Add read/write callbacks to attribute server

These callbacks will allow profiles to act before an attribute is read
and after it is written, to e.g. update the attribute value to/from an
external source.

Note that by the time the callback is called, the necessary security
checks (attribute permissions, authentication and encryption) were
already performed by the core attribute server.

The callback can optionally return an ATT status code, which will be
sent to the client using an Error Response PDU.

1 files changed, 3 insertions, 0 deletions

diff --git a/attrib/att.h b/attrib/att.h
index 7d9afebe8..9b0b5389a 100644
--- a/attrib/att.h
+++ b/attrib/att.h
@@ -123,6 +123,9 @@ struct attribute {
 	uuid_t uuid;
 	int read_reqs;
 	int write_reqs;
+	uint8_t (*read_cb)(struct attribute *a, gpointer user_data);
+	uint8_t (*write_cb)(struct attribute *a, gpointer user_data);
+	gpointer cb_user_data;
 	int len;
 	uint8_t data[0];
 };