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Message-ID: <20260116081036.352286-20-tzungbi@kernel.org>
Date: Fri, 16 Jan 2026 08:10:32 +0000
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Benson Leung <bleung@...omium.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J . Wysocki" <rafael@...nel.org>,
Danilo Krummrich <dakr@...nel.org>,
Bartosz Golaszewski <brgl@...ev.pl>,
Linus Walleij <linusw@...nel.org>
Cc: Jonathan Corbet <corbet@....net>,
Shuah Khan <shuah@...nel.org>,
linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org,
chrome-platform@...ts.linux.dev,
linux-kselftest@...r.kernel.org,
tzungbi@...nel.org,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Wolfram Sang <wsa+renesas@...g-engineering.com>,
Simona Vetter <simona.vetter@...ll.ch>,
Dan Williams <dan.j.williams@...el.com>,
Jason Gunthorpe <jgg@...dia.com>,
linux-gpio@...r.kernel.org
Subject: [PATCH 19/23] revocable: Support to define revocable consumer handle on stack
Support a way to define a revocable consumer handle on stack. Under
some circumstances, the user wouldn't like to use dynamic memory
allocation for consumer handles.
This makes the struct revocable no longer opaque.
Signed-off-by: Tzung-Bi Shih <tzungbi@...nel.org>
---
.../driver-api/driver-model/revocable.rst | 5 +-
drivers/base/revocable.c | 60 +++++++++++++------
include/linux/revocable.h | 30 +++++++++-
3 files changed, 74 insertions(+), 21 deletions(-)
diff --git a/Documentation/driver-api/driver-model/revocable.rst b/Documentation/driver-api/driver-model/revocable.rst
index 22a442cc8d7f..fff081dbd296 100644
--- a/Documentation/driver-api/driver-model/revocable.rst
+++ b/Documentation/driver-api/driver-model/revocable.rst
@@ -84,7 +84,7 @@ For Resource Providers
For Resource Consumers
----------------------
-.. kernel-doc:: drivers/base/revocable.c
+.. kernel-doc:: include/linux/revocable.h
:identifiers: revocable
.. kernel-doc:: drivers/base/revocable.c
@@ -93,6 +93,9 @@ For Resource Consumers
.. kernel-doc:: drivers/base/revocable.c
:identifiers: revocable_free
+.. kernel-doc:: include/linux/revocable.h
+ :identifiers: DEFINE_REVOCABLE
+
.. kernel-doc:: drivers/base/revocable.c
:identifiers: revocable_try_access
diff --git a/drivers/base/revocable.c b/drivers/base/revocable.c
index f6cece275aac..93c925252665 100644
--- a/drivers/base/revocable.c
+++ b/drivers/base/revocable.c
@@ -71,16 +71,6 @@ struct revocable_provider {
struct kref kref;
};
-/**
- * struct revocable - A handle for resource consumer.
- * @rp: The pointer of resource provider.
- * @idx: The index for the RCU critical section.
- */
-struct revocable {
- struct revocable_provider *rp;
- int idx;
-};
-
/**
* revocable_provider_alloc() - Allocate struct revocable_provider.
* @res: The pointer of resource.
@@ -170,11 +160,47 @@ struct revocable_provider *devm_revocable_provider_alloc(struct device *dev,
EXPORT_SYMBOL_GPL(devm_revocable_provider_alloc);
/**
- * revocable_alloc() - Allocate struct revocable.
+ * revocable_init() - Initialize struct revocable.
+ * @rev: The pointer of struct revocable.
* @rp: The pointer of resource provider.
*
* This holds a refcount to the resource provider.
*
+ * Don't call this function directly. Use revocable_alloc() or
+ * DEFINE_REVOCABLE().
+ */
+void revocable_init(struct revocable *rev, struct revocable_provider *rp)
+{
+ rev->rp = rp;
+ kref_get(&rp->kref);
+}
+EXPORT_SYMBOL_GPL(revocable_init);
+
+/**
+ * revocable_deinit() - Deinitialize struct revocable.
+ * @rev: The pointer of struct revocable.
+ *
+ * This drops a refcount to the resource provider. If it is the final
+ * reference, revocable_provider_release() will be called to free the struct.
+ *
+ * Don't call this function directly. revocable_free() or DEFINE_REVOCABLE()
+ * should help to do so.
+ */
+void revocable_deinit(struct revocable *rev)
+{
+ struct revocable_provider *rp = rev->rp;
+
+ kref_put(&rp->kref, revocable_provider_release);
+}
+EXPORT_SYMBOL_GPL(revocable_deinit);
+
+/**
+ * revocable_alloc() - Allocate struct revocable.
+ * @rp: The pointer of resource provider.
+ *
+ * Allocate a struct revocable and call revocable_init() to holds a refcount
+ * to the resource provider.
+ *
* Return: The pointer of struct revocable. NULL on errors.
*/
struct revocable *revocable_alloc(struct revocable_provider *rp)
@@ -185,9 +211,7 @@ struct revocable *revocable_alloc(struct revocable_provider *rp)
if (!rev)
return NULL;
- rev->rp = rp;
- kref_get(&rp->kref);
-
+ revocable_init(rev, rp);
return rev;
}
EXPORT_SYMBOL_GPL(revocable_alloc);
@@ -196,14 +220,12 @@ EXPORT_SYMBOL_GPL(revocable_alloc);
* revocable_free() - Free struct revocable.
* @rev: The pointer of struct revocable.
*
- * This drops a refcount to the resource provider. If it is the final
- * reference, revocable_provider_release() will be called to free the struct.
+ * Call revocable_deinit() to drop a refcount to the resource provider and
+ * free the struct revocable.
*/
void revocable_free(struct revocable *rev)
{
- struct revocable_provider *rp = rev->rp;
-
- kref_put(&rp->kref, revocable_provider_release);
+ revocable_deinit(rev);
kfree(rev);
}
EXPORT_SYMBOL_GPL(revocable_free);
diff --git a/include/linux/revocable.h b/include/linux/revocable.h
index 659ba01c58db..89bb1a5c74e4 100644
--- a/include/linux/revocable.h
+++ b/include/linux/revocable.h
@@ -10,19 +10,47 @@
#include <linux/cleanup.h>
struct device;
-struct revocable;
struct revocable_provider;
+/**
+ * struct revocable - A handle for resource consumer.
+ * @rp: The pointer of resource provider.
+ * @idx: The index for the RCU critical section.
+ */
+struct revocable {
+ struct revocable_provider *rp;
+ int idx;
+};
+
struct revocable_provider *revocable_provider_alloc(void *res);
void revocable_provider_revoke(struct revocable_provider *rp);
struct revocable_provider *devm_revocable_provider_alloc(struct device *dev,
void *res);
+void revocable_init(struct revocable *rev, struct revocable_provider *rp);
+void revocable_deinit(struct revocable *rev);
struct revocable *revocable_alloc(struct revocable_provider *rp);
void revocable_free(struct revocable *rev);
void *revocable_try_access(struct revocable *rev) __acquires(&rev->rp->srcu);
void revocable_withdraw_access(struct revocable *rev) __releases(&rev->rp->srcu);
+DEFINE_FREE(define_rev, struct revocable *, revocable_deinit(_T))
+
+#define _DEFINE_REVOCABLE(_rev, _name, _rp) \
+ struct revocable _name; \
+ struct revocable *_rev __free(define_rev) = &_name; \
+ revocable_init(_rev, _rp)
+
+/**
+ * DEFINE_REVOCABLE() - A helper for defining a revocable consumer on stack
+ * @_rev: The variable name to ``struct revocable *``.
+ * @_rp: The provider's ``struct revocable_provider *`` handle.
+ *
+ * The macro declares and defines a revocable consumer handle on stack.
+ */
+#define DEFINE_REVOCABLE(_rev, _rp) \
+ _DEFINE_REVOCABLE(_rev, __UNIQUE_ID(name), _rp)
+
DEFINE_FREE(access_rev, struct revocable *, if (_T) revocable_withdraw_access(_T))
/**
--
2.52.0.457.g6b5491de43-goog
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