Bluetooth: Send HCI Set Event Mask Page 2 command only when needed

The Broadcom BCM20702 Bluetooth controller in ThinkPad-T530 devices
report support for the Set Event Mask Page 2 command, but actually do
return an error when trying to use it.

  < HCI Command: Read Local Supported Commands (0x04|0x0002) plen 0
  > HCI Event: Command Complete (0x0e) plen 68
       Read Local Supported Commands (0x04|0x0002) ncmd 1
         Status: Success (0x00)
         Commands: 162 entries
           ...
           Set Event Mask Page 2 (Octet 22 - Bit 2)
           ...

  < HCI Command: Set Event Mask Page 2 (0x03|0x0063) plen 8
         Mask: 0x0000000000000000
  > HCI Event: Command Complete (0x0e) plen 4
       Set Event Mask Page 2 (0x03|0x0063) ncmd 1
         Status: Unknown HCI Command (0x01)

Since these controllers do not support any feature that would require
the event mask page 2 to be modified, it is safe to not send this
command at all. The default value is all bits set to zero.

T:  Bus=01 Lev=02 Prnt=02 Port=03 Cnt=03 Dev#=  9 Spd=12   MxCh= 0
D:  Ver= 2.00 Cls=ff(vend.) Sub=01 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=0a5c ProdID=21e6 Rev= 1.12
S:  Manufacturer=Broadcom Corp
S:  Product=BCM20702A0
S:  SerialNumber=F82FA8E8CFC0
C:* #Ifs= 4 Cfg#= 1 Atr=e0 MxPwr=  0mA
I:* If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=01 Prot=01 Driver=btusb
E:  Ad=81(I) Atr=03(Int.) MxPS=  16 Ivl=1ms
E:  Ad=82(I) Atr=02(Bulk) MxPS=  64 Ivl=0ms
E:  Ad=02(O) Atr=02(Bulk) MxPS=  64 Ivl=0ms
I:* If#= 1 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=01 Prot=01 Driver=btusb
E:  Ad=83(I) Atr=01(Isoc) MxPS=   0 Ivl=1ms
E:  Ad=03(O) Atr=01(Isoc) MxPS=   0 Ivl=1ms
I:  If#= 1 Alt= 1 #EPs= 2 Cls=ff(vend.) Sub=01 Prot=01 Driver=btusb
E:  Ad=83(I) Atr=01(Isoc) MxPS=   9 Ivl=1ms
E:  Ad=03(O) Atr=01(Isoc) MxPS=   9 Ivl=1ms
I:  If#= 1 Alt= 2 #EPs= 2 Cls=ff(vend.) Sub=01 Prot=01 Driver=btusb
E:  Ad=83(I) Atr=01(Isoc) MxPS=  17 Ivl=1ms
E:  Ad=03(O) Atr=01(Isoc) MxPS=  17 Ivl=1ms
I:  If#= 1 Alt= 3 #EPs= 2 Cls=ff(vend.) Sub=01 Prot=01 Driver=btusb
E:  Ad=83(I) Atr=01(Isoc) MxPS=  25 Ivl=1ms
E:  Ad=03(O) Atr=01(Isoc) MxPS=  25 Ivl=1ms
I:  If#= 1 Alt= 4 #EPs= 2 Cls=ff(vend.) Sub=01 Prot=01 Driver=btusb
E:  Ad=83(I) Atr=01(Isoc) MxPS=  33 Ivl=1ms
E:  Ad=03(O) Atr=01(Isoc) MxPS=  33 Ivl=1ms
I:  If#= 1 Alt= 5 #EPs= 2 Cls=ff(vend.) Sub=01 Prot=01 Driver=btusb
E:  Ad=83(I) Atr=01(Isoc) MxPS=  49 Ivl=1ms
E:  Ad=03(O) Atr=01(Isoc) MxPS=  49 Ivl=1ms
I:* If#= 2 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=ff Driver=btusb
E:  Ad=84(I) Atr=02(Bulk) MxPS=  32 Ivl=0ms
E:  Ad=04(O) Atr=02(Bulk) MxPS=  32 Ivl=0ms
I:* If#= 3 Alt= 0 #EPs= 0 Cls=fe(app. ) Sub=01 Prot=01 Driver=(none)

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Szymon Janc <szymon.janc@codecoup.pl>

net/bluetooth/hci_core.c

@@ -548,6 +548,7 @@ static void hci_set_event_mask_page_2(struct hci_request *req)
 {
 	struct hci_dev *hdev = req->hdev;
 	u8 events[8] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
+	bool changed = false;
 
 	/* If Connectionless Slave Broadcast master role is supported
 	 * enable all necessary events for it.
@@ -557,6 +558,7 @@ static void hci_set_event_mask_page_2(struct hci_request *req)
 		events[1] |= 0x80;	/* Synchronization Train Complete */
 		events[2] |= 0x10;	/* Slave Page Response Timeout */
 		events[2] |= 0x20;	/* CSB Channel Map Change */
+		changed = true;
 	}
 
 	/* If Connectionless Slave Broadcast slave role is supported
@@ -567,13 +569,24 @@ static void hci_set_event_mask_page_2(struct hci_request *req)
 		events[2] |= 0x02;	/* CSB Receive */
 		events[2] |= 0x04;	/* CSB Timeout */
 		events[2] |= 0x08;	/* Truncated Page Complete */
+		changed = true;
 	}
 
 	/* Enable Authenticated Payload Timeout Expired event if supported */
-	if (lmp_ping_capable(hdev) || hdev->le_features[0] & HCI_LE_PING)
+	if (lmp_ping_capable(hdev) || hdev->le_features[0] & HCI_LE_PING) {
 		events[2] |= 0x80;
+		changed = true;
+	}
 
-	hci_req_add(req, HCI_OP_SET_EVENT_MASK_PAGE_2, sizeof(events), events);
+	/* Some Broadcom based controllers indicate support for Set Event
+	 * Mask Page 2 command, but then actually do not support it. Since
+	 * the default value is all bits set to zero, the command is only
+	 * required if the event mask has to be changed. In case no change
+	 * to the event mask is needed, skip this command.
+	 */
+	if (changed)
+		hci_req_add(req, HCI_OP_SET_EVENT_MASK_PAGE_2,
+			    sizeof(events), events);
 }
 
 static int hci_init3_req(struct hci_request *req, unsigned long opt)