2020-03-18 11:32:46

by Emil Lenngren

[permalink] [raw]
Subject: Re: [PATCH] Bluetooth: Do not cancel advertising when starting a scan

Hi,

Den ons 18 mars 2020 kl 12:27 skrev Marcel Holtmann <[email protected]>:
>
> Hi Manish,
>
> > BlueZ cancels adv when starting a scan, but does not cancel a scan when
> > starting to adv. Neither is required, so this brings both to a
> > consistent state (of not affecting each other). Some very rare (I've
> > never seen one) BT 4.0 chips will fail to do both at once. Even this is
> > ok since the command that will fail will be the second one, and thus the
> > common sense logic of first-come-first-served is preserved for BLE
> > requests.
> >
> > Signed-off-by: Dmitry Grinberg <[email protected]>
> > Signed-off-by: Manish Mandlik <[email protected]>
> > ---
> >
> > net/bluetooth/hci_request.c | 17 -----------------
> > 1 file changed, 17 deletions(-)
>
> patch has been applied to bluetooth-next tree.
>
> If you know the controller that doesn’t support this, can we blacklist that one and just disable advertising (peripheral mode) for that controller.

Can't the "LE Supported States" be inspected instead to figure out
what simultaneous capabilities are supported? It seems a bit rough to
always assume the worst.

/Emil


2020-03-18 11:56:03

by Marcel Holtmann

[permalink] [raw]
Subject: Re: [PATCH] Bluetooth: Do not cancel advertising when starting a scan

Hi Emil,

>>> BlueZ cancels adv when starting a scan, but does not cancel a scan when
>>> starting to adv. Neither is required, so this brings both to a
>>> consistent state (of not affecting each other). Some very rare (I've
>>> never seen one) BT 4.0 chips will fail to do both at once. Even this is
>>> ok since the command that will fail will be the second one, and thus the
>>> common sense logic of first-come-first-served is preserved for BLE
>>> requests.
>>>
>>> Signed-off-by: Dmitry Grinberg <[email protected]>
>>> Signed-off-by: Manish Mandlik <[email protected]>
>>> ---
>>>
>>> net/bluetooth/hci_request.c | 17 -----------------
>>> 1 file changed, 17 deletions(-)
>>
>> patch has been applied to bluetooth-next tree.
>>
>> If you know the controller that doesn’t support this, can we blacklist that one and just disable advertising (peripheral mode) for that controller.
>
> Can't the "LE Supported States" be inspected instead to figure out
> what simultaneous capabilities are supported? It seems a bit rough to
> always assume the worst.

if there are not false-positives, then yes, by all means. However my statement still applies. If a controller can do scanning and advertising at the same time, we should just not indicate support for peripheral mode.

Regards

Marcel