Merge patch series "rust: auxiliary: replace drvdata() with registration data"

Danilo Krummrich <dakr@kernel.org> says:

When drvdata() was introduced in commit 6f61a2637abe ("rust: device: introduce
Device::drvdata()"), its commit message already noted that a direct accessor to
the driver's bus device private data is not commonly required -- bus callbacks
provide access through &self, and other entry points (IRQs, workqueues, IOCTLs,
etc.) carry their own private data.

The sole motivation for drvdata() was inter-driver interaction, e.g. a parent
driver deriving its bus device private data from the child driver via the
auxiliary bus.

However, drvdata() exposes the driver's bus device private data beyond the
driver's own scope. This creates ordering constraints -- drvdata may not be set
yet when the first caller of drvdata() can appear -- and forces the driver's bus
device private data to outlive all registrations that access it; a requirement
that causes unnecessary complications.

Private data should be private to the entity that issues it; bus device private
data belongs to bus callbacks, class device private data to class callbacks, IRQ
private data to the IRQ handler, etc.

This series replaces drvdata() with a dedicated registration_data pointer on
struct auxiliary_device. The parent stores its private data explicitly during
registration; the data is private to the registration and lives as long as the
Registration object.

On teardown, Registration::drop() first triggers auxiliary_device_delete()
(unbinding the child), then frees the registration data. Ordering constraints
are structural -- the child's lifecycle is scoped to the registration by
construction, not by convention.

With no remaining use case for drvdata(), drvdata(), match_type_id(),
set_type_id() and struct driver_type are removed.

This is a prerequisite for [1], which builds on the removal of drvdata() to
enable Higher-Ranked Lifetime Types (HRT) for Rust device drivers.

[1] https://lore.kernel.org/driver-core/20260427221155.2144848-1-dakr@kernel.org/

Link: https://patch.msgid.link/20260505152400.3905096-1-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 0 insertions, 16 deletions

diff --git a/drivers/base/base.h b/drivers/base/base.h
index 0ed1e278b957..483b99b4fa3d 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -86,18 +86,6 @@ struct driver_private {
 };
 #define to_driver(obj) container_of(obj, struct driver_private, kobj)
 
-#ifdef CONFIG_RUST
-/**
- * struct driver_type - Representation of a Rust driver type.
- */
-struct driver_type {
-	/**
-	 * @id: Representation of core::any::TypeId.
-	 */
-	u8 id[16];
-} __packed;
-#endif
-
 /**
  * struct device_private - structure to hold the private to the driver core
  *			   portions of the device structure.
@@ -115,7 +103,6 @@ struct driver_type {
  *			   dev_err_probe() for later retrieval via debugfs
  * @device: pointer back to the struct device that this structure is
  *	    associated with.
- * @driver_type: The type of the bound Rust driver.
  * @dead: This device is currently either in the process of or has been
  *	  removed from the system. Any asynchronous events scheduled for this
  *	  device should exit without taking any action.
@@ -132,9 +119,6 @@ struct device_private {
 	const struct device_driver *async_driver;
 	char *deferred_probe_reason;
 	struct device *device;
-#ifdef CONFIG_RUST
-	struct driver_type driver_type;
-#endif
 	u8 dead:1;
 };
 #define to_device_private_parent(obj)	\