[RFC] r8152: pass through needs to be singular

[Oliver Neukum <oneukum@suse.com>]

If multiple devices are connected only one of them
is allowed to get the pass through MAC

Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/net/usb/r8152.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 0f6efaabaa32..15f695398284 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -1193,6 +1193,9 @@ static unsigned int agg_buf_sz = 16384;
 
 #define RTL_LIMITED_TSO_SIZE	(size_to_mtu(agg_buf_sz) - sizeof(struct tx_desc))
 
+static struct r8152 *holder_of_pass_through = NULL;
+static DEFINE_MUTEX(pass_through_lock);
+
 static
 int get_registers(struct r8152 *tp, u16 value, u16 index, u16 size, void *data)
 {
@@ -1587,8 +1590,19 @@ static int __rtl8152_set_mac_address(struct net_device *netdev, void *p,
 	return ret;
 }
 
+static void give_up_pass_through(struct r8152 *tp)
+{
+	mutex_lock(&pass_through_lock);
+	if (tp == holder_of_pass_through)
+		holder_of_pass_through = NULL;
+	mutex_unlock(&pass_through_lock);
+}
+
 static int rtl8152_set_mac_address(struct net_device *netdev, void *p)
 {
+	struct r8152 *tp = netdev_priv(netdev);
+
+	give_up_pass_through(tp);
 	return __rtl8152_set_mac_address(netdev, p, false);
 }
 
@@ -1608,6 +1622,12 @@ static int vendor_mac_passthru_addr_read(struct r8152 *tp, struct sockaddr *sa)
 	acpi_object_type mac_obj_type;
 	int mac_strlen;
 
+	mutex_lock(&pass_through_lock);
+
+	if (!holder_of_pass_through) {
+		ret = -EBUSY;
+		goto failout;
+	}
 	if (tp->lenovo_macpassthru) {
 		mac_obj_name = "\\MACA";
 		mac_obj_type = ACPI_TYPE_STRING;
@@ -1621,7 +1641,8 @@ static int vendor_mac_passthru_addr_read(struct r8152 *tp, struct sockaddr *sa)
 			if ((ocp_data & PASS_THRU_MASK) != 1) {
 				netif_dbg(tp, probe, tp->netdev,
 						"No efuse for RTL8153-AD MAC pass through\n");
-				return -ENODEV;
+				ret = -ENODEV;
+				goto failout;
 			}
 		} else {
 			/* test for RTL8153-BND and RTL8153-BD */
@@ -1629,7 +1650,8 @@ static int vendor_mac_passthru_addr_read(struct r8152 *tp, struct sockaddr *sa)
 			if ((ocp_data & BND_MASK) == 0 && (ocp_data & BD_MASK) == 0) {
 				netif_dbg(tp, probe, tp->netdev,
 						"Invalid variant for MAC pass through\n");
-				return -ENODEV;
+				ret = -ENODEV;
+				goto failout;
 			}
 		}
 
@@ -1641,8 +1663,10 @@ static int vendor_mac_passthru_addr_read(struct r8152 *tp, struct sockaddr *sa)
 	/* returns _AUXMAC_#AABBCCDDEEFF# */
 	status = acpi_evaluate_object(NULL, mac_obj_name, NULL, &buffer);
 	obj = (union acpi_object *)buffer.pointer;
-	if (!ACPI_SUCCESS(status))
-		return -ENODEV;
+	if (!ACPI_SUCCESS(status)) {
+		ret = -ENODEV;
+		goto failout;
+	}
 	if (obj->type != mac_obj_type || obj->string.length != mac_strlen) {
 		netif_warn(tp, probe, tp->netdev,
 			   "Invalid buffer for pass-thru MAC addr: (%d, %d)\n",
@@ -1670,6 +1694,10 @@ static int vendor_mac_passthru_addr_read(struct r8152 *tp, struct sockaddr *sa)
 
 amacout:
 	kfree(obj);
+failout:
+	if (!ret)
+		holder_of_pass_through = tp;
+	mutex_unlock(&pass_through_lock);
 	return ret;
 }
 
@@ -8287,6 +8315,7 @@ static int rtl8152_pre_reset(struct usb_interface *intf)
 		tp->rtl_ops.disable(tp);
 		mutex_unlock(&tp->control);
 	}
+	give_up_pass_through(tp);
 
 	return 0;
 }
@@ -9802,6 +9831,7 @@ static void rtl8152_disconnect(struct usb_interface *intf)
 		cancel_delayed_work_sync(&tp->hw_phy_work);
 		if (tp->rtl_ops.unload)
 			tp->rtl_ops.unload(tp);
+		give_up_pass_through(tp);
 		rtl8152_release_firmware(tp);
 		free_netdev(tp->netdev);
 	}
-- 
2.35.3