component: add support for releasing match data

The component helper treats the void match data pointer as an opaque
object which needs no further management. When device nodes being
passed, this is not true: the caller should pass its refcount to the
component helper, and there should be a way to drop the refcount when
the matching information is destroyed.

This patch provides a per-match release method in addition to the match
method to solve this issue. Rather than using component_match_add(),
users should use component_match_add_release() which takes an additional
function pointer for releasing this reference.

Signed-off-by: Russell King <[e-mail]>

drivers/base/component.c

···
 
 struct component;
 
+struct component_match_array {
+	void *data;
+	int (*compare)(struct device *, void *);
+	void (*release)(struct device *, void *);
+	struct component *component;
+	bool duplicate;
+};
+
 struct component_match {
 	size_t alloc;
 	size_t num;
-	struct {
-		void *data;
-		int (*fn)(struct device *, void *);
-		struct component *component;
-		bool duplicate;
-	} compare[0];
+	struct component_match_array *compare;
 };
 
 struct master {
···
 	 * any components which are found to this master.
 	 */
 	for (i = 0; i < match->num; i++) {
+		struct component_match_array *mc = &match->compare[i];
 		struct component *c;
 
 		dev_dbg(master->dev, "Looking for component %zu\n", i);
···
 		if (match->compare[i].component)
 			continue;
 
-		c = find_component(master, match->compare[i].fn,
-				   match->compare[i].data);
+		c = find_component(master, mc->compare, mc->data);
 		if (!c) {
 			ret = -ENXIO;
 			break;
···
 	}
 }
 
-static size_t component_match_size(size_t num)
+static void component_match_release(struct device *master,
+	struct component_match *match)
 {
-	return offsetof(struct component_match, compare[num]);
+	unsigned int i;
+
+	for (i = 0; i < match->num; i++) {
+		struct component_match_array *mc = &match->compare[i];
+
+		if (mc->release)
+			mc->release(master, mc->data);
+	}
 }
 
-static struct component_match *component_match_realloc(struct device *dev,
+static void devm_component_match_release(struct device *dev, void *res)
+{
+	component_match_release(dev, res);
+}
+
+static int component_match_realloc(struct device *dev,
 	struct component_match *match, size_t num)
 {
-	struct component_match *new;
+	struct component_match_array *new;
 
-	if (match && match->alloc == num)
-		return match;
+	if (match->alloc == num)
+		return 0;
 
-	new = devm_kmalloc(dev, component_match_size(num), GFP_KERNEL);
+	new = devm_kmalloc_array(dev, num, sizeof(*new), GFP_KERNEL);
 	if (!new)
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 
-	if (match) {
-		memcpy(new, match, component_match_size(min(match->num, num)));
-		devm_kfree(dev, match);
-	} else {
-		new->num = 0;
+	if (match->compare) {
+		memcpy(new, match->compare, sizeof(*new) *
+					    min(match->num, num));
+		devm_kfree(dev, match->compare);
 	}
+	match->compare = new;
+	match->alloc = num;
 
-	new->alloc = num;
-
-	return new;
+	return 0;
 }
 
 /*
- * Add a component to be matched.
+ * Add a component to be matched, with a release function.
  *
  * The match array is first created or extended if necessary.
  */
-void component_match_add(struct device *dev, struct component_match **matchptr,
+void component_match_add_release(struct device *master,
+	struct component_match **matchptr,
+	void (*release)(struct device *, void *),
 	int (*compare)(struct device *, void *), void *compare_data)
 {
 	struct component_match *match = *matchptr;
···
 	if (IS_ERR(match))
 		return;
 
-	if (!match || match->num == match->alloc) {
-		size_t new_size = match ? match->alloc + 16 : 15;
+	if (!match) {
+		match = devres_alloc(devm_component_match_release,
+				     sizeof(*match), GFP_KERNEL);
+		if (!match) {
+			*matchptr = ERR_PTR(-ENOMEM);
+			return;
+		}
 
-		match = component_match_realloc(dev, match, new_size);
+		devres_add(master, match);
 
 		*matchptr = match;
-
-		if (IS_ERR(match))
-			return;
 	}
 
-	match->compare[match->num].fn = compare;
+	if (match->num == match->alloc) {
+		size_t new_size = match ? match->alloc + 16 : 15;
+		int ret;
+
+		ret = component_match_realloc(master, match, new_size);
+		if (ret) {
+			*matchptr = ERR_PTR(ret);
+			return;
+		}
+	}
+
+	match->compare[match->num].compare = compare;
+	match->compare[match->num].release = release;
 	match->compare[match->num].data = compare_data;
 	match->compare[match->num].component = NULL;
 	match->num++;
 }
-EXPORT_SYMBOL(component_match_add);
+EXPORT_SYMBOL(component_match_add_release);
 
 int component_master_add_with_match(struct device *dev,
 	const struct component_master_ops *ops,
···
 	int ret;
 
 	/* Reallocate the match array for its true size */
-	match = component_match_realloc(dev, match, match->num);
-	if (IS_ERR(match))
-		return PTR_ERR(match);
+	ret = component_match_realloc(dev, match, match->num);
+	if (ret)
+		return ret;
 
 	master = kzalloc(sizeof(*master), GFP_KERNEL);
 	if (!master)

include/linux/component.h

···
 #ifndef COMPONENT_H
 #define COMPONENT_H
 
+#include <linux/stddef.h>
+
 struct device;
 
 struct component_ops {
-	int (*bind)(struct device *, struct device *, void *);
-	void (*unbind)(struct device *, struct device *, void *);
+	int (*bind)(struct device *comp, struct device *master,
+		    void *master_data);
+	void (*unbind)(struct device *comp, struct device *master,
+		       void *master_data);
 };
 
 int component_add(struct device *, const struct component_ops *);
 void component_del(struct device *, const struct component_ops *);
 
-int component_bind_all(struct device *, void *);
-void component_unbind_all(struct device *, void *);
+int component_bind_all(struct device *master, void *master_data);
+void component_unbind_all(struct device *master, void *master_data);
 
 struct master;
 
 struct component_master_ops {
-	int (*bind)(struct device *);
-	void (*unbind)(struct device *);
+	int (*bind)(struct device *master);
+	void (*unbind)(struct device *master);
 };
 
 void component_master_del(struct device *,
···
 
 int component_master_add_with_match(struct device *,
 	const struct component_master_ops *, struct component_match *);
-void component_match_add(struct device *, struct component_match **,
+void component_match_add_release(struct device *master,
+	struct component_match **matchptr,
+	void (*release)(struct device *, void *),
 	int (*compare)(struct device *, void *), void *compare_data);
+
+static inline void component_match_add(struct device *master,
+	struct component_match **matchptr,
+	int (*compare)(struct device *, void *), void *compare_data)
+{
+	component_match_add_release(master, matchptr, NULL, compare,
+				    compare_data);
+}
 
 #endif