Given that root hub port peers are already established, external hub peer
ports can be determined by traversing the device topology:
1/ ascend to the parent hub and find the upstream port_dev
2/ walk ->peer to find the peer port
3/ descend to the peer hub via ->child
4/ find the port with the matching port id
Note that this assumes the port labeling scheme required by the
specification [1].
The usb_port_peer_mutex is held when marking hubs as disconnected
(meaning all child ports are invalid for peering) and when the ->child
pointer on a port_dev is marked NULL. Strictly speaking it seems the
latter should be sufficient for protecting collisions with port peering.
However, this still includes the lock around setting hub->disconnected
for extra protection and documentation of the window for when a peer
relationship can be established.
[1]: usb3 3.1 section 10.3.3
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/usb/core/hub.c | 13 +++++++++++--
drivers/usb/core/port.c | 26 ++++++++++++++++++++++++--
2 files changed, 35 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index e5742b888ac8..c463c09c0d37 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1600,7 +1600,13 @@ static void hub_disconnect(struct usb_interface *intf)
struct usb_device *hdev = interface_to_usbdev(intf);
int port1;
- /* Take the hub off the event list and don't let it be added again */
+ /*
+ * 1/ Take the hub off the event list
+ * 2/ Don't let it be added again
+ * 3/ Flush in-progress peering / registration operations when
+ * setting ->disconnected
+ */
+ mutex_lock(&usb_port_peer_mutex);
spin_lock_irq(&hub_event_lock);
if (!list_empty(&hub->event_list)) {
list_del_init(&hub->event_list);
@@ -1608,6 +1614,7 @@ static void hub_disconnect(struct usb_interface *intf)
}
hub->disconnected = 1;
spin_unlock_irq(&hub_event_lock);
+ mutex_unlock(&usb_port_peer_mutex);
/* Disconnect all children and quiesce the hub */
hub->error = 0;
@@ -2085,10 +2092,12 @@ void usb_disconnect(struct usb_device **pdev)
*/
release_devnum(udev);
- /* Avoid races with recursively_mark_NOTATTACHED() */
+ /* Avoid races with recursively_mark_NOTATTACHED(), and peer lookups */
+ mutex_lock(&usb_port_peer_mutex);
spin_lock_irq(&device_state_lock);
*pdev = NULL;
spin_unlock_irq(&device_state_lock);
+ mutex_unlock(&usb_port_peer_mutex);
hub_free_dev(udev);
diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index d8bea408a2f2..8ab5999e2166 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -161,14 +161,14 @@ static struct device_driver usb_port_driver = {
static struct usb_port *find_default_peer(struct usb_hub *hub, int port1)
{
struct usb_device *hdev = hub->hdev;
+ struct usb_device *peer_hdev;
struct usb_port *peer = NULL;
+ struct usb_hub *peer_hub;
if (!hub || hub->disconnected)
return NULL;
if (!hdev->parent) {
- struct usb_hub *peer_hub;
- struct usb_device *peer_hdev;
struct usb_hcd *hcd = bus_to_hcd(hdev->bus);
struct usb_hcd *peer_hcd = hcd->primary_hcd;
@@ -181,6 +181,28 @@ static struct usb_port *find_default_peer(struct usb_hub *hub, int port1)
peer_hub = usb_hub_to_struct_hub(peer_hdev);
if (peer_hub && port1 <= peer_hdev->maxchild)
peer = peer_hub->ports[port1 - 1];
+ } else {
+ struct usb_port *upstream;
+ struct usb_device *parent = hdev->parent;
+ struct usb_hub *parent_hub = usb_hub_to_struct_hub(parent);
+
+ if (!parent_hub || parent_hub->disconnected)
+ return NULL;
+
+ upstream = parent_hub->ports[hdev->portnum - 1];
+ if (!upstream || !upstream->peer)
+ return NULL;
+
+ peer_hdev = upstream->peer->child;
+ if (!peer_hdev)
+ return NULL;
+
+ peer_hub = usb_hub_to_struct_hub(peer_hdev);
+ if (!peer_hub || peer_hub->disconnected
+ || port1 > peer_hdev->maxchild)
+ return NULL;
+
+ peer = peer_hub->ports[port1 - 1];
}
return peer;
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
