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x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=microsoft.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935180AbeCSVCo (ORCPT ); Mon, 19 Mar 2018 17:02:44 -0400 Received: from mail-dm3nam03on0119.outbound.protection.outlook.com ([104.47.41.119]:22560 "EHLO NAM03-DM3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965224AbeCSQCs (ORCPT ); Mon, 19 Mar 2018 12:02:48 -0400 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Sudip Mukherjee , Sudip Mukherjee , Lee Jones , Sasha Levin Subject: [PATCH AUTOSEL for 4.9 159/281] backlight: Report error on failure Thread-Topic: [PATCH AUTOSEL for 4.9 159/281] backlight: Report error on failure Thread-Index: AQHTv5t6o1e4yVJlL02/Wbb6ZoVlxg== Date: Mon, 19 Mar 2018 16:01:01 +0000 Message-ID: <20180319155742.13731-159-alexander.levin@microsoft.com> References: <20180319155742.13731-1-alexander.levin@microsoft.com> In-Reply-To: <20180319155742.13731-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;DM5PR2101MB1062;7:+jraJQqPSvKyvrOfRrHn85SxBuJe6C4p+XeJ5i1XL8hDN4UI0GGrbC9hn8dEigH2WmKybwAfDWRlAxjjCsIX/3BbqSOU1eeYe5K77xPhoFLGqXsv2xDrVcdeud7rz/oAuAO4DoYYf//ht8ctl7Zyp2fe3VJ/36pTerMj1LOJqqQzCS3uMig2OUsKsiq8t4g9QLEFcNbCqny53AIFKQYAO5lsYfVKbXxuSTtQ3U8aBChky35vkO1ERnAPjxsH5kAT;20:Tpqr+AePsGyy1Z0SgehbjpdCoFo/Cse9bnkKRRva+u++4YVvVE0/cASSq/8EJq6OmBxAYIfBTa2JRrJWmvw+XEiXipxxp5NN/EPjengl2S6JVwijhQ5OFmdQLdW6Nkq30dpNKYAIvWT0hF+y9qXhWCdWLgcOijh95HEIwJfJcPM= x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: edadae51-5c2d-4bfc-bfd2-08d58db2d737 x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7193020);SRVR:DM5PR2101MB1062; 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x-microsoft-antispam-message-info: Jd0dztacVFX1VqgY0In93Kpb1maEfFLiUPIUQsq74hZ68Brsi6le++Q3xS9Q/8ZDBEazNbIhnSt7vhcCD+FSqnefdPrZYlDGyuE9Yojev8jLPwXtmiTC58bNx79vU2znX1Osg5svQH3O/BtiMEau/DWriCJKlNg1xmzU6rUaWGriRH7+BYZFXKajZRrviid1m9fC7MybYuDJtxF7rloMJjG/4mBgekwO1dN+Clpyl6LMeSFOVqbChdb+m7dXU/j893IlEwLkVENuWNgYKKIIHbM2k0BKiVmbT4Wav9L3WkRkwTfwP7oQ8wYXgEsj62TnWPW4JKT3563PwgVdzMbCeA== spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: edadae51-5c2d-4bfc-bfd2-08d58db2d737 X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Mar 2018 16:01:01.9211 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB1062 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 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 --- drivers/video/backlight/backlight.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/= backlight.c index 288318ad21dd..8049e7656daa 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -134,7 +134,7 @@ static ssize_t bl_power_store(struct device *dev, struc= t device_attribute *attr, { int rc; struct backlight_device *bd =3D to_backlight_device(dev); - unsigned long power; + unsigned long power, old_power; =20 rc =3D kstrtoul(buf, 0, &power); if (rc) @@ -145,10 +145,16 @@ static ssize_t bl_power_store(struct device *dev, str= uct device_attribute *attr, if (bd->ops) { pr_debug("set power to %lu\n", power); if (bd->props.power !=3D power) { + old_power =3D bd->props.power; bd->props.power =3D power; - backlight_update_status(bd); + rc =3D backlight_update_status(bd); + if (rc) + bd->props.power =3D old_power; + else + rc =3D count; + } else { + rc =3D count; } - rc =3D count; } mutex_unlock(&bd->ops_lock); =20 @@ -176,8 +182,7 @@ int backlight_device_set_brightness(struct backlight_de= vice *bd, else { pr_debug("set brightness to %lu\n", brightness); bd->props.brightness =3D brightness; - backlight_update_status(bd); - rc =3D 0; + rc =3D backlight_update_status(bd); } } mutex_unlock(&bd->ops_lock); --=20 2.14.1