abuf: Provide a way to get the buffer address

In many cases it is useful to get the address of a buffer, e.g. when
booting from it. Add a function to handle this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/abuf.h b/include/abuf.h
index be98ec7..76e314b 100644
--- a/include/abuf.h
+++ b/include/abuf.h
@@ -43,6 +43,14 @@
 }
 
 /**
+ * abuf_addr() - Get the address of a buffer's data
+ *
+ * @abuf: Buffer to check
+ * Return: address of buffer
+ */
+ulong abuf_addr(const struct abuf *abuf);
+
+/**
  * abuf_set() - set the (unallocated) data in a buffer
  *
  * This simply makes the abuf point to the supplied data, which must be live
diff --git a/lib/abuf.c b/lib/abuf.c
index 937c3df..8156177 100644
--- a/lib/abuf.c
+++ b/lib/abuf.c
@@ -26,6 +26,12 @@
 {
 	abuf_set(abuf, map_sysmem(addr, size), size);
 }
+
+ulong abuf_addr(const struct abuf *abuf)
+{
+	return map_to_sysmem(abuf->data);
+}
+
 #else
 /* copied from lib/string.c for convenience */
 static char *memdup(const void *src, size_t len)
diff --git a/test/lib/abuf.c b/test/lib/abuf.c
index 7c0481a..5d61f92 100644
--- a/test/lib/abuf.c
+++ b/test/lib/abuf.c
@@ -46,7 +46,7 @@
 }
 LIB_TEST(lib_test_abuf_set, 0);
 
-/* Test abuf_map_sysmem() */
+/* Test abuf_map_sysmem() and abuf_addr() */
 static int lib_test_abuf_map_sysmem(struct unit_test_state *uts)
 {
 	struct abuf buf;
@@ -60,6 +60,8 @@
 	ut_asserteq(TEST_DATA_LEN, buf.size);
 	ut_asserteq(false, buf.alloced);
 
+	ut_asserteq(addr, abuf_addr(&buf));
+
 	return 0;
 }
 LIB_TEST(lib_test_abuf_map_sysmem, 0);