From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from PNZPR01CU001.outbound.protection.outlook.com (mail-centralindiaazolkn19011031.outbound.protection.outlook.com [52.103.68.31]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ABB683A0B29; Tue, 17 Mar 2026 09:53:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.103.68.31 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773741194; cv=fail; b=JX/1T+L+IVc2s7NNhO1b/wODggISGiVitccrzjGpbbLFlmRNRXE6JWZjbFOOphAdrCxgZn0TPRd4s9NKeIMVeBo11ThrKgGSA08ulAMXP+8okZzvd+L9Tf79+JcHZKSjdPxSvTNf1kD00S1TbEtA45k/+Nwcv3VOifZwAAdLt0M= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773741194; c=relaxed/simple; bh=Of/OEl5WRQoagPst4mU792hDdqKgqpRIh7Wb9F6yjpg=; h=Message-ID:Date:Subject:From:To:Cc:References:In-Reply-To: Content-Type:MIME-Version; b=Y7+b1S89djn1B8fFP/dCEFBGOVmqFKlNsZ35rEZpGdE1We3sTMZfztRkgVyHefptuVbTF8NHAAjBq1nF5/+lGZczZBlGiJJoHDub34ZrcFNuEswiE3KM3SH4HL6INjsN3iMZ4/QBFKxmrBCdfJUXHg87sl7lVhS/wbp3US6ma8Q= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=live.com; spf=pass smtp.mailfrom=live.com; dkim=pass (2048-bit key) header.d=live.com header.i=@live.com header.b=g1j8l6eZ; arc=fail smtp.client-ip=52.103.68.31 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=live.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=live.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=live.com header.i=@live.com header.b="g1j8l6eZ" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=yuPMJT4+Uos2OP7msX8tVZzVqotfYemK47D/vA3OGW9yaNF0WPrkndPuc7kAaReisdascCNhQQlLXLj4M79tjiLJmIXqJFwOyzV3Z41U8TfLVVvtrZF85AHwBkC0yAvVOAXMAABSdi74VEX1/j5qwnJF/fFYK3+SQ4Ma+sPfsgYxAQVvwL8wSBlNFbGX/VkR5EQzDLK4nM2bhnc2DyQpA8oX92XpiI443oVpBMgeL+u0SF45aXruKFxK9fiZokfmzrQavdWoeZ6jh5Z/EceYxwc1T7MiQ/FS+EaAUfkz4q5FnahCfbN3IQpwf2yAOjwb5uNv1nW4LaiAd0j5aj0fNQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=aFC9oLZBe/VERjik0ipWrkgUMjgkO4DzwhAk+9BvaFY=; b=gv8IPDGTgoz3C1rQ8cJBGKIlIBZLg78zvWPdLA0Ilv5xBnGEVKhfgRqEtyzMGC9O5fmYjSyd/dBHonlQJmoDJMy4WC8VAbemK48KUNmRgMQgT5YrmxbTEEU0DMVrKsTqaHlQathcRcjxhR1my4q6s5xKI3f7pMlPpnYk1+/nNXUf7lCxt3/5EvIxuEalQ7rAxXjiK8eiMWXpl8OQKPH3z0sx4F1tPRHoujH5zX8zIjLrSF0DgU5WGBpqZfUSHh82AriDEqnimB/AiZHWZQC+fEmkkszMwSMeINVlJE/nFi0oAK4qp+ewZxaQVoPVITOudyjRMM19R5hMHvaKF9X6gQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=none; dmarc=none; dkim=none; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=live.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=aFC9oLZBe/VERjik0ipWrkgUMjgkO4DzwhAk+9BvaFY=; b=g1j8l6eZzfW7V5XXCtodtDNzULfwC2LLA9vimxo7bSs9rIjgPPiu7YPvKUqIqEkaUVcPsOZ60EvPMsjAaZjvl/3NsZhEK0S5BHdgY0x2ZGTeUYgztZM/iIzwA9k///7lGw3Y9B3vNdKZrMplLFp5iDIc4EXmBPPbxFUjLbHMixXHfGndbvPBK0+29oqr+PAUK6AJBY+nCR1k62B0ApemlxHlvWFUTWgiefkVUpYTX1hv5ki6xopejBzmWKxiwiwMOAPFZCfUC0+A978vBmq/CDaWiIbJeHQ4KvR+GCJd+Ep0UiSVie9on5YeRletAg4nUrcLzexJMWS1GM5ebSNKBw== Received: from MAUPR01MB11546.INDPRD01.PROD.OUTLOOK.COM (2603:1096:a01:19c::18) by PN4PR01MB10999.INDPRD01.PROD.OUTLOOK.COM (2603:1096:c01:2f3::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9700.25; Tue, 17 Mar 2026 09:53:03 +0000 Received: from MAUPR01MB11546.INDPRD01.PROD.OUTLOOK.COM ([fe80::1fed:9b0b:69b:9295]) by MAUPR01MB11546.INDPRD01.PROD.OUTLOOK.COM ([fe80::1fed:9b0b:69b:9295%6]) with mapi id 15.20.9700.024; Tue, 17 Mar 2026 09:53:02 +0000 Message-ID: Date: Tue, 17 Mar 2026 15:22:58 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/2] efi: Save Brightness using EFI on Macs From: Aditya Garg To: Atharva Tiwari Cc: Lukas Wunner , Ard Biesheuvel , Hans de Goede , =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= , linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org References: <20260316153407.1781-1-atharvatiwarilinuxdev@gmail.com> <20260316153407.1781-2-atharvatiwarilinuxdev@gmail.com> <9FF2FDB9-17D4-4B01-A872-F26BFF74C5CC@live.com> Content-Language: en-US In-Reply-To: <9FF2FDB9-17D4-4B01-A872-F26BFF74C5CC@live.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: BMXPR01CA0073.INDPRD01.PROD.OUTLOOK.COM (2603:1096:b00:54::13) To MAUPR01MB11546.INDPRD01.PROD.OUTLOOK.COM (2603:1096:a01:19c::18) X-Microsoft-Original-Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MAUPR01MB11546:EE_|PN4PR01MB10999:EE_ X-MS-Office365-Filtering-Correlation-Id: 10ea6b8f-7a60-4e27-1360-08de840afae2 X-Microsoft-Antispam: BCL:0;ARA:14566002|19110799012|15080799012|8060799015|23021999003|5072599009|461199028|51005399006|25031999004|6090799003|10035399007|440099028|3412199025|11031999003|40105399003; X-Microsoft-Antispam-Message-Info: =?utf-8?B?dTdPMEltbmt6RkFOc2VpL1JSNzR4WDA2SmMwRDFiOFpDaDUxNXUyVzZLU3RS?= =?utf-8?B?eVZKeGU1eHlOR3BYNWFsK1lDQVBBcldiYTFsN3ppWHdGVnNYMUxsZUtEYXY2?= =?utf-8?B?RVhQbEt5aHU4ZzlhSFNhR3ZHaW4yWlZoTVRSRkFBR1N5NDh2NXF4RjVURUxS?= =?utf-8?B?aDhzVTVJMHlzdThRRmpjT0dxVE04ajg5NDU1NkZMbFJjMHhubVdvN0txT1Nm?= =?utf-8?B?NEMrMkZBeE83N3VrRGl0OHVlZjEyUGppRHhNRVRKd3VSS083UEN3VVpBNGxy?= =?utf-8?B?emczODFCbDlQYjc0R04xdDhHRDhveGJaa204R3RoT2wxY3ZvMWpIdEIrZzJB?= =?utf-8?B?clFrRzRrUzBuVFRjZUEvTGJoY09WeVdlMEVqMjVleEtQUUJZYSttOXE2TTEw?= =?utf-8?B?SDlxTStGNFdjL1NhcnJjVGJLL25WVzk3bVlwSDIzQi9kRDZpWUsxdmJxN25E?= =?utf-8?B?NXlKaHFyVndEZ1RLU2FkNStBdTJITlVSR0VoMlVQaEduVjVmNWxlb3hURERs?= =?utf-8?B?cXpHYmtlUmdxS2hLb0hXaTdrMjA5ZDl0Unlwcm9xd2xvSHNjdUFhOEQ5STlm?= =?utf-8?B?eHRCZ0FJVVp4VUwvVHZUbjBxaCsrVERQd2hoUlBGeTd1WjM4NmlXTDhON3FJ?= =?utf-8?B?WWx3dGZLaTZGOTJTd0tYak0zTGJiVnVIc2JKNkFSZ1FJek55TlFWTy9aL0s4?= =?utf-8?B?SnVzSHdYK1BFdi9mQWRYZGVJN3pPeHJlb3hRUlVnU1VveU02dExrR3BHdE1N?= =?utf-8?B?TGs4Vml3VkVKNjZobVIxd3FCajNSMG5QTTBhQU90VThrNGdVT29IdDZIZGxN?= =?utf-8?B?QmN3ZGIxamEyQnVuZmI1MEdOaEJYaXErZWg2N2V5Sk5mc2NmQlUySXBMemhF?= =?utf-8?B?R1BWdXY4L3dkRER3MTNGSW8vZjZkenhidEdBUEhZSFY3RlM2a2V4VXptSGRD?= =?utf-8?B?eDJaUnZCbjdzc3l5OHlIN1NyYXFpSkJGZVN5V1Q1YVk1dlRGRXFoRG9IcTEv?= =?utf-8?B?Y2xvWFdiRGRxd3FXdjgrQ3dvMG9TNXZPWVdPdDBCMjFYMkROalk0ekE3TVhS?= =?utf-8?B?YkZUL3o5cW13Uk9qVU9zY1VKYXBpM2orcFBIc3lLdGdyRVhKWk5hTXpKZ3No?= =?utf-8?B?NVdKSTR5aFgzU1VhdE9nc0d6ZDd4bHRPYTViSUs3THBYRktWb3NHdzdOQVlW?= =?utf-8?B?ZzZZSnYyM201UUZXVi95S1NIUmJaOWpsOU5zNk5DWlZIL2w5SDEzYTBnZVRa?= =?utf-8?B?VyszNU1wYk4rUjJ5QjBjMlJyaFJLeko2Q3B0NEt1STNtYXlScmZKb2piMGZK?= =?utf-8?B?eHlRbDFJbW5rblNFcFh1N3RUOTZxczRvTjArb0VWeGxBVXdWcnR0Y0d4ZFd3?= =?utf-8?B?TlMwblF1WElhNXc9PQ==?= X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?WDh4YnMrKzNqczBmeE5KK0xhUU1vWGN5dVNuVFErVVVGRzI3WXdhQ0p1OVJ5?= =?utf-8?B?emF2K3QwZTc5OHFBOWt6aVhpTjcrNUtQVU1nay9LR3dBa0xsbU9QdnRRVVYv?= =?utf-8?B?ZmV1bWJUT1MvdVZWemQ0R2ZpbHFVR240WTF5WGxYdURaTDZOdVFkUUhQQ0Vr?= =?utf-8?B?R2NXN2o1N1JvdUp6WFl6MjJ6YjdydmNVZDdmYXNLVDNDcHVRdXgzeHNZeXZ6?= =?utf-8?B?NHdsN1gwbTlyd3J1N1ZDTU1lK0NObnRoaWYrd3A2aW9vT1pZNU5yNEFVbnEy?= =?utf-8?B?OVZyakNsTEwrS2hVeTFhbDRKNHZyT2FPRTZCenRrcmJ4NGlnOWhwdlkrTTRv?= =?utf-8?B?ODZnWjJCNG1vdGtDNTZpMVZRdlJtMVRoTWU2RGVjaGtHczBpM2I1aENBOHpR?= =?utf-8?B?RnJMcW8rQnU5VzMrZzdNOE1OakU3My82RkRibUM4a0JURGQwOERxL0drSHN6?= =?utf-8?B?T1JndXIxSmtKekoxZFV3bURtNndHaE9RaWRQbnU1Zit6d3R4czlrcUg2bElN?= =?utf-8?B?YXRlV01iWEVjYzFnK2orVU5lQVN0MTJmSUN1WGpOTlVDMHNuRFg5TFFvYVl0?= =?utf-8?B?Yms2bUdVZXFGTStCNCsyWHFUeldtcEhXa1Z0b2E2SmNLZis4ZkpUcEhJUHBL?= =?utf-8?B?Z01XbS8rWitkZEJxYVRTUGNZbmk3WTBMeWt6eHZHcGgzWk9MVlN5ZW9ET0hU?= =?utf-8?B?ZnRvWmR6Ym41Ukd6dVJkbXRISDJEc3lOMHpTN1FsV0NBY0JRSzdvekg2RzN3?= =?utf-8?B?VmtZOVREOVJ1NmFjOHlIVFBmckJnN21FcU9Bb1JKZmRJamhwVlNFVnYwdGdF?= =?utf-8?B?SUs3dnBkNWcreU40cHVmY3JlbGE4OVEwUEFScXphSzRsOFhCekVETHdFN1Q0?= =?utf-8?B?U0h3V29SSlp6VE4vc1RpL1BFM3FVa2RORWFTdWZnUWI0Y05iMFB6b3ZzcTJu?= =?utf-8?B?TGMzSzd1R2pBdGR5c1NvSk1CZEo5eDNWbTJRUVBXZ1hyTlZvUVlIZ0tLKzV1?= =?utf-8?B?bXRNNHptbzdqNmlzUC8rRk1tSEs0ZG00VCtiMnlXWEdKa283cEhLUDV6U3Ev?= =?utf-8?B?cDJVMSs2cVBCZ3M2U05MWTEvdXJDVzMzak5jRXMyS3NhNFRVSElROGFOeVRZ?= =?utf-8?B?b2pnMmVrZWRTOVFDYzEvaFBCV09PSXlMM2hhc1duMVU5bVdrR2hlb3VNYjJW?= =?utf-8?B?V1VDbDRnZGVQdzhvR2EyWjRwU3FmNVFtck1zVDB4S3RkUDVyY1dTWlh5TjNr?= =?utf-8?B?ZnpUV1IrU3B0RkRIQ3dOVjFZeU50cXg0SG5DY3lrZE5wRnZNcEcxaTh5Vkly?= =?utf-8?B?eHJGbCs4UDFLNlBSZWsxaWZBZUpFNFdlcFkweVl6ejV5NWIzRGtvQ1FmZ21R?= =?utf-8?B?UEU3MXpNdDhDMDkxcThKdFdFOVJSTVRrdnJaSVNtZ3k5WC9Lc21IL0l6MVRZ?= =?utf-8?B?UXpiNEZmdXZ0RmVDdllEWDRZSlRDTUVzL1oyR040VEZ2dUdoR2ozSWZFV25M?= =?utf-8?B?WjM4Q2JhZ2VXWENTVTJ6aU5oSXBlTzJ6RU14V3RtekZ3Z0xzNWZUdVRMbTlC?= =?utf-8?B?cXQrSDNUSnJoM3R2RUdrcUtKeGZWRHdtbTZNQUhJTXBwTTZRRTlZVDRORmJD?= =?utf-8?B?V0p0K3R5Y2FOVVBtMlg0ZE9SVFFMWXFMM2ltOG9UTnVDMVJkZEZIc284Y0d3?= =?utf-8?B?ZkZMcGxGV3VzTDZWbzRtTWlKMlpybWx3eXdKU1R2bjJ3RktCRjlKejBpZWJM?= =?utf-8?B?VmxDNTRzNGoxVEVjK2NZa1k5QTdISjdJYWd1S3QwR0NISGF3cGhybXRPSkxo?= =?utf-8?B?cnQ2aUFyZmhnOGJXSGRyWk1NQ2pnWGl6TlZrbWRXVmZ5Y2I4MjNPZ29wZUs3?= =?utf-8?B?cnhMMDVld00vbWc4NzZ1a0FENVlONzhkVDJHRGdHZlpXWE9uL0gyL3p3S3d6?= =?utf-8?Q?hvA31RZ9n1BCcCVFSmzE4QQA95/3nMEy?= X-OriginatorOrg: sct-15-20-9412-4-msonline-outlook-63b91.templateTenant X-MS-Exchange-CrossTenant-Network-Message-Id: 10ea6b8f-7a60-4e27-1360-08de840afae2 X-MS-Exchange-CrossTenant-AuthSource: MAUPR01MB11546.INDPRD01.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Mar 2026 09:53:02.8957 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 84df9e7f-e9f6-40af-b435-aaaaaaaaaaaa X-MS-Exchange-CrossTenant-RMS-PersistedConsumerOrg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-Transport-CrossTenantHeadersStamped: PN4PR01MB10999 On 3/17/26 15:08, Aditya Garg wrote: > > >> On 16 Mar 2026, at 9:03 PM, Atharva Tiwari wrote: >> >> Currently when a Mac reboots, the brightness is not the same >> as the previous boot instead its the same as the last time the >> Mac booted macOS. >> >> We can fix this issue by saving the brightness level to the efivar >> backlight-level. >> >> (tested on iMac20,1) >> >> Suggested-by: Lukas Wunner >> Signed-off-by: Atharva Tiwari >> --- >> drivers/firmware/efi/Kconfig | 10 +++ >> drivers/firmware/efi/Makefile | 1 + >> drivers/firmware/efi/apple-brightness.c | 67 +++++++++++++++++++ >> .../linux/platform_data/apple-brightness.h | 20 ++++++ >> 4 files changed, 98 insertions(+) >> create mode 100644 drivers/firmware/efi/apple-brightness.c >> create mode 100644 include/linux/platform_data/apple-brightness.h > > I tested this patch on a MacBookPro16,1, which is a T2 Intel Mac, and the behaviour is very weird: > > 1. macOS will never respect any brightness set by Linux > 2. The Max brightness set by macOS is not the max brightness on Linux. I get these values on Linux: > > aditya@MacBook:~$ efivar -p -n '7c436110-ab2a-4bbb-a880-fe41995c9f82-backlight-level' > GUID: 7c436110-ab2a-4bbb-a880-fe41995c9f82 > Name: "backlight-level" > Attributes: > Non-Volatile > Boot Service Access > Runtime Service Access > Value: > 00000000 f1 02 |.. | > > aditya@MacBook:~$ cat /sys/class/backlight/gmux_backlight/brightness > 48238 > > 3. I set the Max brightness on Linux, and restarted. I get this: > > aditya@MacBook:~$ efivar -p -n '7c436110-ab2a-4bbb-a880-fe41995c9f82-backlight-level' > GUID: 7c436110-ab2a-4bbb-a880-fe41995c9f82 > Name: "backlight-level" > Attributes: > Non-Volatile > Boot Service Access > Runtime Service Access > Value: > 00000000 7a ff |z. | > > aditya@MacBook:~$ cat /sys/class/backlight/gmux_backlight/brightness > 65402 > > > 4. Finally, any attempt to reduce the brightness seems worthless as unless booted back to macOS, Linux always boots at max brightness, but the nvram variable is changed successfully: > > aditya@MacBook:~$ efivar -p -n '7c436110-ab2a-4bbb-a880-fe41995c9f82-backlight-level' > GUID: 7c436110-ab2a-4bbb-a880-fe41995c9f82 > Name: "backlight-level" > Attributes: > Non-Volatile > Boot Service Access > Runtime Service Access > Value: > 00000000 eb 41 |.A | > > aditya@MacBook:~$ cat /sys/class/backlight/gmux_backlight/brightness > 65402 > > > Overall, it’s very inconsistent. Also, I’ve noticed Windows doesn't mess around with efivars, rather stores the brightness locally and implements it on every boot, something which systemd should do on Linux. > > I've done another test as well: 1. I booted into macOS, and set a normal brightness, not too low, not too high. 2. I booted back to Linux. The brightness was consistent. These are the values: aditya@MacBook:~$ efivar -p -n '7c436110-ab2a-4bbb-a880-fe41995c9f82-backlight-level' GUID: 7c436110-ab2a-4bbb-a880-fe41995c9f82 Name: "backlight-level" Attributes: Non-Volatile Boot Service Access Runtime Service Access Value: 00000000 92 00 |.. | aditya@MacBook:~$ cat /sys/class/backlight/gmux_backlight/brightness 7792 This is the journalctl of that boot: https://termbin.com/p0vf 3. I slightly modified the brightness and restarted. Upon a restart, the brightness was max again: aditya@MacBook:~$ efivar -p -n '7c436110-ab2a-4bbb-a880-fe41995c9f82-backlight-level' GUID: 7c436110-ab2a-4bbb-a880-fe41995c9f82 Name: "backlight-level" Attributes: Non-Volatile Boot Service Access Runtime Service Access Value: 00000000 51 3a |Q: | aditya@MacBook:~$ cat /sys/class/backlight/gmux_backlight/brightness 63589 This is the journalctl of that boot: https://termbin.com/1z9r