Hi David,
On Mon, Apr 27, 2020 at 8:07 AM David Lechner <david@xxxxxxxxxxxxxx> wrote:
>
> This modifies the GATT client characteristic WriteValue D-Bus method to
> always check that the characteristic supports the requested type of
> write by checking for the corresponding property before attempting to
> write.
>
> Before this change, if the "type" option was used and it was set to
> "reliable" or "request", then BlueZ would attempt the write even if the
> characteristic does not support that write type. On the other hand, if
> "type" was set to "command" or was not specified, the method would
> return a org.bluez.Error.NotSupported error without attempting to write.
>
> After this change, the WriteValue method will consistently return
> org.bluez.Error.NotSupported if the corresponding property flag is not
> set for all types of writes.
> ---
>
> v2 changes:
> - remove extra check of test variable not NULL
> - fix one line over 80 chars
>
> src/gatt-client.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/src/gatt-client.c b/src/gatt-client.c
> index a9bfc2802..f80742fbb 100644
> --- a/src/gatt-client.c
> +++ b/src/gatt-client.c
> @@ -1016,8 +1016,8 @@ static DBusMessage *characteristic_write_value(DBusConnection *conn,
> * - If value is larger than MTU - 3: long-write
> * * "write-without-response" property set -> write command.
> */
> - if ((!type && (chrc->ext_props & BT_GATT_CHRC_EXT_PROP_RELIABLE_WRITE))
> - || (type && !strcasecmp(type, "reliable"))) {
> + if ((!type || !strcasecmp(type, "reliable")) && chrc->ext_props &
> + BT_GATT_CHRC_EXT_PROP_RELIABLE_WRITE) {
> supported = true;
> chrc->write_op = start_long_write(msg, chrc->value_handle, gatt,
> true, value, value_len, offset,
> @@ -1026,8 +1026,8 @@ static DBusMessage *characteristic_write_value(DBusConnection *conn,
> return NULL;
> }
>
> - if ((!type && chrc->props & BT_GATT_CHRC_PROP_WRITE) ||
> - (type && !strcasecmp(type, "request"))) {
> + if ((!type || !strcasecmp(type, "request")) && chrc->props &
> + BT_GATT_CHRC_PROP_WRITE) {
> uint16_t mtu;
>
> supported = true;
> --
> 2.17.1
As far I can remember this is on purpose so the application can
overwrite the type if it needs to disabling the checks on the client
side, though the kernel can still return not supported, so if we want
to change this it will now not be possible to overwrite it anymore.
--
Luiz Augusto von Dentz
