Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751055AbbFBUL7 (ORCPT ); Tue, 2 Jun 2015 16:11:59 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:42971 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926AbbFBULt (ORCPT ); Tue, 2 Jun 2015 16:11:49 -0400 Date: Tue, 2 Jun 2015 22:11:43 +0200 From: Pavel Machek To: "Dr. H. Nikolaus Schaller" Cc: Kishon Vijay Abraham I , NeilBrown , Tony Lindgren , LKML , NeilBrown , linux-omap , List for communicating with real GTA04 owners Subject: Re: [Gta04-owner] [PATCH 5/6] phy: twl4030-usb: add support for reading resistor on ID pin. Message-ID: <20150602201143.GA26412@amd> References: <20150416075945.23307.24424.stgit@notabene.brown> <20150416080304.23307.41913.stgit@notabene.brown> <556C5FF4.3050603@ti.com> <20150602073731.26edbd3b@notabene.brown> <556DB481.3080906@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2016 Lines: 58 On Tue 2015-06-02 16:06:47, Dr. H. Nikolaus Schaller wrote: > Hi, > > Am 02.06.2015 um 15:49 schrieb Kishon Vijay Abraham I : > > > Hi, > > > > On Tuesday 02 June 2015 03:07 AM, NeilBrown wrote: > >> On Mon, 1 Jun 2015 19:06:52 +0530 Kishon Vijay Abraham I > >> wrote: > >> > >>> Hi, > >>> > >>> On Thursday 16 April 2015 01:33 PM, NeilBrown wrote: > >>>> From: NeilBrown > >>>> > >>>> The twl4030 phy can measure, with low precision, the > >>>> resistance-to-ground of the ID pin. > >>>> > >>>> Add a function to read the value, and export the result > >>>> via sysfs. > >>> > >>> Little sceptical about adding new sysfs entries. Do you have a good reason to > >>> add this? > >> > >> The hardware can report the value, so why not present it to user-space? > >> > >> I originally used this with a udev rule which would configure the maximum > >> current based on the resistance measure - to work with the particular charger > >> hardware I have. > >> > >> More recent patches try to do all of the max-current configuration in the > >> kernel, so I could live without exporting the value via sysfs if that is a > >> show-stopper. > >> > >> I can't see where the scepticism comes from though. It is a well defined > >> and cleary documented feature of the hardware. Why not expose it? Is it well defined enough that it will work on other chargers, too? > > ABI can never be removed or modified later. So should be really careful before adding it. > > Is /sys considered ABI? Yes. > User space developers are always reminded not to rely on /sys nodes. No. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/