From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757396Ab2EBUqS (ORCPT ); Wed, 2 May 2012 16:46:18 -0400 Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:56508 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756646Ab2EBUqQ (ORCPT ); Wed, 2 May 2012 16:46:16 -0400 Date: Wed, 2 May 2012 21:49:01 +0100 From: Alan Cox To: Greg KH Cc: Preston Fick , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, preston.fick@silabs.com Subject: Re: [PATCH 3/3] usb: cp210x: Add ioctl for GPIO support Message-ID: <20120502214901.6b6e031c@pyramind.ukuu.org.uk> In-Reply-To: <20120502200356.GA25915@kroah.com> References: <1335845210-5147-1-git-send-email-preston.fick@silabs.com> <1335845210-5147-3-git-send-email-preston.fick@silabs.com> <20120502200356.GA25915@kroah.com> X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.8; 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 > Actually, why can't you use the GPIO subsystem for something like this? > Can't you export your device as both a usb-serial device and a gpio > device and have things work properly that way? You still need the ioctls even then in order to discover the gpio numbers, and having done that youi've got potential races with unload when you try and open them. You've also got permissions considerations and synchronization between gpio and data problems. It's not a good way to go. It might make sense in some platforms to expose them as both but its not a good general model. I'm currently favouring adding some 'additional control line' bits to termiox.