[PATCH] Bluetooth: Do not cancel advertising when starting a scan

[PATCH] Bluetooth: Do not cancel advertising when starting a scan

[Manish Mandlik]

From: Dmitry Grinberg <dmitrygr@google.com>

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 <dmitrygr@google.com>
Signed-off-by: Manish Mandlik <mmandlik@google.com>
---

 net/bluetooth/hci_request.c | 17 -----------------
 1 file changed, 17 deletions(-)

diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
index bf83179ab9d19..649e1e5ed446a 100644
--- a/net/bluetooth/hci_request.c
+++ b/net/bluetooth/hci_request.c
@@ -2727,23 +2727,6 @@ static int active_scan(struct hci_request *req, unsigned long opt)
 
 	BT_DBG("%s", hdev->name);
 
-	if (hci_dev_test_flag(hdev, HCI_LE_ADV)) {
-		hci_dev_lock(hdev);
-
-		/* Don't let discovery abort an outgoing connection attempt
-		 * that's using directed advertising.
-		 */
-		if (hci_lookup_le_connect(hdev)) {
-			hci_dev_unlock(hdev);
-			return -EBUSY;
-		}
-
-		cancel_adv_timeout(hdev);
-		hci_dev_unlock(hdev);
-
-		__hci_req_disable_advertising(req);
-	}
-
 	/* If controller is scanning, it means the background scanning is
 	 * running. Thus, we should temporarily stop it in order to set the
 	 * discovery scanning parameters.
-- 
2.25.1.481.gfbce0eb801-goog

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

[Marcel Holtmann]

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 <dmitrygr@google.com>
> Signed-off-by: Manish Mandlik <mmandlik@google.com>
> ---
> 
> 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.

Regards

Marcel

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

[Emil Lenngren]

Hi,

Den ons 18 mars 2020 kl 12:27 skrev Marcel Holtmann <marcel@holtmann.org>:
>
> 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 <dmitrygr@google.com>
> > Signed-off-by: Manish Mandlik <mmandlik@google.com>
> > ---
> >
> > 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

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

[Marcel Holtmann]

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 <dmitrygr@google.com>
>>> Signed-off-by: Manish Mandlik <mmandlik@google.com>
>>> ---
>>> 
>>> 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