netdev - [PATCH] r8152: limit MAC pass-through to one device

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Date:   Wed, 10 Oct 2018 16:29:33 +0200
From:   Oliver Neukum <oneukum@...e.com>
To:     netdev@...r.kernel.org, davem@...emloft.net, jkohoutek@...e.com,
        mario_limonciello@...l.com
Cc:     Oliver Neukum <oneukum@...e.com>
Subject: [PATCH] r8152: limit MAC pass-through to one device

MAC address having to be unique, a MAC coming from the host
must be used at most once at a time. Hence the users must
be recorded and additional users must fall back to conventional
methods.

Signed-off-by: Oliver Neukum <oneukum@...e.com>
Fixes: 34ee32c9a5696 ("r8152: Add support for setting pass through MAC address on RTL8153-AD")
---
 drivers/net/usb/r8152.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index f1b5201cc320..7345a2258ee4 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -766,6 +766,9 @@ enum tx_csum_stat {
 	TX_CSUM_NONE
 };
 
+/* pass through MACs are per host, hence concurrent use is forbidden */
+static struct r8152 *pass_through_user = NULL;
+
 /* Maximum number of multicast addresses to filter (vs. Rx-all-multicast).
  * The RTL chips use a 64 element hash table based on the Ethernet CRC.
  */
@@ -1221,7 +1224,14 @@ static int set_ethernet_addr(struct r8152 *tp)
 		 * or system doesn't provide valid _SB.AMAC this will be
 		 * be expected to non-zero
 		 */
-		ret = vendor_mac_passthru_addr_read(tp, &sa);
+		if (!pass_through_user) {
+			ret = vendor_mac_passthru_addr_read(tp, &sa);
+			if (ret >= 0)
+				/* we must record the user against concurrent use */
+				pass_through_user = tp;
+		} else {
+			ret = -EBUSY;
+		}
 		if (ret < 0)
 			ret = pla_ocp_read(tp, PLA_BACKUP, 8, sa.sa_data);
 	}
@@ -5304,6 +5314,8 @@ static void rtl8152_disconnect(struct usb_interface *intf)
 		cancel_delayed_work_sync(&tp->hw_phy_work);
 		tp->rtl_ops.unload(tp);
 		free_netdev(tp->netdev);
+		if (pass_through_user == tp)
+			pass_through_user = NULL;
 	}
 }
 
-- 
2.16.4