bf5e89478bfd411019cc1af8f1240aeb978777e220e002248fa98a97.patch

From bd76287003539353e7442baadfb2aff8f2827d8c Mon Sep 17 00:00:00 2001
From: Alain Michaud <alainm@chromium.org>
Date: Fri, 9 Apr 2021 15:21:27 +0000
Subject: [PATCH] CHROMIUM: Use link policies to disallow role switches

Some peripherals will attempt to role switch the host device into a
peripheral role mode.  When combined with other peripherals such as mice
and keyboards, this forces the controller to maintain a complicated
topology which results in audio glitches or mouse movement glitches.

The solution implemented by this patch is to leverage the link_policy to
attempt to disallow the peripheral from switching roles once the host
settles into the central role.

This is submitted as a chromium patch to gain some feedback on
improvement before proposing upstream.

Signed-off-by: Alain Michaud <alainm@chromium.org>

BUG=none
TEST=build

Change-Id: I8209b0b1073c0b2d03a2631c64423e67ff96184f
Signed-off-by: Zhengping Jiang <jiangzp@google.com>
Kcr-patch: 2651373bd21928a45d21c88602ed1535423fe062aff4c93be8d231e5.patch
---
 net/bluetooth/hci_conn.c  |  1 +
 net/bluetooth/hci_event.c | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index ebdd7f83eb476c142005417ee68a8f64b78c0ca6..0c44c5d9d6746afe99c4dbf1d0a3879d675d00a3 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -931,6 +931,7 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
 	conn->tx_power = HCI_TX_POWER_INVALID;
 	conn->max_tx_power = HCI_TX_POWER_INVALID;
 	conn->sync_handle = HCI_SYNC_HANDLE_INVALID;
+        conn->link_policy = hdev->link_policy;
 
 	set_bit(HCI_CONN_POWER_SAVE, &conn->flags);
 	conn->disc_timeout = HCI_DISCONN_TIMEOUT;
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index a8b8cfebe0180cce2fb661e8e5f21a79bf7a7656..b44b1cf1431584bf3a4433fc6a83c3c75152faab 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -3183,6 +3183,12 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, void *data,
 	}
 
 	if (!status) {
+		int mask = hdev->link_mode;
+		__u8 flags = 0;
+
+		mask |= hci_proto_connect_ind(hdev, &ev->bdaddr, ev->link_type,
+					      &flags);
+
 		status = hci_conn_set_handle(conn, __le16_to_cpu(ev->handle));
 		if (status)
 			goto done;
@@ -3208,6 +3214,19 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, void *data,
 		if (test_bit(HCI_ENCRYPT, &hdev->flags))
 			set_bit(HCI_CONN_ENCRYPT, &conn->flags);
 
+		/* Attempt to remain in the central role if preferred */
+		if ((conn->mode == HCI_ROLE_MASTER && (mask & HCI_LM_MASTER)) &&
+		    (conn->link_policy & HCI_LP_RSWITCH)) {
+			struct hci_cp_write_link_policy cp;
+
+			conn->link_policy &= ~HCI_LP_RSWITCH;
+
+			cp.handle = ev->handle;
+			cp.policy = conn->link_policy;
+			hci_send_cmd(hdev, HCI_OP_WRITE_LINK_POLICY,
+				     sizeof(cp), &cp);
+		}
+
 		/* "Link key request" completed ahead of "connect request" completes */
 		if (ev->encr_mode == 1 && !test_bit(HCI_CONN_ENCRYPT, &conn->flags) &&
 		    ev->link_type == ACL_LINK) {
-- 
2.44.0.478.gd926399ef9-goog