On Sat, Apr 01, 2017 at 09:53:03AM +0200, Marcel Holtmann wrote: > > Some things about writing apps and the BLE spec: > > 1) I realize that it is the host that tells the controller the > > random address to use. The controller will NOT automatically use the > > random address from ble_hw_get_static_addr(). That API will be added > > as a convenience so that the app developer does not have to generate > > their own. If the app wants to use this random address it needs to > > tell the controller to use it using LE_Set_Random_Addr. > > > > 2) Regarding the public device address. We have an app called > > bletiny that can set the public device address I think. If the above > > gets approved we are going to remove g_dev_addr from the code; it > > will be kept in the controller and not available globally. The > > Zephyr project is considering adding vendor specific HCI commands, > > one of which is “set public device address”. I think if we go with > > the above approach we should add this vendor specific command and > > that should be the way an app can set the public device address if > > it so chooses. > > The public BD_ADDR needs to be inside the controller before the call > of HCI_Reset. Otherwise all sort of assumptions on HCI break. Until > then the HCI_Read_BD_ADDR has to return 00:00:00:00:00:00 to indicate > the controller has no public address. Switching the BD_ADDR mid-flight > with a backdoor is going to fail in the most funny ways left and > right.
The bletiny app is a sandbox test tool, and it does some things that a more robust application shouldn't do. One such underhanded thing it does is change its own public address whenever the user requests it. It does this by simply overwriting the global public address byte array and hoping for the best. In practice, I've never seen anything funny happen, either to the left or the right :), but this is certainly not guaranteed to work. Also, this won't work at all unless bletiny is running on a combined host-controller, since that is the only occasion in which the host has access to the public address global variable. I don't want to speak for Will, but my guess is he just looked at what existing code accesses the public address global to determine the scope of the proposed API. My understanding from reading his email is that bletiny is doing something sketchy, and that the proposed API won't support this particular use case. Chris
