Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752162AbbHaEwI (ORCPT ); Mon, 31 Aug 2015 00:52:08 -0400 Received: from mail-oi0-f54.google.com ([209.85.218.54]:33668 "EHLO mail-oi0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750771AbbHaEwG (ORCPT ); Mon, 31 Aug 2015 00:52:06 -0400 MIME-Version: 1.0 In-Reply-To: <20150817193447.GS13472@usrtlx11787.corpusers.net> References: <1438048204-632-1-git-send-email-bjorn.andersson@sonymobile.com> <20150728210040.GE19610@dtor-ws> <20150810224109.GN6519@usrtlx11787.corpusers.net> <20150817193447.GS13472@usrtlx11787.corpusers.net> From: Alexandre Courbot Date: Mon, 31 Aug 2015 13:51:45 +0900 Message-ID: Subject: Re: [PATCH] input: gpio_keys: Don't report events on gpio failure To: Bjorn Andersson Cc: Linus Walleij , Dmitry Torokhov , "linux-input@vger.kernel.org" , "linux-kernel@vger.kernel.org" , John Stultz , "linux-gpio@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2995 Lines: 79 On Tue, Aug 18, 2015 at 4:34 AM, Bjorn Andersson wrote: > On Sun 16 Aug 23:59 PDT 2015, Alexandre Courbot wrote: > >> On Thu, Aug 13, 2015 at 10:06 PM, Linus Walleij >> wrote: >> > On Tue, Aug 11, 2015 at 12:41 AM, Bjorn Andersson >> > wrote: >> > >> >> But then the question first goes to Linus & co. >> >> >> >> gpio_chip->get() can return a negative value to indicate errors (and did >> >> so in this case), all parts of the API seems indicates that we can get >> >> an error (int vs bool). >> > >> > Ooops. >> > >> >> Should we change _gpiod_get_raw_value() to propagate this error? >> > >> > Yes for now. Can you patch it? :) >> > >> >> Or >> >> should we just ignore this issue and propagate an error as GPIO high >> >> reading? >> > >> > I don't know about the future. In some sense GPIOs are so smallish >> > resources that errorhandling every call to read/write them seem to >> > be a royal PITA. That is why I wanted to switch them to bool and get >> > rid of the problem, but now I also see that maybe that was not such a >> > smart idea, if errors do occur on the set/get_value path. >> >> Nowadays GPIOs may reside at the other end of an i2c bus, which means >> that even the simplest operation like reading a GPIO value can >> potentially fail. And it will probably not get better - wait until we >> implement GPIO-over-IP! :) >> > > Now that's progress! I can't wait ;) > >> So I'd say it makes sense to propagate errors returned by the driver's >> get() hook. This might contradict some of our earlier statements about >> simplifying the GPIO API, but is preferrable to having to make a >> decision as to which valid value to return if the driver fails... >> > > Sounds good. > > As we're patching up _gpiod_get_raw_value(), is the lack of a get() > implementation the same as a LOW or is that -ENOTSUPP? I don't see any reason why it should not be -ENOTSUPP if we start to manage errors properly. > >> It should then be made very clear in the documentation that the only >> positive values ever returned by the GPIO API will be 0 and 1 (we >> already have a clamping mechanism for that IIRC), and that negative >> values are propagated as-is. >> > > That makes sense. I'm however not able to find such clamping > macro/mechanism and it would be very beneficial here... > >> Linus, does that seem reasonable to you? Does anyone has the intention >> to address that one or should I add it to my short-term TODO list? > > If you have some input on above (is lack of get() an error) I can hack > up the patch. Excellent - since Linus gave his thumb up, I think you can go ahead. Looking forward to seeing this finally fixed. Thanks! Alex. -- 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/