[PATCH BlueZ v2] src/shared: add custom CCC callbacks

[PATCH BlueZ v2] src/shared: add custom CCC callbacks

[Prathibha Madugonde]

From: Prathibha Madugonde <prathibha.madugonde@oss.qualcomm.com>

Introduce custom CCC callbacks to allow interception of
client notification subscription changes. This enables
stack-level handling of CCC writes.
---
 src/shared/gatt-db.c | 119 ++++++++++++++++++++++++++++++++++++++++++-
 src/shared/gatt-db.h |   4 ++
 2 files changed, 122 insertions(+), 1 deletion(-)

diff --git a/src/shared/gatt-db.c b/src/shared/gatt-db.c
index d0e149d6f..87cc61cf3 100644
--- a/src/shared/gatt-db.c
+++ b/src/shared/gatt-db.c
@@ -1214,6 +1214,112 @@ gatt_db_service_add_ccc(struct gatt_db_attribute *attrib, uint32_t permissions)
 	return ccc;
 }
 
+static void ccc_custom_read(struct gatt_db_attribute *attrib,
+					unsigned int id, uint16_t offset,
+					uint8_t opcode, struct bt_att *att,
+					void *user_data)
+{
+	struct gatt_db *db = attrib->service->db;
+
+	db->ccc->read_func(attrib, id, offset, opcode, att, db->ccc->user_data);
+}
+
+static void custom_write_result(struct gatt_db_attribute *attr, int err,
+							void *user_data)
+{
+	int *result = user_data;
+
+	*result = err;
+}
+
+static void ccc_custom_write(struct gatt_db_attribute *attrib,
+					unsigned int id, uint16_t offset,
+					const uint8_t *value, size_t len,
+					uint8_t opcode, struct bt_att *att,
+					void *user_data)
+{
+	struct gatt_db_ccc *data = user_data;
+	struct gatt_db *db = attrib->service->db;
+	struct pending_write *p;
+	int err = 0;
+
+	/* Create another pending write to handle results from custom write
+	 * function.
+	 */
+	p = new0(struct pending_write, 1);
+	p->attrib = attrib;
+	p->id = ++attrib->write_id;
+	p->func = custom_write_result;
+	p->user_data = &err;
+
+	queue_push_tail(attrib->pending_writes, p);
+
+	/* Call custom write function first */
+	data->write_func(attrib, p->id, offset, value, len, opcode, att,
+							data->user_data);
+
+	if (err) {
+		gatt_db_attribute_write_result(attrib, id, err);
+		return;
+	}
+
+	/* If custom write function did not return error proceed to call the
+	 * default CCC write function.
+	 */
+	db->ccc->write_func(attrib, id, offset, value, len, opcode, att,
+							db->ccc->user_data);
+}
+
+struct gatt_db_attribute *
+gatt_db_service_add_ccc_custom(struct gatt_db_attribute *attrib,
+				uint32_t permissions,
+				gatt_db_write_t write_func, void *user_data)
+{
+	struct gatt_db *db;
+	struct gatt_db_attribute *ccc;
+	struct gatt_db_attribute *value;
+	uint16_t handle = 0;
+	struct gatt_db_ccc *data;
+
+	if (!attrib || !permissions)
+		return NULL;
+
+	db = attrib->service->db;
+
+	if (!db->ccc)
+		return NULL;
+
+	/* Locate value handle */
+	gatt_db_service_foreach_char(attrib, find_ccc_value, &handle);
+
+	if (!handle)
+		return NULL;
+
+	value = gatt_db_get_attribute(db, handle);
+	if (!value || value->notify_func)
+		return NULL;
+
+	data = new0(struct gatt_db_ccc, 1);
+	data->write_func = write_func;
+	data->user_data = user_data;
+
+	ccc = service_insert_descriptor(attrib->service, 0, &ccc_uuid,
+					permissions,
+					ccc_custom_read,
+					ccc_custom_write,
+					data);
+	if (!ccc) {
+		free(data);
+		return NULL;
+	}
+
+	gatt_db_attribute_set_fixed_length(ccc, 2);
+	ccc->notify_func = db->ccc->notify_func;
+	value->notify_func = db->ccc->notify_func;
+
+	return ccc;
+}
+
 void gatt_db_ccc_register(struct gatt_db *db, gatt_db_read_t read_func,
 				gatt_db_write_t write_func,
 				gatt_db_notify_t notify_func,
@@ -2338,6 +2444,8 @@ bool gatt_db_attribute_notify(struct gatt_db_attribute *attrib,
 					struct bt_att *att)
 {
 	struct gatt_db_attribute *ccc;
+	struct gatt_db *db;
+	void *notify_user_data;
 
 	if (!attrib || !attrib->notify_func)
 		return false;
@@ -2350,7 +2458,16 @@ bool gatt_db_attribute_notify(struct gatt_db_attribute *attrib,
 	if (!ccc)
 		return false;
 
-	attrib->notify_func(attrib, ccc, value, len, att, ccc->user_data);
+	/* For custom CCC descriptors, use the database user_data for
+	 * notify_func. For regular CCC descriptors, use the CCC's user_data.
+	 */
+	db = attrib->service->db;
+	if (ccc->write_func == ccc_custom_write && db && db->ccc)
+		notify_user_data = db->ccc->user_data;
+	else
+		notify_user_data = ccc->user_data;
+
+	attrib->notify_func(attrib, ccc, value, len, att, notify_user_data);
 
 	return true;
 }
diff --git a/src/shared/gatt-db.h b/src/shared/gatt-db.h
index dc2daf7fc..da0600c01 100644
--- a/src/shared/gatt-db.h
+++ b/src/shared/gatt-db.h
@@ -112,6 +112,10 @@ gatt_db_service_insert_descriptor(struct gatt_db_attribute *attrib,
 struct gatt_db_attribute *
 gatt_db_service_add_ccc(struct gatt_db_attribute *attrib, uint32_t permissions);
 
+struct gatt_db_attribute *
+gatt_db_service_add_ccc_custom(struct gatt_db_attribute *attrib,
+				uint32_t permissions,
+				gatt_db_write_t write_func, void *user_data);
 struct gatt_db_attribute *
 gatt_db_insert_included(struct gatt_db *db, uint16_t handle,
 			struct gatt_db_attribute *include);
-- 
2.34.1

RE: [BlueZ,v2] src/shared: add custom CCC callbacks

[bluez.test.bot]

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Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=1085008

---Test result---

Test Summary:
CheckPatch                    PASS      0.48 seconds
GitLint                       PASS      0.28 seconds
BuildEll                      PASS      20.67 seconds
BluezMake                     PASS      648.34 seconds
MakeCheck                     PASS      1.02 seconds
MakeDistcheck                 PASS      249.68 seconds
CheckValgrind                 PASS      225.71 seconds
CheckSmatch                   PASS      352.21 seconds
bluezmakeextell               PASS      183.36 seconds
IncrementalBuild              PASS      640.32 seconds
ScanBuild                     PASS      1032.72 seconds



https://github.com/bluez/bluez/pull/2068

---
Regards,
Linux Bluetooth

Re: [PATCH BlueZ v2] src/shared: add custom CCC callbacks

[patchwork-bot+bluetooth]

Hello:

This patch was applied to bluetooth/bluez.git (master)
by Luiz Augusto von Dentz <luiz.von.dentz@intel.com>:

On Fri, 24 Apr 2026 09:58:30 +0530 you wrote:
> From: Prathibha Madugonde <prathibha.madugonde@oss.qualcomm.com>
> 
> Introduce custom CCC callbacks to allow interception of
> client notification subscription changes. This enables
> stack-level handling of CCC writes.
> ---
>  src/shared/gatt-db.c | 119 ++++++++++++++++++++++++++++++++++++++++++-
>  src/shared/gatt-db.h |   4 ++
>  2 files changed, 122 insertions(+), 1 deletion(-)

Here is the summary with links:
  - [BlueZ,v2] src/shared: add custom CCC callbacks
    https://git.kernel.org/pub/scm/bluetooth/bluez.git/?id=83ddf46ccc06

You are awesome, thank you!
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