031Ab0J0WUm (ORCPT ); Wed, 27 Oct 2010 18:20:42 -0400 Date: Wed, 27 Oct 2010 23:19:48 +0100 From: Alan Cox To: Timur Tabi Cc: gregkh , lkml Subject: Re: Writing a console/tty driver -- how to use tty_port? Message-ID: <20101027231948.5e62dd09@lxorguk.ukuu.org.uk> In-Reply-To: <4CC893CD.7020701@freescale.com> References: <4CC893CD.7020701@freescale.com> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Face: 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 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 27 Oct 2010 16:04:13 -0500 Timur Tabi wrote: > Greg, > > Do you have an updated version of Tiny TTY that uses tty_port structures? I'm > trying to write a new TTY driver for a device that is not a UART, and I'm having > a hard time finding a good example. I suspect I need to understand the tty_port > structure, but I can't find any documentation for it. > > One specific problem I'm having is that I can't figure out how to get a > tty_struct pointer in my interrupt handler. The ISR gets called whenever there > is new input, and it needs to call tty_insert_flip_string(). But it appears > that it's possible to have my driver opened multiple times, each time creating a > new TTY. But since I can only have one interrupt handler, I don't know how to > determine which of the tty_structs to use. I figure tty_port is a way to > resolve this problem, but I don't know how to use it exactly. You only have one tty struct for the multiple opens. Basically tty_port - lifetime of hardware being loaded tty_struct - lifetime open/close (and a bit beyond for refs) So you can use tty_port_tty_get() which also knows about all the ghastly internal locking rules. Eventually the rx buffer should be moved to the tty_port which will make the world vastly saner. drivers/mmc/card/sdio_uart.c is in some ways the best example, it handles all the horrible cases including unloading of hardware v open races, its way more than you'd need but does illustrate it all. I've also got a draft tty_kfifo layer which is designed to be tty_port with kfifo queues as a helper. Remind me next week if it would be useful and I'll dig it back out. Alan