When using GATT write without response, it is useful to know how much
data can be sent in a single write. This value is the negotiated MTU
minus 3 bytes.
The D-bus method org.bluez.GattCharacteristic1.AcquireWrite returns the
MTU exactly for this reason. However, when using the alternate API
org.bluez.GattCharacteristic1.WriteValue with the options dictionary
{ "type": "command" }, there is no current way to get the MTU value.
If the value is too large, then the method returns "Failed to initiate
write" [org.bluez.Error.Failed].
This adds an "MTU" property to the org.bluez.Device1 interface that
is emitted in gatt_client_ready_cb() which is after the MTU exchange
has taken place.
Signed-off-by: David Lechner <david@xxxxxxxxxxxxxx>
---
client/main.c | 1 +
doc/device-api.txt | 4 ++++
src/device.c | 24 ++++++++++++++++++++++++
3 files changed, 29 insertions(+)
diff --git a/client/main.c b/client/main.c
index 506602bbd..b12a7da3e 100644
--- a/client/main.c
+++ b/client/main.c
@@ -1754,6 +1754,7 @@ static void cmd_info(int argc, char *argv[])
print_property(proxy, "TxPower");
print_property(proxy, "AdvertisingFlags");
print_property(proxy, "AdvertisingData");
+ print_property(proxy, "MTU");
battery_proxy = find_proxies_by_path(battery_proxies,
g_dbus_proxy_get_path(proxy));
diff --git a/doc/device-api.txt b/doc/device-api.txt
index 4e824d2de..030873821 100644
--- a/doc/device-api.txt
+++ b/doc/device-api.txt
@@ -272,3 +272,7 @@ Properties string Address [readonly]
Example:
<Transport Discovery> <Organization Flags...>
0x26 0x01 0x01...
+
+ uint16 MTU [readonly, optional]
+
+ The exchanged MTU (GATT client only).
diff --git a/src/device.c b/src/device.c
index 26a01612a..898f98da7 100644
--- a/src/device.c
+++ b/src/device.c
@@ -1471,6 +1471,26 @@ static gboolean dev_property_wake_allowed_exist(
return device_get_wake_support(device);
}
+static gboolean
+dev_property_get_mtu(const GDBusPropertyTable *property,
+ DBusMessageIter *iter, void *data)
+{
+ struct btd_device *device = data;
+
+ dbus_uint16_t mtu = bt_gatt_client_get_mtu(device->client);
+ dbus_message_iter_append_basic(iter, DBUS_TYPE_UINT16, &mtu);
+
+ return TRUE;
+}
+
+static gboolean
+dev_property_mtu_exist(const GDBusPropertyTable *property, void *data)
+{
+ struct btd_device *device = data;
+
+ return bt_gatt_client_get_mtu(device->client) != 0;
+}
+
static bool disconnect_all(gpointer user_data)
{
struct btd_device *device = user_data;
@@ -3014,6 +3034,7 @@ static const GDBusPropertyTable device_properties[] = {
{ "WakeAllowed", "b", dev_property_get_wake_allowed,
dev_property_set_wake_allowed,
dev_property_wake_allowed_exist },
+ { "MTU", "q", dev_property_get_mtu, NULL, dev_property_mtu_exist },
{ }
};
@@ -5245,6 +5266,9 @@ static void gatt_client_ready_cb(bool success, uint8_t att_ecode,
return;
}
+ g_dbus_emit_property_changed(dbus_conn, device->path,
+ DEVICE_INTERFACE, "MTU");
+
register_gatt_services(device);
btd_gatt_client_ready(device->client_dbus);
--
2.25.1
