From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751109AbdBSI0Z (ORCPT ); Sun, 19 Feb 2017 03:26:25 -0500 Received: from mail-wm0-f49.google.com ([74.125.82.49]:35121 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750816AbdBSI0X (ORCPT ); Sun, 19 Feb 2017 03:26:23 -0500 Date: Sun, 19 Feb 2017 08:26:18 +0000 From: Daniel Thompson To: Sudip Mukherjee Cc: Andrew Morton , Jingoo Han , Lee Jones , Bartlomiej Zolnierkiewicz , linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org Subject: Re: [PATCH] backlight: report error on failure Message-ID: <20170219082618.GB30444@wychelm.lan> References: <1484774630-4228-1-git-send-email-sudipm.mukherjee@gmail.com> <588FC682.9040503@gmail.com> <58A876EF.1040803@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <58A876EF.1040803@gmail.com> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Feb 18, 2017 at 04:31:43PM +0000, Sudip Mukherjee wrote: > On Monday 30 January 2017 11:04 PM, Sudip Mukherjee wrote: > > On Wednesday 18 January 2017 09:23 PM, Sudip Mukherjee wrote: > > > It is possible to update the backlight power and the brightness using > > > the sysfs and on writing it either returns the count or if the callback > > > function does not exist then returns the error code 'ENXIO'. > > > > > > We have a situation where the userspace client is writing to the sysfs > > > to update the power and since the callback function exists the client > > > receives the return value as count and considers the operation to be > > > successful. That is correct as the write to the sysfs was successful. > > > But there is no way to know if the actual operation was done or not. > > > > > > backlight_update_status() returns the error code if it fails. Pass that > > > to the userspace client who is trying to update the power so that the > > > client knows that the operation failed. > > > > > > Signed-off-by: Sudip Mukherjee > > > --- > > > > A gentle ping. > > Hi Andrew, > > Its more than one month now that this patch was submitted. Can you please > take it through your tree... else it will miss the merge window. Sorry you've been waiting so long for a review. Your "gentle ping" did result in a few minor tweaks to the maintainers but what it didn't (until today) provoke was review! To be honest, the ABI changes in the patch meant I wanted to check a few things first. However prompted by this mail I've just replied with the review I *should* have sent out a week ago [asking you rather than me to fill in some details about the likely effect of the ABI change ;-) ]. BTW, I did do some archeology eariler in the week and I think the kernel has been swallowing error codes here for >10 years, so I'm curious if this is a theoretic bug fix or are you aware of some tangible problem in userspace that results from it? Daniel.