[PATCHv2] firmware: arm_scmi: simplify some allocations

Use flexible array members to combine allocations and remove kcalloc
usage.

Add __counted_by where appropriate for extra runtime analysis. Move
counting variable assignment after allocation before any potential array
access.

Also make registered_protocols a static array. No need to use
struct_size when the value is a constant.

Signed-off-by: Rosen Penev <[email protected]>
---
 v2: fix missing struct_size.
 drivers/firmware/arm_scmi/notify.c | 42 ++++++++++++------------------
 1 file changed, 16 insertions(+), 26 deletions(-)

diff --git a/drivers/firmware/arm_scmi/notify.c b/drivers/firmware/arm_scmi/notify.c
index 40ec184eedae..8f69f2f599b2 100644
--- a/drivers/firmware/arm_scmi/notify.c
+++ b/drivers/firmware/arm_scmi/notify.c
@@ -209,11 +209,11 @@ struct scmi_registered_events_desc;
  * @init_work: A work item to perform final initializations of pending handlers
  * @notify_wq: A reference to the allocated Kernel cmwq
  * @pending_mtx: A mutex to protect @pending_events_handlers
+ * @pending_events_handlers: An hashtable containing all pending events'
+ *			     handlers descriptors
  * @registered_protocols: A statically allocated array containing pointers to
  *			  all the registered protocol-level specific information
  *			  related to events' handling
- * @pending_events_handlers: An hashtable containing all pending events'
- *			     handlers descriptors
  *
  * Each platform instance, represented by a handle, has its own instance of
  * the notification subsystem represented by this structure.
@@ -225,8 +225,8 @@ struct scmi_notify_instance {
 	struct workqueue_struct	*notify_wq;
 	/* lock to protect pending_events_handlers */
 	struct mutex		pending_mtx;
-	struct scmi_registered_events_desc	**registered_protocols;
 	DECLARE_HASHTABLE(pending_events_handlers, SCMI_PENDING_HASH_SZ);
+	struct scmi_registered_events_desc	*registered_protocols[SCMI_MAX_PROTO];
 };

 /**
@@ -276,13 +276,13 @@ struct scmi_registered_event;
  * @eh_sz: Size of the pre-allocated buffer @eh
  * @in_flight: A reference to an in flight &struct scmi_registered_event
  * @num_events: Number of events in @registered_events
- * @registered_events: A dynamically allocated array holding all the registered
- *		       events' descriptors, whose fixed-size is determined at
- *		       compile time.
  * @registered_mtx: A mutex to protect @registered_events_handlers
  * @ph: SCMI protocol handle reference
  * @registered_events_handlers: An hashtable containing all events' handlers
  *				descriptors registered for this protocol
+ * @registered_events: A dynamically allocated array holding all the registered
+ *		       events' descriptors, whose fixed-size is determined at
+ *		       compile time.
  *
  * All protocols that register at least one event have their protocol-specific
  * information stored here, together with the embedded allocated events_queue.
@@ -302,11 +302,11 @@ struct scmi_registered_events_desc {
 	size_t				eh_sz;
 	void				*in_flight;
 	int				num_events;
-	struct scmi_registered_event	**registered_events;
 	/* mutex to protect registered_events_handlers */
 	struct mutex			registered_mtx;
 	const struct scmi_protocol_handle	*ph;
 	DECLARE_HASHTABLE(registered_events_handlers, SCMI_REGISTERED_HASH_SZ);
+	struct scmi_registered_event	*registered_events[] __counted_by(num_events);
 };

 /**
@@ -338,9 +338,9 @@ struct scmi_registered_event {
 	void		*report;
 	u32		num_sources;
 	bool		not_supported_by_platform;
-	refcount_t	*sources;
 	/* locking to serialize the access to sources */
 	struct mutex	sources_mtx;
+	refcount_t	sources[] __counted_by(num_sources);
 };

 /**
@@ -706,9 +706,12 @@ scmi_allocate_registered_events_desc(struct scmi_notify_instance *ni,
 	if (WARN_ON(ni->registered_protocols[proto_id]))
 		return ERR_PTR(-EINVAL);

-	pd = devm_kzalloc(ni->handle->dev, sizeof(*pd), GFP_KERNEL);
+	pd = devm_kzalloc(ni->handle->dev, struct_size(pd, registered_events, num_events),
+			GFP_KERNEL);
 	if (!pd)
 		return ERR_PTR(-ENOMEM);
+
+	pd->num_events = num_events;
 	pd->id = proto_id;
 	pd->ops = ops;
 	pd->ni = ni;
@@ -722,12 +725,6 @@ scmi_allocate_registered_events_desc(struct scmi_notify_instance *ni,
 		return ERR_PTR(-ENOMEM);
 	pd->eh_sz = eh_sz;

-	pd->registered_events = devm_kcalloc(ni->handle->dev, num_events,
-					     sizeof(char *), GFP_KERNEL);
-	if (!pd->registered_events)
-		return ERR_PTR(-ENOMEM);
-	pd->num_events = num_events;
-
 	/* Initialize per protocol handlers table */
 	mutex_init(&pd->registered_mtx);
 	hash_init(pd->registered_events_handlers);
@@ -796,18 +793,16 @@ int scmi_register_protocol_events(const struct scmi_handle *handle, u8 proto_id,
 		int id;
 		struct scmi_registered_event *r_evt;

-		r_evt = devm_kzalloc(ni->handle->dev, sizeof(*r_evt),
+		r_evt = devm_kzalloc(ni->handle->dev,
+				     struct_size(r_evt, sources, num_sources),
 				     GFP_KERNEL);
 		if (!r_evt)
 			return -ENOMEM;
+
+		r_evt->num_sources = num_sources;
 		r_evt->proto = pd;
 		r_evt->evt = evt;

-		r_evt->sources = devm_kcalloc(ni->handle->dev, num_sources,
-					      sizeof(refcount_t), GFP_KERNEL);
-		if (!r_evt->sources)
-			return -ENOMEM;
-		r_evt->num_sources = num_sources;
 		mutex_init(&r_evt->sources_mtx);

 		r_evt->report = devm_kzalloc(ni->handle->dev,
@@ -1673,11 +1668,6 @@ int scmi_notification_init(struct scmi_handle *handle)
 	ni->gid = gid;
 	ni->handle = handle;

-	ni->registered_protocols = devm_kcalloc(handle->dev, SCMI_MAX_PROTO,
-						sizeof(char *), GFP_KERNEL);
-	if (!ni->registered_protocols)
-		goto err;
-
 	ni->notify_wq = alloc_workqueue(dev_name(handle->dev),
 					WQ_UNBOUND | WQ_FREEZABLE | WQ_SYSFS,
 					0);
--
2.55.0