Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753448AbaJTKTQ (ORCPT ); Mon, 20 Oct 2014 06:19:16 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:33591 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752915AbaJTKTO (ORCPT ); Mon, 20 Oct 2014 06:19:14 -0400 MIME-Version: 1.0 In-Reply-To: References: <1413384491-23703-1-git-send-email-octavian.purdila@intel.com> <1413384491-23703-4-git-send-email-octavian.purdila@intel.com> Date: Mon, 20 Oct 2014 13:19:12 +0300 Message-ID: Subject: Re: [PATCH v8 3/4] gpiolib: add irq_not_threaded flag to gpio_chip From: Octavian Purdila To: Alexandre Courbot Cc: Greg Kroah-Hartman , Linus Walleij , Wolfram Sang , Samuel Ortiz , Lee Jones , Arnd Bergmann , Johan Hovold , Daniel Baluta , Laurentiu Palcu , "linux-usb@vger.kernel.org" , Linux Kernel Mailing List , "linux-gpio@vger.kernel.org" , "linux-i2c@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 On Mon, Oct 20, 2014 at 8:08 AM, Alexandre Courbot wrote: > > On Wed, Oct 15, 2014 at 11:48 PM, Octavian Purdila > wrote: > > Some GPIO chips (e.g. the DLN2 USB adapter) have blocking get/set > > operation but do not need a threaded irq handler. > > Sorry if you already explained this (I have been a little bit late > with the GPIO reviews recently), but does this optimization bring a > significant benefit that justifies adding another field in struct > gpio_chip? If so it would be nice to have it in the commit message. If > not, do we need this at all? Hi Alexandre, In the case DLN2 USB GPIO adapter the GPIO interrupt is generated in the completion routine of a receive URB, which means that we are in interrupt context. If a threaded irq is used, we would have to schedule work instead of running to interrupt handler directly which is unnecessary and adds latency. BTW, AFAIC Linus W already merged this patch in his next tree, I am keeping it in this series because it was not pulled in the mfd-next tree. Thanks, Tavi -- 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/