[PATCH] Bluetooth: Add new quirk for broken read key length on ATS2851

[Vinicius Peixoto <nukelet64@xxxxxxxxx>]

The ATS2851 controller erroneously reports support for the "Read
Encryption Key Length" HCI command. This makes it unable to connect
to any devices, since this command is issued by the kernel during the
connection process in response to an "Encryption Change" HCI event.

Add a new quirk (HCI_QUIRK_BROKEN_ENC_KEY_SIZE) to hint that the command
is unsupported, preventing it from interrupting the connection process.

This is the error log from btmon before this patch:

> HCI Event: Encryption Change (0x08) plen 4
        Status: Success (0x00)
        Handle: 2048 Address: ...
        Encryption: Enabled with E0 (0x01)
< HCI Command: Read Encryption Key Size (0x05|0x0008) plen 2
        Handle: 2048 Address: ...
> HCI Event: Command Status (0x0f) plen 4
      Read Encryption Key Size (0x05|0x0008) ncmd 1
        Status: Unknown HCI Command (0x01)

Signed-off-by: Vinicius Peixoto <nukelet64@xxxxxxxxx>
---
 drivers/bluetooth/btusb.c   | 1 +
 include/net/bluetooth/hci.h | 8 ++++++++
 net/bluetooth/hci_event.c   | 3 ++-
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index edfb49bbaa28..96c9318c0874 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -4489,6 +4489,7 @@ static int btusb_probe(struct usb_interface *intf,
 		set_bit(HCI_QUIRK_BROKEN_READ_TRANSMIT_POWER, &hdev->quirks);
 		set_bit(HCI_QUIRK_BROKEN_SET_RPA_TIMEOUT, &hdev->quirks);
 		set_bit(HCI_QUIRK_BROKEN_EXT_SCAN, &hdev->quirks);
+		set_bit(HCI_QUIRK_BROKEN_READ_ENC_KEY_SIZE, &hdev->quirks);
 	}
 
 	if (!reset)
diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 08cb5cb249a4..33b5da0830e2 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -330,6 +330,14 @@ enum {
 	 * during the hdev->setup vendor callback.
 	 */
 	HCI_QUIRK_BROKEN_LE_CODED,
+
+	/*
+	 * When this quirk is set, the HCI_OP_READ_ENC_KEY_SIZE command is
+	 * skipped during an HCI_EV_ENCRYPT_CHANGE event. This is required
+	 * for Actions Semiconductor ATS2851 based controllers, which erroneously
+	 * claim to support it.
+	 */
+	HCI_QUIRK_BROKEN_READ_ENC_KEY_SIZE,
 };
 
 /* HCI device flags */
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index bffd2c7ff608..4ae224824012 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -3641,7 +3641,8 @@ static void hci_encrypt_change_evt(struct hci_dev *hdev, void *data,
 		 * controller really supports it. If it doesn't, assume
 		 * the default size (16).
 		 */
-		if (!(hdev->commands[20] & 0x10)) {
+		if (!(hdev->commands[20] & 0x10) ||
+		    test_bit(HCI_QUIRK_BROKEN_READ_ENC_KEY_SIZE, &hdev->quirks)) {
 			conn->enc_key_size = HCI_LINK_KEY_SIZE;
 			goto notify;
 		}
-- 
2.43.0