reservation: add headerdoc comments

Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>

drivers/dma-buf/reservation.c

@@ -35,6 +35,17 @@
 #include <linux/reservation.h>
 #include <linux/export.h>
 
+/**
+ * DOC: Reservation Object Overview
+ *
+ * The reservation object provides a mechanism to manage shared and
+ * exclusive fences associated with a buffer.  A reservation object
+ * can have attached one exclusive fence (normally associated with
+ * write operations) or N shared fences (read operations).  The RCU
+ * mechanism is used to protect read access to fences from locked
+ * write-side updates.
+ */
+
 DEFINE_WW_CLASS(reservation_ww_class);
 EXPORT_SYMBOL(reservation_ww_class);
 
@@ -43,9 +54,17 @@ EXPORT_SYMBOL(reservation_seqcount_class);
 
 const char reservation_seqcount_string[] = "reservation_seqcount";
 EXPORT_SYMBOL(reservation_seqcount_string);
-/*
- * Reserve space to add a shared fence to a reservation_object,
- * must be called with obj->lock held.
+
+/**
+ * reservation_object_reserve_shared - Reserve space to add a shared
+ * fence to a reservation_object.
+ * @obj: reservation object
+ *
+ * Should be called before reservation_object_add_shared_fence().  Must
+ * be called with obj->lock held.
+ *
+ * RETURNS
+ * Zero for success, or -errno
  */
 int reservation_object_reserve_shared(struct reservation_object *obj)
 {
@@ -180,7 +199,11 @@ done:
 		fence_put(old_fence);
 }
 
-/*
+/**
+ * reservation_object_add_shared_fence - Add a fence to a shared slot
+ * @obj: the reservation object
+ * @fence: the shared fence to add
+ *
  * Add a fence to a shared slot, obj->lock must be held, and
  * reservation_object_reserve_shared_fence has been called.
  */
@@ -200,6 +223,13 @@ void reservation_object_add_shared_fence(struct reservation_object *obj,
 }
 EXPORT_SYMBOL(reservation_object_add_shared_fence);
 
+/**
+ * reservation_object_add_excl_fence - Add an exclusive fence.
+ * @obj: the reservation object
+ * @fence: the shared fence to add
+ *
+ * Add a fence to the exclusive slot.  The obj->lock must be held.
+ */
 void reservation_object_add_excl_fence(struct reservation_object *obj,
 				       struct fence *fence)
 {
@@ -233,6 +263,18 @@ void reservation_object_add_excl_fence(struct reservation_object *obj,
 }
 EXPORT_SYMBOL(reservation_object_add_excl_fence);
 
+/**
+ * reservation_object_get_fences_rcu - Get an object's shared and exclusive
+ * fences without update side lock held
+ * @obj: the reservation object
+ * @pfence_excl: the returned exclusive fence (or NULL)
+ * @pshared_count: the number of shared fences returned
+ * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
+ * the required size, and must be freed by caller)
+ *
+ * RETURNS
+ * Zero or -errno
+ */
 int reservation_object_get_fences_rcu(struct reservation_object *obj,
 				      struct fence **pfence_excl,
 				      unsigned *pshared_count,
@@ -319,6 +361,18 @@ unlock:
 }
 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
 
+/**
+ * reservation_object_wait_timeout_rcu - Wait on reservation's objects
+ * shared and/or exclusive fences.
+ * @obj: the reservation object
+ * @wait_all: if true, wait on all fences, else wait on just exclusive fence
+ * @intr: if true, do interruptible wait
+ * @timeout: timeout value in jiffies or zero to return immediately
+ *
+ * RETURNS
+ * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
+ * greater than zer on success.
+ */
 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
 					 bool wait_all, bool intr,
 					 unsigned long timeout)
@@ -416,6 +470,16 @@ reservation_object_test_signaled_single(struct fence *passed_fence)
 	return ret;
 }
 
+/**
+ * reservation_object_test_signaled_rcu - Test if a reservation object's
+ * fences have been signaled.
+ * @obj: the reservation object
+ * @test_all: if true, test all fences, otherwise only test the exclusive
+ * fence
+ *
+ * RETURNS
+ * true if all fences signaled, else false
+ */
 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
 					  bool test_all)
 {

include/linux/reservation.h

@@ -49,12 +49,27 @@ extern struct ww_class reservation_ww_class;
 extern struct lock_class_key reservation_seqcount_class;
 extern const char reservation_seqcount_string[];
 
+/**
+ * struct reservation_object_list - a list of shared fences
+ * @rcu: for internal use
+ * @shared_count: table of shared fences
+ * @shared_max: for growing shared fence table
+ * @shared: shared fence table
+ */
 struct reservation_object_list {
 	struct rcu_head rcu;
 	u32 shared_count, shared_max;
 	struct fence __rcu *shared[];
 };
 
+/**
+ * struct reservation_object - a reservation object manages fences for a buffer
+ * @lock: update side lock
+ * @seq: sequence count for managing RCU read-side synchronization
+ * @fence_excl: the exclusive fence, if there is one currently
+ * @fence: list of current shared fences
+ * @staged: staged copy of shared fences for RCU updates
+ */
 struct reservation_object {
 	struct ww_mutex lock;
 	seqcount_t seq;
@@ -68,6 +83,10 @@ struct reservation_object {
 #define reservation_object_assert_held(obj) \
 	lockdep_assert_held(&(obj)->lock.base)
 
+/**
+ * reservation_object_init - initialize a reservation object
+ * @obj: the reservation object
+ */
 static inline void
 reservation_object_init(struct reservation_object *obj)
 {
@@ -79,6 +98,10 @@ reservation_object_init(struct reservation_object *obj)
 	obj->staged = NULL;
 }
 
+/**
+ * reservation_object_fini - destroys a reservation object
+ * @obj: the reservation object
+ */
 static inline void
 reservation_object_fini(struct reservation_object *obj)
 {
@@ -106,6 +129,14 @@ reservation_object_fini(struct reservation_object *obj)
 	ww_mutex_destroy(&obj->lock);
 }
 
+/**
+ * reservation_object_get_list - get the reservation object's
+ * shared fence list, with update-side lock held
+ * @obj: the reservation object
+ *
+ * Returns the shared fence list.  Does NOT take references to
+ * the fence.  The obj->lock must be held.
+ */
 static inline struct reservation_object_list *
 reservation_object_get_list(struct reservation_object *obj)
 {
@@ -113,6 +144,17 @@ reservation_object_get_list(struct reservation_object *obj)
 					 reservation_object_held(obj));
 }
 
+/**
+ * reservation_object_get_excl - get the reservation object's
+ * exclusive fence, with update-side lock held
+ * @obj: the reservation object
+ *
+ * Returns the exclusive fence (if any).  Does NOT take a
+ * reference.  The obj->lock must be held.
+ *
+ * RETURNS
+ * The exclusive fence or NULL
+ */
 static inline struct fence *
 reservation_object_get_excl(struct reservation_object *obj)
 {
@@ -120,6 +162,17 @@ reservation_object_get_excl(struct reservation_object *obj)
 					 reservation_object_held(obj));
 }
 
+/**
+ * reservation_object_get_excl_rcu - get the reservation object's
+ * exclusive fence, without lock held.
+ * @obj: the reservation object
+ *
+ * If there is an exclusive fence, this atomically increments it's
+ * reference count and returns it.
+ *
+ * RETURNS
+ * The exclusive fence or NULL if none
+ */
 static inline struct fence *
 reservation_object_get_excl_rcu(struct reservation_object *obj)
 {