From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:55972 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752988AbeDIT6o (ORCPT ); Mon, 9 Apr 2018 15:58:44 -0400 Subject: Patch "backlight: Report error on failure" has been added to the 4.9-stable tree To: sudipm.mukherjee@gmail.com, alexander.levin@microsoft.com, daniel.thompson@linaro.org, gregkh@linuxfoundation.org, lee.jones@linaro.org, sudip.mukherjee@codethink.co.uk Cc: , From: Date: Mon, 09 Apr 2018 21:57:37 +0200 Message-ID: <15233038576166@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled backlight: Report error on failure to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: backlight-report-error-on-failure.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From foo@baz Mon Apr 9 17:09:24 CEST 2018 From: Sudip Mukherjee Date: Wed, 17 May 2017 21:55:07 +0100 Subject: backlight: Report error on failure From: Sudip Mukherjee [ Upstream commit 7e715c2d9c27c23f3187454157c58cf292ed103e ] 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 Acked-by: Daniel Thompson Signed-off-by: Lee Jones Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/video/backlight/backlight.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -134,7 +134,7 @@ static ssize_t bl_power_store(struct dev { int rc; struct backlight_device *bd = to_backlight_device(dev); - unsigned long power; + unsigned long power, old_power; rc = kstrtoul(buf, 0, &power); if (rc) @@ -145,10 +145,16 @@ static ssize_t bl_power_store(struct dev if (bd->ops) { pr_debug("set power to %lu\n", power); if (bd->props.power != power) { + old_power = bd->props.power; bd->props.power = power; - backlight_update_status(bd); + rc = backlight_update_status(bd); + if (rc) + bd->props.power = old_power; + else + rc = count; + } else { + rc = count; } - rc = count; } mutex_unlock(&bd->ops_lock); @@ -176,8 +182,7 @@ int backlight_device_set_brightness(stru else { pr_debug("set brightness to %lu\n", brightness); bd->props.brightness = brightness; - backlight_update_status(bd); - rc = 0; + rc = backlight_update_status(bd); } } mutex_unlock(&bd->ops_lock); Patches currently in stable-queue which might be from sudipm.mukherjee@gmail.com are queue-4.9/backlight-report-error-on-failure.patch