Hi Steve,
On Fri, Mar 23, 2018 at 5:43 PM, Steve Beard <stevieboy10@xxxxxxxxx> wrote:
> Hi all,
>
> During testing of bluez (5.48) with a simple BLE temperature sensor
> beacon device (bluemaestro tempo disc) I have had difficulties
> obtaining the manufacturer data send in the advertisement packet. This
> device sends different manufacturer data in the advertisement than in
> the scan response packet. As far as I can tell this is perfectly
> within the bluetooth specification.
>
> My investigation of the issue has led me to the following methods in
> the bluez source code (src/device.c):
>
> static void add_manufacturer_data(void *data, void *user_data)
> {
> struct eir_msd *msd = data;
> struct btd_device *dev = user_data;
>
> if (!bt_ad_add_manufacturer_data(dev->ad, msd->company, msd->data,
> msd->data_len))
> return;
>
> g_dbus_emit_property_changed(dbus_conn, dev->path,
> DEVICE_INTERFACE, "ManufacturerData");
> }
>
> void device_set_manufacturer_data(struct btd_device *dev, GSList *list,
> bool duplicate)
> {
> if (duplicate)
> bt_ad_clear_manufacturer_data(dev->ad);
>
> g_slist_foreach(list, add_manufacturer_data, dev);
> }
>
> device_set_manufacturer_data iterates over the manufacturer data
> received (in my case there are typically 2 results - one for
> advertisement, the other for the scan response) setting the results on
> the manufacturer data dbus property for the device. My experience is
> that the g_dbus_emit_property_changed results in dbus only notifying
> for the last result (the scan response manufacturer data).
Hmm this may be because the kernel combines the scan report with
advertisement data but it appears it doesn't check if the same data
type is advertised on both.
> Having read through the gdbus/gdbus.h header file I found this comment:
>
> /*
> * Note that when multiple properties for a given object path are changed
> * in the same mainloop iteration, they will be grouped with the last
> * property changed. If this behaviour is undesired, use
> * g_dbus_emit_property_changed_full() with the
> * G_DBUS_PROPERTY_CHANGED_FLAG_FLUSH flag, causing the signal to ignore
> * any grouping.
> */
> void g_dbus_emit_property_changed(DBusConnection *connection,
> const char *path, const char *interface,
> const char *name);
> void g_dbus_emit_property_changed_full(DBusConnection *connection,
> const char *path, const char *interface,
> const char *name,
> GDbusPropertyChangedFlags flags);
>
> This suggests that using g_dbus_emit_property_changes_full with the
> flag G_DBUS_PROPERTY_CHANGED_FLAG_FLUSH will ignore the grouping.
>
> I have tested with the following change to the bluez source code for
> device.c and can confirm that this solves my issue (now receive both
> manufacturer data - tested with bluetoothctl command line tool):
>
> diff --git a/src/device.c b/src/device.c
> index 72f18b3..bc16ed4 100644
> --- a/src/device.c
> +++ b/src/device.c
> @@ -1630,20 +1630,21 @@ void device_add_eir_uuids(struct btd_device
> *dev, GSList *uuids)
> static void add_manufacturer_data(void *data, void *user_data)
> {
> struct eir_msd *msd = data;
> struct btd_device *dev = user_data;
>
> if (!bt_ad_add_manufacturer_data(dev->ad, msd->company, msd->data,
> msd->data_len))
> return;
>
> - g_dbus_emit_property_changed(dbus_conn, dev->path,
> - DEVICE_INTERFACE, "ManufacturerData");
> + g_dbus_emit_property_changed_full(dbus_conn, dev->path,
> + DEVICE_INTERFACE, "ManufacturerData",
> + G_DBUS_PROPERTY_CHANGED_FLAG_FLUSH);
> }
>
> void device_set_manufacturer_data(struct btd_device *dev, GSList *list,
> bool duplicate)
> {
> if (duplicate)
> bt_ad_clear_manufacturer_data(dev->ad);
>
> g_slist_foreach(list, add_manufacturer_data, dev);
>
> I therefore ask that this issue described be considered for fixing in
> future release and that the proposed change be considered for merging
> into the source.
While we could do something like that I think it we need to detect if
there is really 2 different reports or not otherwise this could turn
to be very spammy when DuplicateData filter is set.
> Kind regards,
>
> Steven Beard
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--
Luiz Augusto von Dentz
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