[PATCH v1 0/2] ACPI: bus: Remove struct acpi_driver from the kernel

[PATCH v1 0/2] ACPI: bus: Remove struct acpi_driver from the kernel

[Rafael J. Wysocki (Intel)]

Hi All,

After converting all of the drivers using the struct acpi_driver interface to
proper platform drivers, that interface can be dropped now, which is done in
this series (patch [1/2]).

Additionally, the no_pm flag is set for all struct acpi_device object since
they are not going to be directly involved in any kind of power management
now (that is, they will not have PM-aware drivers and they will not be
included in PM domains).

Thanks!

[PATCH v1 1/2] 1/2] ACPI: bus: Eliminate struct acpi_driver

[Rafael J. Wysocki]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

Now that struct acpi_driver has no more users, eliminate it along with
all of the code related to it.

Also remove the file added by commit b8c8a8ea18ad ("ACPI: Documentation:
driver-api: Disapprove of using ACPI drivers") because it will not be
necessary any more after eliminating struct acpi_driver from the code.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 .../driver-api/acpi/acpi-drivers.rst          |  80 ----------
 Documentation/driver-api/acpi/index.rst       |   1 -
 drivers/acpi/bus.c                            | 138 +-----------------
 drivers/acpi/power.c                          |   1 -
 drivers/acpi/scan.c                           |  16 +-
 include/acpi/acpi_bus.h                       |  50 +------
 6 files changed, 5 insertions(+), 281 deletions(-)
 delete mode 100644 Documentation/driver-api/acpi/acpi-drivers.rst

diff --git a/Documentation/driver-api/acpi/acpi-drivers.rst b/Documentation/driver-api/acpi/acpi-drivers.rst
deleted file mode 100644
index 376b6d8a678c..000000000000
--- a/Documentation/driver-api/acpi/acpi-drivers.rst
+++ /dev/null
@@ -1,80 +0,0 @@
-.. SPDX-License-Identifier: GPL-2.0
-.. include:: <isonum.txt>
-
-=========================================
-Why using ACPI drivers is not a good idea
-=========================================
-
-:Copyright: |copy| 2026, Intel Corporation
-
-:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
-
-Even though binding drivers directly to struct acpi_device objects, also
-referred to as "ACPI device nodes", allows basic functionality to be provided
-at least in some cases, there are problems with it, related to general
-consistency, sysfs layout, power management operation ordering, and code
-cleanliness.
-
-First of all, ACPI device nodes represent firmware entities rather than
-hardware and in many cases they provide auxiliary information on devices
-enumerated independently (like PCI devices or CPUs).  It is therefore generally
-questionable to assign resources to them because the entities represented by
-them do not decode addresses in the memory or I/O address spaces and do not
-generate interrupts or similar (all of that is done by hardware).
-
-Second, as a general rule, a struct acpi_device can only be a parent of another
-struct acpi_device.  If that is not the case, the location of the child device
-in the device hierarchy is at least confusing and it may not be straightforward
-to identify the piece of hardware providing functionality represented by it.
-However, binding a driver directly to an ACPI device node may cause that to
-happen if the given driver registers input devices or wakeup sources under it,
-for example.
-
-Next, using system suspend and resume callbacks directly on ACPI device nodes
-is also questionable because it may cause ordering problems to appear.  Namely,
-ACPI device nodes are registered before enumerating hardware corresponding to
-them and they land on the PM list in front of the majority of other device
-objects.  Consequently, the execution ordering of their PM callbacks may be
-different from what is generally expected.  Also, in general, dependencies
-returned by _DEP objects do not affect ACPI device nodes themselves, but the
-"physical" devices associated with them, which potentially is one more source
-of inconsistency related to treating ACPI device nodes as "real" device
-representation.
-
-All of the above means that binding drivers to ACPI device nodes should
-generally be avoided and so struct acpi_driver objects should not be used.
-
-Moreover, a device ID is necessary to bind a driver directly to an ACPI device
-node, but device IDs are not generally associated with all of them.  Some of
-them contain alternative information allowing the corresponding pieces of
-hardware to be identified, for example represented by an _ADR object return
-value, and device IDs are not used in those cases.  In consequence, confusingly
-enough, binding an ACPI driver to an ACPI device node may even be impossible.
-
-When that happens, the piece of hardware corresponding to the given ACPI device
-node is represented by another device object, like a struct pci_dev, and the
-ACPI device node is the "ACPI companion" of that device, accessible through its
-fwnode pointer used by the ACPI_COMPANION() macro.  The ACPI companion holds
-additional information on the device configuration and possibly some "recipes"
-on device manipulation in the form of AML (ACPI Machine Language) bytecode
-provided by the platform firmware.  Thus the role of the ACPI device node is
-similar to the role of a struct device_node on a system where Device Tree is
-used for platform description.
-
-For consistency, this approach has been extended to the cases in which ACPI
-device IDs are used.  Namely, in those cases, an additional device object is
-created to represent the piece of hardware corresponding to a given ACPI device
-node.  By default, it is a platform device, but it may also be a PNP device, a
-CPU device, or another type of device, depending on what the given piece of
-hardware actually is.  There are even cases in which multiple devices are
-"backed" or "accompanied" by one ACPI device node (e.g. ACPI device nodes
-corresponding to GPUs that may provide firmware interfaces for backlight
-brightness control in addition to GPU configuration information).
-
-This means that it really should never be necessary to bind a driver directly to
-an ACPI device node because there is a "proper" device object representing the
-corresponding piece of hardware that can be bound to by a "proper" driver using
-the given ACPI device node as the device's ACPI companion.  Thus, in principle,
-there is no reason to use ACPI drivers and if they all were replaced with other
-driver types (for example, platform drivers), some code could be dropped and
-some complexity would go away.
diff --git a/Documentation/driver-api/acpi/index.rst b/Documentation/driver-api/acpi/index.rst
index 2b10d83f9994..ace0008e54c2 100644
--- a/Documentation/driver-api/acpi/index.rst
+++ b/Documentation/driver-api/acpi/index.rst
@@ -7,4 +7,3 @@ ACPI Support
 
    linuxized-acpica
    scan_handlers
-   acpi-drivers
diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index a30a904f6535..fae79cdd3610 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -620,41 +620,6 @@ static void acpi_bus_notify(acpi_handle handle, u32 type, void *data)
 	acpi_evaluate_ost(handle, type, ACPI_OST_SC_NON_SPECIFIC_FAILURE, NULL);
 }
 
-static void acpi_notify_device(acpi_handle handle, u32 event, void *data)
-{
-	struct acpi_device *device = data;
-	struct acpi_driver *acpi_drv = to_acpi_driver(device->dev.driver);
-
-	acpi_drv->ops.notify(device, event);
-}
-
-static int acpi_device_install_notify_handler(struct acpi_device *device,
-					      struct acpi_driver *acpi_drv)
-{
-	u32 type = acpi_drv->flags & ACPI_DRIVER_ALL_NOTIFY_EVENTS ?
-				ACPI_ALL_NOTIFY : ACPI_DEVICE_NOTIFY;
-	acpi_status status;
-
-	status = acpi_install_notify_handler(device->handle, type,
-					     acpi_notify_device, device);
-	if (ACPI_FAILURE(status))
-		return -EINVAL;
-
-	return 0;
-}
-
-static void acpi_device_remove_notify_handler(struct acpi_device *device,
-					      struct acpi_driver *acpi_drv)
-{
-	u32 type = acpi_drv->flags & ACPI_DRIVER_ALL_NOTIFY_EVENTS ?
-				ACPI_ALL_NOTIFY : ACPI_DEVICE_NOTIFY;
-
-	acpi_remove_notify_handler(device->handle, type,
-				   acpi_notify_device);
-
-	acpi_os_wait_events_complete();
-}
-
 int acpi_dev_install_notify_handler(struct acpi_device *adev,
 				    u32 handler_type,
 				    acpi_notify_handler handler, void *context)
@@ -1121,57 +1086,13 @@ bool acpi_driver_match_device(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(acpi_driver_match_device);
 
-/* --------------------------------------------------------------------------
-                              ACPI Driver Management
-   -------------------------------------------------------------------------- */
-
-/**
- * __acpi_bus_register_driver - register a driver with the ACPI bus
- * @driver: driver being registered
- * @owner: owning module/driver
- *
- * Registers a driver with the ACPI bus.  Searches the namespace for all
- * devices that match the driver's criteria and binds.  Returns zero for
- * success or a negative error status for failure.
- */
-int __acpi_bus_register_driver(struct acpi_driver *driver, struct module *owner)
-{
-	if (acpi_disabled)
-		return -ENODEV;
-	driver->drv.name = driver->name;
-	driver->drv.bus = &acpi_bus_type;
-	driver->drv.owner = owner;
-
-	return driver_register(&driver->drv);
-}
-
-EXPORT_SYMBOL(__acpi_bus_register_driver);
-
-/**
- * acpi_bus_unregister_driver - unregisters a driver with the ACPI bus
- * @driver: driver to unregister
- *
- * Unregisters a driver with the ACPI bus.  Searches the namespace for all
- * devices that match the driver's criteria and unbinds.
- */
-void acpi_bus_unregister_driver(struct acpi_driver *driver)
-{
-	driver_unregister(&driver->drv);
-}
-
-EXPORT_SYMBOL(acpi_bus_unregister_driver);
-
 /* --------------------------------------------------------------------------
                               ACPI Bus operations
    -------------------------------------------------------------------------- */
 
 static int acpi_bus_match(struct device *dev, const struct device_driver *drv)
 {
-	struct acpi_device *acpi_dev = to_acpi_device(dev);
-	const struct acpi_driver *acpi_drv = to_acpi_driver(drv);
-
-	return acpi_dev->flags.match_driver
-		&& !acpi_match_device_ids(acpi_dev, acpi_drv->ids);
+	return 0;
 }
 
 static int acpi_device_uevent(const struct device *dev, struct kobj_uevent_env *env)
@@ -1179,66 +1100,9 @@ static int acpi_device_uevent(const struct device *dev, struct kobj_uevent_env *
 	return __acpi_device_uevent_modalias(to_acpi_device(dev), env);
 }
 
-static int acpi_device_probe(struct device *dev)
-{
-	struct acpi_device *acpi_dev = to_acpi_device(dev);
-	struct acpi_driver *acpi_drv = to_acpi_driver(dev->driver);
-	int ret;
-
-	if (acpi_dev->handler && !acpi_is_pnp_device(acpi_dev))
-		return -EINVAL;
-
-	if (!acpi_drv->ops.add)
-		return -ENOSYS;
-
-	ret = acpi_drv->ops.add(acpi_dev);
-	if (ret) {
-		acpi_dev->driver_data = NULL;
-		return ret;
-	}
-
-	pr_debug("Driver [%s] successfully bound to device [%s]\n",
-		 acpi_drv->name, acpi_dev->pnp.bus_id);
-
-	if (acpi_drv->ops.notify) {
-		ret = acpi_device_install_notify_handler(acpi_dev, acpi_drv);
-		if (ret) {
-			if (acpi_drv->ops.remove)
-				acpi_drv->ops.remove(acpi_dev);
-
-			acpi_dev->driver_data = NULL;
-			return ret;
-		}
-	}
-
-	pr_debug("Found driver [%s] for device [%s]\n", acpi_drv->name,
-		 acpi_dev->pnp.bus_id);
-
-	get_device(dev);
-	return 0;
-}
-
-static void acpi_device_remove(struct device *dev)
-{
-	struct acpi_device *acpi_dev = to_acpi_device(dev);
-	struct acpi_driver *acpi_drv = to_acpi_driver(dev->driver);
-
-	if (acpi_drv->ops.notify)
-		acpi_device_remove_notify_handler(acpi_dev, acpi_drv);
-
-	if (acpi_drv->ops.remove)
-		acpi_drv->ops.remove(acpi_dev);
-
-	acpi_dev->driver_data = NULL;
-
-	put_device(dev);
-}
-
 const struct bus_type acpi_bus_type = {
 	.name		= "acpi",
 	.match		= acpi_bus_match,
-	.probe		= acpi_device_probe,
-	.remove		= acpi_device_remove,
 	.uevent		= acpi_device_uevent,
 };
 
diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
index d4131c184be8..23a4e207a01e 100644
--- a/drivers/acpi/power.c
+++ b/drivers/acpi/power.c
@@ -954,7 +954,6 @@ struct acpi_device *acpi_add_power_resource(acpi_handle handle)
 	INIT_LIST_HEAD(&resource->list_node);
 	INIT_LIST_HEAD(&resource->dependents);
 	device->power.state = ACPI_STATE_UNKNOWN;
-	device->flags.match_driver = true;
 
 	/* Evaluate the object to get the system level and resource order. */
 	status = acpi_evaluate_object(handle, NULL, NULL, &buffer);
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 9a7ac2eb9ce0..ee24c65d43ed 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -273,13 +273,9 @@ static int acpi_scan_check_and_detach(struct acpi_device *adev, void *p)
 		}
 	}
 
-	adev->flags.match_driver = false;
-	if (handler) {
-		if (handler->detach)
-			handler->detach(adev);
-	} else {
-		device_release_driver(&adev->dev);
-	}
+	if (handler && handler->detach)
+		handler->detach(adev);
+
 	/*
 	 * Most likely, the device is going away, so put it into D3cold before
 	 * that.
@@ -1821,7 +1817,6 @@ void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
 	acpi_set_pnp_ids(handle, &device->pnp, type);
 	acpi_init_properties(device);
 	acpi_bus_get_flags(device);
-	device->flags.match_driver = false;
 	device->flags.initialized = true;
 	device->flags.enumeration_by_parent =
 		acpi_device_enumeration_by_parent(device);
@@ -2375,16 +2370,11 @@ static int acpi_bus_attach(struct acpi_device *device, void *first_pass)
 	if (ret < 0)
 		return 0;
 
-	device->flags.match_driver = true;
 	if (ret > 0 && !device->flags.enumeration_by_parent) {
 		acpi_device_set_enumerated(device);
 		goto ok;
 	}
 
-	ret = device_attach(&device->dev);
-	if (ret < 0)
-		return 0;
-
 	if (device->pnp.type.platform_id || device->pnp.type.backlight ||
 	    device->flags.enumeration_by_parent)
 		acpi_default_enumeration(device);
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 714d111d8053..7b8051baed75 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -108,7 +108,6 @@ enum acpi_bus_device_type {
 	ACPI_BUS_DEVICE_TYPE_COUNT
 };
 
-struct acpi_driver;
 struct acpi_device;
 
 /*
@@ -158,32 +157,6 @@ struct acpi_hotplug_context {
 	acpi_hp_fixup fixup;
 };
 
-/*
- * ACPI Driver
- * -----------
- */
-
-typedef int (*acpi_op_add) (struct acpi_device * device);
-typedef void (*acpi_op_remove) (struct acpi_device *device);
-typedef void (*acpi_op_notify) (struct acpi_device * device, u32 event);
-
-struct acpi_device_ops {
-	acpi_op_add add;
-	acpi_op_remove remove;
-	acpi_op_notify notify;
-};
-
-#define ACPI_DRIVER_ALL_NOTIFY_EVENTS	0x1	/* system AND device events */
-
-struct acpi_driver {
-	char name[80];
-	char class[80];
-	const struct acpi_device_id *ids; /* Supported Hardware IDs */
-	unsigned int flags;
-	struct acpi_device_ops ops;
-	struct device_driver drv;
-};
-
 /*
  * ACPI Device
  * -----------
@@ -211,7 +184,6 @@ struct acpi_device_flags {
 	u32 removable:1;
 	u32 ejectable:1;
 	u32 power_manageable:1;
-	u32 match_driver:1;
 	u32 initialized:1;
 	u32 visited:1;
 	u32 hotplug_notify:1;
@@ -221,7 +193,7 @@ struct acpi_device_flags {
 	u32 cca_seen:1;
 	u32 enumeration_by_parent:1;
 	u32 honor_deps:1;
-	u32 reserved:18;
+	u32 reserved:19;
 };
 
 /* File System */
@@ -570,7 +542,6 @@ static inline void *acpi_driver_data(struct acpi_device *d)
 }
 
 #define to_acpi_device(d)	container_of(d, struct acpi_device, dev)
-#define to_acpi_driver(d)	container_of_const(d, struct acpi_driver, drv)
 
 static inline struct acpi_device *acpi_dev_parent(struct acpi_device *adev)
 {
@@ -676,13 +647,6 @@ void acpi_scan_lock_release(void);
 void acpi_lock_hp_context(void);
 void acpi_unlock_hp_context(void);
 int acpi_scan_add_handler(struct acpi_scan_handler *handler);
-/*
- * use a macro to avoid include chaining to get THIS_MODULE
- */
-#define acpi_bus_register_driver(drv) \
-	__acpi_bus_register_driver(drv, THIS_MODULE)
-int __acpi_bus_register_driver(struct acpi_driver *driver, struct module *owner);
-void acpi_bus_unregister_driver(struct acpi_driver *driver);
 int acpi_bus_scan(acpi_handle handle);
 void acpi_bus_trim(struct acpi_device *start);
 acpi_status acpi_bus_get_ejd(acpi_handle handle, acpi_handle * ejd);
@@ -696,18 +660,6 @@ static inline bool acpi_device_enumerated(struct acpi_device *adev)
 	return adev && adev->flags.initialized && adev->flags.visited;
 }
 
-/**
- * module_acpi_driver(acpi_driver) - Helper macro for registering an ACPI driver
- * @__acpi_driver: acpi_driver struct
- *
- * Helper macro for ACPI drivers which do not do anything special in module
- * init/exit. This eliminates a lot of boilerplate. Each module may only
- * use this macro once, and calling it replaces module_init() and module_exit()
- */
-#define module_acpi_driver(__acpi_driver) \
-	module_driver(__acpi_driver, acpi_bus_register_driver, \
-		      acpi_bus_unregister_driver)
-
 /*
  * Bind physical devices with ACPI devices
  */
-- 
2.51.0

[PATCH v1 2/2] ACPI: scan: Set power.no_pm for all struct acpi_device objects

[Rafael J. Wysocki]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

Now that drivers do not bind to ACPI device objects, there is no reason
for them to be included directly in power management in any way, so set
power.no_pm for all of them.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/scan.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index ee24c65d43ed..8515e1892643 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1811,6 +1811,7 @@ void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
 	device->dev.release = release;
 	device->dev.bus = &acpi_bus_type;
 	device->dev.groups = acpi_groups;
+	device_set_pm_not_required(&device->dev);
 	fwnode_init(&device->fwnode, &acpi_device_fwnode_ops);
 	acpi_set_device_status(device, ACPI_STA_DEFAULT);
 	acpi_device_get_busid(device);
-- 
2.51.0

Re: [PATCH v1 0/2] ACPI: bus: Remove struct acpi_driver from the kernel

[Andy Shevchenko]

On Wed, Jul 01, 2026 at 09:15:27PM +0200, Rafael J. Wysocki (Intel) wrote:
> Hi All,
> 
> After converting all of the drivers using the struct acpi_driver interface to
> proper platform drivers, that interface can be dropped now, which is done in
> this series (patch [1/2]).

What a nice result!

> Additionally, the no_pm flag is set for all struct acpi_device object since
> they are not going to be directly involved in any kind of power management
> now (that is, they will not have PM-aware drivers and they will not be
> included in PM domains).

I am in favour of this cleanup!
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v1 0/2] ACPI: bus: Remove struct acpi_driver from the kernel

[Rafael J. Wysocki (Intel)]

On Thu, Jul 2, 2026 at 11:15 AM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Wed, Jul 01, 2026 at 09:15:27PM +0200, Rafael J. Wysocki (Intel) wrote:
> > Hi All,
> >
> > After converting all of the drivers using the struct acpi_driver interface to
> > proper platform drivers, that interface can be dropped now, which is done in
> > this series (patch [1/2]).
>
> What a nice result!
>
> > Additionally, the no_pm flag is set for all struct acpi_device object since
> > they are not going to be directly involved in any kind of power management
> > now (that is, they will not have PM-aware drivers and they will not be
> > included in PM domains).
>
> I am in favour of this cleanup!
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Thank you!