From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751293AbdGQQkM (ORCPT ); Mon, 17 Jul 2017 12:40:12 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:52238 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751311AbdGQQkL (ORCPT ); Mon, 17 Jul 2017 12:40:11 -0400 Date: Mon, 17 Jul 2017 18:40:06 +0200 From: Greg KH To: Jiri Pirko Cc: linux-kernel@vger.kernel.org, davem@davemloft.net, mchehab@kernel.org, jikos@kernel.org Subject: Re: [patch 0/2] add actuators support Message-ID: <20170717164006.GB11246@kroah.com> References: <20170717161914.5043-1-jiri@resnulli.us> <20170717162838.GF9786@kroah.com> <20170717163458.GA1920@nanopsycho.orion> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170717163458.GA1920@nanopsycho.orion> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 17, 2017 at 06:34:58PM +0200, Jiri Pirko wrote: > Mon, Jul 17, 2017 at 06:28:38PM CEST, gregkh@linuxfoundation.org wrote: > >On Mon, Jul 17, 2017 at 06:19:12PM +0200, Jiri Pirko wrote: > >> From: Jiri Pirko > >> > >> I am owner of height adjustable desk and naturally, as it has an USB > >> interface, I need to controll it from my computer. Started to think > >> about what would be the best way, I realized that I need to introduce > >> a new driver class in kernel. The reason is a need to have one API > >> for all possible kinds of actuator devices (USB, I2C, gpio, etc). > > > >Why does this have to be a kernel driver at all? Your USB driver should > >really just be a simple userspace application (use libusb to have it > >work on all operating systems.) > > Yeah, I was thinking about it as well. To have some kind of single > purpose app like sispmctl (control of surge protector). But that would > limit you only for this specific device. And for multiple devices you > would have to have multiple apps. > > So it seems to me like a suitable solution to have this as a driver > class. For USB devices, especially ones as simple as this, we don't want them to have kernel drivers. It's just overkill. And never create a class if you only have one type of device, otherwise you don't know if you really have it properly defined or not. 3 is a good number to start with. sorry, greg k-h