From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f53.google.com (mail-pj1-f53.google.com [209.85.216.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C4D873A16B5 for ; Mon, 16 Mar 2026 15:34:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773675266; cv=none; b=fc2hqdW2SFoaD69skALA0+7H8hMUvZRAhY0MehRyMqxAOidj3dZO+dgoXwud8mlLKCvHnAYWHCjoVcbRCCshqEKYdQDwlfUaFTuc7+iS1TOUC7b+DJpUWmbieARndR5fyshN5glE1fLwpbjJeQHaZPF6jHgKjcOCwwuhRM8jpms= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773675266; c=relaxed/simple; bh=LLhiZ5FX8IIzUP55FXN9kMQNcPa8k1lZx7Q++ivYoEc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YJ6AlLUl3Rclw5JcckB07aig2nV1KUsjibFuhX49DWwuyq5+62oQQqogPH75jVdim2eFJfx/UW6BJOuDxwgnX83A2Az1+UtzoMZ2UOSSAV0/zeUqdniOb5J3Vf5nVGr72ktwJvLwxDkmfjfj5A5fHgT7B+o4zZsJBk2eLElhph0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Qpj94jU+; arc=none smtp.client-ip=209.85.216.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Qpj94jU+" Received: by mail-pj1-f53.google.com with SMTP id 98e67ed59e1d1-35ba749f441so592018a91.1 for ; Mon, 16 Mar 2026 08:34:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1773675264; x=1774280064; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=SjMa+jqjA5+TcVEkQU5jdnLuBqhO1REK2DuRHZyX1uY=; b=Qpj94jU+u9DOtwfmnRBnUc16yq/+cX0tNd+r1g4WZdp51voI/H4r+0DEPard+ui+2N xKZlgJz3QCRVct/VxZ3D4Z/Jxcj64eBjey74qWk+n6V/duZ5VoxbNrN8+85Mhi16H9Os /+hIDGQ1u0RJ8x6TCjKonp2uoIsa8ODSkNmkHIM9O2BH9FdkwfbL2eMZIXRpQRsOr9jJ D4d42iIIU5jHsf9wSkJm0OjqO0ZwwLJyqLf0MytBub4kW8pbq0OhGHFHFPTXXh3xkixZ 8IKHe7hXHwWx7ty71G/x4/m4AmmJfMQGIDX2zjxghAFBNgnPiqBbZtMD7UuBmOSRyeyv 0HbA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773675264; x=1774280064; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=SjMa+jqjA5+TcVEkQU5jdnLuBqhO1REK2DuRHZyX1uY=; b=LMVo01qE687skRTJqcHKHLvUF6WoQ9oHDtuE9uDgtgmMi/UBOCSNlpn+9ejx44mfqj 3VBxJkexRoFWkgWcSoIxtU6w65DIe3cWagkAIR2wgrcdruJrzVl4wV8XHmpX7+oZmefO 0NYO+pleQS3y9ezJTMSX5csfsJNVo2JkyUqstd3d3dTk/0gzHGRqlnneXLlGLG/m5pWK mlJyalhP0/eXtIKYAK2CQr/DoItQGIu29iRRnaNno3NfJK0pKQ8S6Wq8nZ64AXDoXJGv bfTtci7BhzxeWWV5ia08h+hvirCfumN09Ol7OrkyS8itqNqihWK04OCKrPQH5UkSpyuF sw2Q== X-Forwarded-Encrypted: i=1; AJvYcCXh9LkXGQWPUmQ1GfUDeeJH314Ji4WI7aLDKW+w0fJBCKR+y/gA/fNDTcZZcvIxQkWg7m+xIQ2IyEcpl5tWXC8rgEPn@vger.kernel.org X-Gm-Message-State: AOJu0YyjuunGBT/g5MN3XAiy7cqakyeRdrXL90axD8g6oCoa4GvV1MQX 5WQCwzFUqXt7qvq0rwo3e5W8Nw3jwyJEfmQXqdXh21U2Q/11DqIGYUQ= X-Gm-Gg: ATEYQzzMoDnbeE2eB/MO4Ac8BxDgueedGBsTtxP2j3rr4YN17Qp23T1Blp/bfBFqyhL X5le3TfzlPEZJbKBZiv0iNr3HNxffXUS61P7yR/aL9qVmmBq0iDfAZ/YlEnL6U12vuamybCKMMx 83ER685le95t/p6L7pmduNX5WvBcH5f2jL7M1dAvRutKgZb3eWm6of0l22uhCJxDLj9hbufwPTh woPhFYt4WjJD4Z4ifx4gZrrvh2ezPHdWmafwGoBvGqPbrqJWuY7B6fe4s2QYkhwf2rgsOHuq2mq KEZR89mIE+rA9jFvYcb6Cm6uSVwVhXTxGU+hQHX0gSP/fJRGyK50DiYjjmrR+VBswrm51NbnvL0 tn5k9E+/vLTwFTo1Jcl1KSi4Z/rj3c9yDNVY54stSRqKbyW5YWQAWh961jJ/pF9g4dMWUxq6ksG lDqZkBvnYVypi31jwe+2ZOp6aJ9fOAZefSytSDnjAD82VY9S3NlfwNdmXnlHQpSjc= X-Received: by 2002:a17:90b:3943:b0:359:915b:81f8 with SMTP id 98e67ed59e1d1-35a21fdd4fcmr12294858a91.18.1773675263998; Mon, 16 Mar 2026 08:34:23 -0700 (PDT) Received: from at-Standard-PC-Q35-ICH9-2009.. ([171.61.163.197]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35badb906c6sm2685a91.9.2026.03.16.08.34.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2026 08:34:22 -0700 (PDT) From: Atharva Tiwari To: Cc: Atharva Tiwari , Lukas Wunner , Ard Biesheuvel , Hans de Goede , =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org Subject: [PATCH v4 1/2] efi: Save Brightness using EFI on Macs Date: Mon, 16 Mar 2026 21:03:46 +0530 Message-ID: <20260316153407.1781-2-atharvatiwarilinuxdev@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260316153407.1781-1-atharvatiwarilinuxdev@gmail.com> References: <20260316153407.1781-1-atharvatiwarilinuxdev@gmail.com> Precedence: bulk X-Mailing-List: platform-driver-x86@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig index 29e0729299f5..243499a5d7b7 100644 --- a/drivers/firmware/efi/Kconfig +++ b/drivers/firmware/efi/Kconfig @@ -167,6 +167,16 @@ config APPLE_PROPERTIES If unsure, say Y if you have a Mac. Otherwise N. +config APPLE_BRIGHTNESS + bool "Apple Backlight control for EFI" + depends on X86 + help + This will save the brightness level to EFI, so brightness + level is preserved across reboots and shutdowns. allowing + for improved support of Apple hardware. + + If unsure, say Y if you have a Mac, otherwise N. + config RESET_ATTACK_MITIGATION bool "Reset memory attack mitigation" depends on EFI_STUB diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile index 8efbcf699e4f..1f5705cc87a2 100644 --- a/drivers/firmware/efi/Makefile +++ b/drivers/firmware/efi/Makefile @@ -26,6 +26,7 @@ obj-$(CONFIG_EFI_BOOTLOADER_CONTROL) += efibc.o obj-$(CONFIG_EFI_TEST) += test/ obj-$(CONFIG_EFI_DEV_PATH_PARSER) += dev-path-parser.o obj-$(CONFIG_APPLE_PROPERTIES) += apple-properties.o +obj-$(CONFIG_APPLE_BRIGHTNESS) += apple-brightness.o obj-$(CONFIG_EFI_RCI2_TABLE) += rci2-table.o obj-$(CONFIG_EFI_EMBEDDED_FIRMWARE) += embedded-firmware.o obj-$(CONFIG_LOAD_UEFI_KEYS) += mokvar-table.o diff --git a/drivers/firmware/efi/apple-brightness.c b/drivers/firmware/efi/apple-brightness.c new file mode 100644 index 000000000000..b060861b0795 --- /dev/null +++ b/drivers/firmware/efi/apple-brightness.c @@ -0,0 +1,67 @@ +// SPDX-License-Identifier: GPL-2.0-only OR MIT +/* + * apple-brightness.c - EFI brightness saver on Macs + * Copyright (C) 2026 Atharva Tiwari + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include + +static u32 efi_attr; +static u16 last_saved_level; + +static int (*get_brightness)(struct backlight_device *bl); +static struct backlight_device *bl_dev; + +void apple_brightness_shutdown(void) +{ + u16 level; + efi_status_t status; + + level = (u16)get_brightness(bl_dev); + + if (level == last_saved_level) + return; + + status = efivar_set_variable(APPLE_BRIGHTNESS_NAME, &APPLE_BRIGHTNESS_GUID, + efi_attr, sizeof(level), &level); + if (status != EFI_SUCCESS) + pr_debug("Unable to set brightness: 0x%lx\n", status); +} +EXPORT_SYMBOL(apple_brightness_shutdown); + +int apple_brightness_probe(struct backlight_device *bl, + int (*get_brightnessfn)(struct backlight_device *bl)) +{ + efi_status_t status; + unsigned long size = sizeof(last_saved_level); + int ret; + + bl_dev = bl; + get_brightness = get_brightnessfn; + + if (!efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE)) + return -ENODEV; + + ret = efivar_lock(); + if (ret) + return ret; + + status = efivar_get_variable(APPLE_BRIGHTNESS_NAME, &APPLE_BRIGHTNESS_GUID, + &efi_attr, &size, &last_saved_level); + + efivar_unlock(); + + if (status != EFI_SUCCESS) + return -ENODEV; + + return 0; +} +EXPORT_SYMBOL(apple_brightness_probe); + +MODULE_AUTHOR("Atharva Tiwari "); +MODULE_DESCRIPTION("EFI Brightness saver for Macs"); +MODULE_LICENSE("Dual MIT/GPL"); diff --git a/include/linux/platform_data/apple-brightness.h b/include/linux/platform_data/apple-brightness.h new file mode 100644 index 000000000000..54e3f3f8aa1c --- /dev/null +++ b/include/linux/platform_data/apple-brightness.h @@ -0,0 +1,20 @@ +/* SPDX-License-Identifier: GPL-2.0-only OR MIT */ +/* + * apple-brightness.h - EFI brightness saver for Macs + * Copyright (C) 2026 Atharva Tiwari + */ + +#ifndef _APPLE_BL_H_ +#define _APPLE_BL_H_ + +#include +#include + +#define APPLE_BRIGHTNESS_NAME L"backlight-level" +#define APPLE_BRIGHTNESS_GUID EFI_GUID(0x7c436110, 0xab2a, 0x4bbb, 0xa8, 0x80, 0xfe, 0x41, 0x99, 0x5c, 0x9f, 0x82) + +int apple_brightness_probe(struct backlight_device *bl, + int (*get_brightnessfn)(struct backlight_device *bl)); + +void apple_brightness_shutdown(void); +#endif /* _APPLE_BL_H */ -- 2.43.0