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Date:      Tue, 3 Feb 2026 07:33:48 +0200
From:      Konstantin Belousov <kostikbel@gmail.com>
To:        Adrian Chadd <adrian@freebsd.org>
Cc:        src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org, Abdelkader Boudih <freebsd@seuros.com>
Subject:   Re: git: 052a791b0055 - main - acpi: add Darwin OSI quirk for Apple Mac hardware
Message-ID:  <aYGIvC3v0zQCJrGo@kib.kiev.ua>
In-Reply-To: <698154c0.35e9d.2d7b8775@gitrepo.freebsd.org>
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On Tue, Feb 03, 2026 at 01:52:00AM +0000, Adrian Chadd wrote:
> The branch main has been updated by adrian:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=052a791b00555805f19ccc38a04d42d48b54104b
> 
> commit 052a791b00555805f19ccc38a04d42d48b54104b
> Author:     Abdelkader Boudih <freebsd@seuros.com>
> AuthorDate: 2026-02-03 01:43:00 +0000
> Commit:     Adrian Chadd <adrian@FreeBSD.org>
> CommitDate: 2026-02-03 01:51:37 +0000
> 
>     acpi: add Darwin OSI quirk for Apple Mac hardware
>     
>     Mac firmware hides the Intel integrated GPU (iGPU) on dual GPU x86
>     systems, i.e., with AMD/NVIDIA dGPUs, when the Darwin OSI is not
>     installed via ACPI.
>     
>     Prior to this change, FreeBSD always used the dGPU. This is fine in
>     practice, but consumed more power than when the iGPU is used,
>     resulting in reduced battery life.
>     
>     Linux handles this in `drivers/acpi/osi.c` by detecting Apple
>     hardware via DMI, disabling all Windows OSI strings, and
>     by explicitly installing the Darwin OSI ACPI handler. This change
>     applies equivalent logic to the acpi(4) driver on FreeBSD.
>     
>     This feature can be enabled/disabled using the
>     `hw.acpi.apple_darwin_osi` tunable. Setting this tunable to `0`
>     restores the previous behavior by explicitly disabling the added
>     support.
>     
>     Reviewed by:    obiwac, ngie, adrian
>     Differential Revision:  https://reviews.freebsd.org/D54762
> ---
>  sys/dev/acpica/acpi.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 72 insertions(+)
> 
> diff --git a/sys/dev/acpica/acpi.c b/sys/dev/acpica/acpi.c
> index 60a2dba91b05..8cdb73333462 100644
> --- a/sys/dev/acpica/acpi.c
> +++ b/sys/dev/acpica/acpi.c
> @@ -293,6 +293,17 @@ static char acpi_remove_interface[256];
>  TUNABLE_STR("hw.acpi.remove_interface", acpi_remove_interface,
>      sizeof(acpi_remove_interface));
>  
> +/*
> + * Automatically apply the Darwin OSI on Apple Mac hardware to obtain
> + * access to full ACPI hardware support on supported platforms.
> + *
> + * This flag automatically overrides any values set by
> + * `hw.acpi.acpi_install_interface` and unset by
> + * `hw.acpi.acpi_remove_interface`.
> + */
> +static int acpi_apple_darwin_osi = 1;
> +TUNABLE_INT("hw.acpi.apple_darwin_osi", &acpi_apple_darwin_osi);
> +
>  /* Allow users to dump Debug objects without ACPI debugger. */
>  static int acpi_debug_objects;
>  TUNABLE_INT("debug.acpi.enable_debug_objects", &acpi_debug_objects);
> @@ -4903,6 +4914,67 @@ acpi_reset_interfaces(device_t dev)
>  		}
>  		acpi_free_interfaces(&list);
>  	}
> +
> +	/*
> +	 * Apple Mac hardware quirk: install Darwin OSI.
> +	 *
> +	 * On Apple hardware, install the Darwin OSI and remove the Windows OSI
> +	 * to match Linux behavior.
> +	 *
> +	 * This is required for dual-GPU MacBook Pro systems
> +	 * (Intel iGPU + AMD/NVIDIA dGPU) where the iGPU is hidden when the
> +	 * firmware doesn't see Darwin OSI, but it also unlocks additional ACPI
> +	 * support on non-MacBook Pro Apple platforms.
> +	 *
> +	 * Apple's ACPI firmware checks _OSI("Darwin") and sets OSYS=10000
> +	 * for macOS. Many device methods use OSDW() which checks OSYS==10000
> +	 * for macOS-specific behavior including GPU visibility and power
> +	 * management.
> +	 *
> +	 * Linux enables Darwin OSI by default on Apple hardware and disables
> +	 * all Windows OSI strings (drivers/acpi/osi.c). Users can override
> +	 * this behavior with acpi_osi=!Darwin to get Windows-like behavior,
> +	 * in general, but this logic makes that process unnecessary.
> +	 *
> +	 * Detect Apple via SMBIOS and enable Darwin while disabling Windows
> +	 * vendor strings. This makes both GPUs visible on dual-GPU MacBook Pro
> +	 * systems (Intel iGPU + AMD dGPU) and unlocks full platform
> +	 * ACPI support.
> +	 */
> +	if (acpi_apple_darwin_osi) {
> +		char *vendor = kern_getenv("smbios.system.maker");
> +		if (vendor != NULL) {
> +			if (strcmp(vendor, "Apple Inc.") == 0 ||
> +			    strcmp(vendor, "Apple Computer, Inc.") == 0) {
> +				/* Disable all other OSI vendor strings. */
> +				status = AcpiUpdateInterfaces(
> +				    ACPI_DISABLE_ALL_VENDOR_STRINGS);
> +				/* Install Darwin */
> +				if (ACPI_SUCCESS(status)) {
> +					status = AcpiInstallInterface("Darwin");
> +				}
> +				if (bootverbose) {
> +					if (ACPI_SUCCESS(status)) {
> +						device_printf(dev,
> +						    "Apple hardware: installed Darwin "
> +						    "OSI and removed other vendor OSI "
> +						    "(Windows, etc)\n");
Why this verbosity is needed?

I see no benefit from it, other then consuming kernel memory.

> +					} else {
> +						device_printf(dev,
> +						    "Apple hardware: failed to install "
> +						    "Darwin OSI: %s\n",
> +						    AcpiFormatException(
> +							status));
> +					}
> +				}
> +			} else if (bootverbose) {
> +				device_printf(dev,
> +				    "Not installing Darwin OSI on unsupported platform: %s\n",
> +				    vendor);
> +			}
> +			freeenv(vendor);
> +		}
> +	}
>  }
>  
>  static int
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