[Pdbg] [RFC 04/12] libpdbg: Introduce a backend field

[Alistair Popple]

It is useful to be able to override a particular targets access
methods with methods specific to a specific runtime environment. This
patch introduces a field to every target which can be used for this
purpose without affecting the current behaviour.

Signed-off-by: Alistair Popple <alistair at popple.id.au>
---
 libpdbg/target.c | 12 +++++++++---
 libpdbg/target.h |  1 +
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/libpdbg/target.c b/libpdbg/target.c
index 61353bc..e822d70 100644
--- a/libpdbg/target.c
+++ b/libpdbg/target.c
@@ -14,8 +14,8 @@
 struct list_head empty_list = LIST_HEAD_INIT(empty_list);
 struct list_head target_classes = LIST_HEAD_INIT(target_classes);
 
-/* Work out the address to access based on the current target and
- * final class name */
+/* Work out the target and address to call call access methods on
+ * based on the current target and final class name */
 static struct pdbg_target *get_class_target_addr(struct pdbg_target *target, const char *name, uint64_t *addr)
 {
 	/* Check class */
@@ -34,7 +34,13 @@ static struct pdbg_target *get_class_target_addr(struct pdbg_target *target, con
 		assert(target != pdbg_target_root());
 	}
 
-	return target;
+	if (target->backend) {
+		/* The backend must implement the same interfaces */
+		assert(!strcmp(target->class, target->backend->class));
+		return target->backend;
+	} else {
+		return target;
+	}
 }
 
 struct pdbg_target *pdbg_address_absolute(struct pdbg_target *target, uint64_t *addr)
diff --git a/libpdbg/target.h b/libpdbg/target.h
index 9394447..2c76bf9 100644
--- a/libpdbg/target.h
+++ b/libpdbg/target.h
@@ -46,6 +46,7 @@ struct pdbg_target {
 	struct list_head properties;
 	struct list_head children;
 	struct pdbg_target *parent;
+	struct pdbg_target *backend;
 	u32 phandle;
 	bool probed;
 	struct list_node class_link;
-- 
2.20.1