Merge branch 'acpi-bus'

Merge ACPI bus type driver updates for 6.7-rc1:

 - Add context argument to acpi_dev_install_notify_handler() (Rafael
   Wysocki).

 - Clarify ACPI bus concepts in the ACPI device enumeration
   documentation (Rafael Wysocki).

* acpi-bus:
  ACPI: bus: Add context argument to acpi_dev_install_notify_handler()
  ACPI: docs: enumeration: Clarify ACPI bus concepts

9 files changed, 52 insertions, 9 deletions

diff --git a/Documentation/firmware-guide/acpi/enumeration.rst b/Documentation/firmware-guide/acpi/enumeration.rst
index 56d9913a3370..d79f69390991 100644
--- a/Documentation/firmware-guide/acpi/enumeration.rst
+++ b/Documentation/firmware-guide/acpi/enumeration.rst
@@ -64,6 +64,49 @@ If the driver needs to perform more complex initialization like getting and
 configuring GPIOs it can get its ACPI handle and extract this information
 from ACPI tables.
 
+ACPI device objects
+===================
+
+Generally speaking, there are two categories of devices in a system in which
+ACPI is used as an interface between the platform firmware and the OS: Devices
+that can be discovered and enumerated natively, through a protocol defined for
+the specific bus that they are on (for example, configuration space in PCI),
+without the platform firmware assistance, and devices that need to be described
+by the platform firmware so that they can be discovered.  Still, for any device
+known to the platform firmware, regardless of which category it falls into,
+there can be a corresponding ACPI device object in the ACPI Namespace in which
+case the Linux kernel will create a struct acpi_device object based on it for
+that device.
+
+Those struct acpi_device objects are never used for binding drivers to natively
+discoverable devices, because they are represented by other types of device
+objects (for example, struct pci_dev for PCI devices) that are bound to by
+device drivers (the corresponding struct acpi_device object is then used as
+an additional source of information on the configuration of the given device).
+Moreover, the core ACPI device enumeration code creates struct platform_device
+objects for the majority of devices that are discovered and enumerated with the
+help of the platform firmware and those platform device objects can be bound to
+by platform drivers in direct analogy with the natively enumerable devices
+case.  Therefore it is logically inconsistent and so generally invalid to bind
+drivers to struct acpi_device objects, including drivers for devices that are
+discovered with the help of the platform firmware.
+
+Historically, ACPI drivers that bound directly to struct acpi_device objects
+were implemented for some devices enumerated with the help of the platform
+firmware, but this is not recommended for any new drivers.  As explained above,
+platform device objects are created for those devices as a rule (with a few
+exceptions that are not relevant here) and so platform drivers should be used
+for handling them, even though the corresponding ACPI device objects are the
+only source of device configuration information in that case.
+
+For every device having a corresponding struct acpi_device object, the pointer
+to it is returned by the ACPI_COMPANION() macro, so it is always possible to
+get to the device configuration information stored in the ACPI device object
+this way.  Accordingly, struct acpi_device can be regarded as a part of the
+interface between the kernel and the ACPI Namespace, whereas device objects of
+other types (for example, struct pci_dev or struct platform_device) are used
+for interacting with the rest of the system.
+
 DMA support
 ===========
 
diff --git a/drivers/acpi/ac.c b/drivers/acpi/ac.c
index 225dc6818751..aac3e561790c 100644
--- a/drivers/acpi/ac.c
+++ b/drivers/acpi/ac.c
@@ -257,7 +257,7 @@ static int acpi_ac_add(struct acpi_device *device)
 	register_acpi_notifier(&ac->battery_nb);
 
 	result = acpi_dev_install_notify_handler(device, ACPI_ALL_NOTIFY,
-						 acpi_ac_notify);
+						 acpi_ac_notify, device);
 	if (result)
 		goto err_unregister;
 
diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index b411948594ff..0b7a01f38b65 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -2062,7 +2062,7 @@ static int acpi_video_bus_add(struct acpi_device *device)
 		goto err_del;
 
 	error = acpi_dev_install_notify_handler(device, ACPI_DEVICE_NOTIFY,
-						acpi_video_bus_notify);
+						acpi_video_bus_notify, device);
 	if (error)
 		goto err_remove;
 
diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index 969bf81e8d54..b379401ff1c2 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -1214,7 +1214,7 @@ static int acpi_battery_add(struct acpi_device *device)
 	device_init_wakeup(&device->dev, 1);
 
 	result = acpi_dev_install_notify_handler(device, ACPI_ALL_NOTIFY,
-						 acpi_battery_notify);
+						 acpi_battery_notify, device);
 	if (result)
 		goto fail_pm;
 
diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index a4aa53b7e2bb..72e64c0718c9 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -556,12 +556,12 @@ static void acpi_device_remove_notify_handler(struct acpi_device *device,
 
 int acpi_dev_install_notify_handler(struct acpi_device *adev,
 				    u32 handler_type,
-				    acpi_notify_handler handler)
+				    acpi_notify_handler handler, void *context)
 {
 	acpi_status status;
 
 	status = acpi_install_notify_handler(adev->handle, handler_type,
-					     handler, adev);
+					     handler, context);
 	if (ACPI_FAILURE(status))
 		return -ENODEV;
 
diff --git a/drivers/acpi/hed.c b/drivers/acpi/hed.c
index 46c6f8c35b43..7652515a6be1 100644
--- a/drivers/acpi/hed.c
+++ b/drivers/acpi/hed.c
@@ -57,7 +57,7 @@ static int acpi_hed_add(struct acpi_device *device)
 	hed_handle = device->handle;
 
 	err = acpi_dev_install_notify_handler(device, ACPI_DEVICE_NOTIFY,
-					      acpi_hed_notify);
+					      acpi_hed_notify, device);
 	if (err)
 		hed_handle = NULL;
 
diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index 7d88db451cfb..992385537757 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -3340,7 +3340,7 @@ static int acpi_nfit_add(struct acpi_device *adev)
 	int rc = 0;
 
 	rc = acpi_dev_install_notify_handler(adev, ACPI_DEVICE_NOTIFY,
-					     acpi_nfit_notify);
+					     acpi_nfit_notify, adev);
 	if (rc)
 		return rc;
 
diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index 42a3df9d625d..c3143ee5e825 100644
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -970,7 +970,7 @@ static int acpi_thermal_add(struct acpi_device *device)
 		acpi_device_bid(device), deci_kelvin_to_celsius(tz->temperature));
 
 	result = acpi_dev_install_notify_handler(device, ACPI_DEVICE_NOTIFY,
-						 acpi_thermal_notify);
+						 acpi_thermal_notify, device);
 	if (result)
 		goto flush_wq;
 
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 20c637687086..afeed6e72049 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -520,7 +520,7 @@ int acpi_bus_attach_private_data(acpi_handle, void *);
 void acpi_bus_detach_private_data(acpi_handle);
 int acpi_dev_install_notify_handler(struct acpi_device *adev,
 				    u32 handler_type,
-				    acpi_notify_handler handler);
+				    acpi_notify_handler handler, void *context);
 void acpi_dev_remove_notify_handler(struct acpi_device *adev,
 				    u32 handler_type,
 				    acpi_notify_handler handler);