kent: simplify structure

include/ardix/kent.h

@@ -5,40 +5,21 @@
 #include <ardix/atom.h>
 #include <ardix/types.h>
 
-struct kent;
-
-/**
- * A collection of housekeeping callbacks for kents.
- * This is implemented by every module using kents.
- */
-struct kent_ops {
-	/**
-	 * Destroy this kent and release all allocated resources.
-	 * This is called when the refcount value reaches 0.
-	 *
-	 * @param kent: The kent to be destroyed.
-	 */
-	void (*destroy)(struct kent *kent);
-};
-
 /**
  * struct kent: Kernel Entity
  *
- * This is basically a primitive ripoff of the kobject system in Linux, except
- * there is no representation in a virtual filesystem and it is only really used
- * to keeping track of hierarchial reference counting.
- *
- * The main purpose of kents is to provide a basic common abstraction layer for
- * all modules and submodules of the Ardix kernel.  kents are arranged in a tree
- * structure, and use an atomic reference counter to keep track of when it is
- * safe to destroy them.  This structure is meant to be embedded into bigger
- * structs and then cast out of when a reference to this one is passed to one of
- * the
+ * Kernel entities form a tree structure of reference counters and are meant to
+ * be embedded into structures with dynamic lifetime.  The reference count is
+ * incremented and decremented using the `kent_get()` and `kent_put()` functions
+ * respectively, and when the count reaches zero the `destroy` callback is
+ * invoked.  This callback is responsible for performing any cleanup work
+ * required and releasing resources attached to the structure.  Additionally,
+ * the parent kent's reference count is decremented as well.
  */
 struct kent {
 	struct kent *parent;
 	atom_t refcount;
-	struct kent_ops *operations;
+	void (*destroy)(struct kent *kent);
 };
 
 extern struct kent *kent_root;

kernel/device.c

@@ -17,10 +17,6 @@ static void devices_destroy(struct kent *kent)
 	free(kent);
 }
 
-struct kent_ops devices_kent_ops = {
-	.destroy = &devices_destroy,
-};
-
 /** Initialize the devices subsystem. */
 int devices_init(void)
 {
@@ -32,7 +28,7 @@ int devices_init(void)
 		return -ENOMEM;
 
 	devices_kent->parent = kent_root;
-	devices_kent->operations = &devices_kent_ops;
+	devices_kent->destroy = devices_destroy;
 
 	return kent_init(devices_kent);
 }
@@ -43,17 +39,13 @@ static void device_destroy(struct kent *kent)
 	free(dev);
 }
 
-struct kent_ops device_kent_ops = {
-	.destroy = &device_destroy,
-};
-
 int device_init(struct device *dev)
 {
 	if (devices_kent == NULL)
 		return -ENOENT;
 
-	if (dev->kent.operations == NULL)
-		dev->kent.operations = &device_kent_ops;
+	if (dev->kent.destroy == NULL)
+		dev->kent.destroy = device_destroy;
 	if (dev->kent.parent == NULL)
 		dev->kent.parent = devices_kent;
 

kernel/dma.c

@@ -15,10 +15,6 @@ static void dmabuf_destroy(struct kent *kent)
 	free(buf);
 }
 
-static struct kent_ops dmabuf_kent_ops = {
-	.destroy = &dmabuf_destroy,
-};
-
 struct dmabuf *dmabuf_create(struct device *dev, size_t len)
 {
 	int err = 0;
@@ -27,7 +23,7 @@ struct dmabuf *dmabuf_create(struct device *dev, size_t len)
 		return NULL;
 
 	buf->kent.parent = &dev->kent;
-	buf->kent.operations = &dmabuf_kent_ops;
+	buf->kent.destroy = dmabuf_destroy;
 
 	err = kent_init(&buf->kent);
 	if (err) {

kernel/kent.c

@@ -8,10 +8,6 @@
 #include <errno.h>
 #include <stddef.h>
 
-static struct kent_ops kent_root_ops = {
-	.destroy = NULL,
-};
-
 struct kent _kent_root;
 struct kent *kent_root = NULL;
 
@@ -22,7 +18,7 @@ int kent_root_init(void)
 	kent_root = &_kent_root;
 
 	kent_root->parent = NULL;
-	kent_root->operations = &kent_root_ops;
+	kent_root->destroy = NULL;
 	atom_init(&kent_root->refcount);
 	kent_get(kent_root);
 
@@ -31,7 +27,7 @@ int kent_root_init(void)
 
 int kent_init(struct kent *kent)
 {
-	if (kent->parent == NULL || kent->operations == NULL)
+	if (kent->parent == NULL || kent->destroy == NULL)
 		return -EFAULT;
 	kent_get(kent->parent);
 
@@ -51,7 +47,7 @@ void kent_put(struct kent *kent)
 	struct kent *parent = kent->parent;
 
 	if (atom_put(&kent->refcount) == 0) {
-		kent->operations->destroy(kent);
+		kent->destroy(kent);
 
 		if (parent != NULL)
 			kent_put(parent);

kernel/sched.c

@@ -18,17 +18,13 @@ extern uint32_t _estack;
 static struct task *_sched_tasktab[CONFIG_SCHED_MAXTASK];
 struct task *_sched_current_task;
 
-static void sched_kent_destroy(struct kent *kent)
+static void task_destroy(struct kent *kent)
 {
 	struct task *task = container_of(kent, struct task, kent);
 	_sched_tasktab[task->pid] = NULL;
 	free(task);
 }
 
-static struct kent_ops sched_kent_ops = {
-	.destroy = sched_kent_destroy,
-};
-
 int sched_init(void)
 {
 	int i;
@@ -38,7 +34,7 @@ int sched_init(void)
 		return -ENOMEM;
 
 	_sched_current_task->kent.parent = kent_root;
-	_sched_current_task->kent.operations = &sched_kent_ops;
+	_sched_current_task->kent.destroy = task_destroy;
 	i = kent_init(&_sched_current_task->kent);
 	if (i == 0) {
 		_sched_current_task->sp = &_sstack;
@@ -121,7 +117,7 @@ struct task *sched_fork(struct task *parent)
 		goto err_maxtask;
 
 	child->kent.parent = &parent->kent;
-	child->kent.operations = &sched_kent_ops;
+	child->kent.destroy = task_destroy;
 	if (kent_init(&child->kent) != 0)
 		goto err_kent;