linux-kernel - [PATCH] ANDROID: usb: core: Send uevent when USB TOPO layer over 6

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Date:   Fri, 26 Feb 2021 17:16:12 +0800
From:   Ricky Niu <rickyniu@...gle.com>
To:     gregkh@...uxfoundation.org, stern@...land.harvard.edu,
        erosca@...adit-jv.com, gustavoars@...nel.org,
        a.darwish@...utronix.de, rickyniu@...gle.com, oneukum@...e.com,
        kyletso@...gle.com
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ANDROID: usb: core: Send uevent when USB TOPO layer over 6

When the topology of the nested hubs are over 6 layers
Send uevent to user space when USB TOPO layer over 6.
Let end user more understand what happened.

Signed-off-by: Ricky Niu <rickyniu@...gle.com>
---
 drivers/usb/core/hub.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 7f71218cc1e5..e5e924526822 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -55,6 +55,10 @@ static DEFINE_SPINLOCK(device_state_lock);
 static struct workqueue_struct *hub_wq;
 static void hub_event(struct work_struct *work);
 
+/* struct to notify userspace of hub events */
+static struct class *hub_class;
+static struct device *hub_device;
+
 /* synchronize hub-port add/remove and peering operations */
 DEFINE_MUTEX(usb_port_peer_mutex);
 
@@ -1764,6 +1768,13 @@ static bool hub_descriptor_is_sane(struct usb_host_interface *desc)
         return true;
 }
 
+static void hub_over_tier(void)
+{
+	char *envp[2] = { "HUB=OVERTIER", NULL };
+
+	kobject_uevent_env(&hub_device->kobj, KOBJ_CHANGE, envp);
+}
+
 static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
 {
 	struct usb_host_interface *desc;
@@ -1831,6 +1842,7 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	if (hdev->level == MAX_TOPO_LEVEL) {
 		dev_err(&intf->dev,
 			"Unsupported bus topology: hub nested too deep\n");
+		hub_over_tier();
 		return -E2BIG;
 	}
 
@@ -5680,6 +5692,13 @@ int usb_hub_init(void)
 		return -1;
 	}
 
+	hub_class = class_create(THIS_MODULE, "usb_hub");
+	if (IS_ERR(hub_class))
+		return PTR_ERR(hub_class);
+
+	hub_device =
+		device_create(hub_class, NULL, MKDEV(0, 0), NULL, "usb_hub");
+
 	/*
 	 * The workqueue needs to be freezable to avoid interfering with
 	 * USB-PERSIST port handover. Otherwise it might see that a full-speed
@@ -5699,6 +5718,9 @@ int usb_hub_init(void)
 
 void usb_hub_cleanup(void)
 {
+	if (!IS_ERR(hub_class))
+		class_destroy(hub_class);
+
 	destroy_workqueue(hub_wq);
 
 	/*
-- 
2.30.1.766.gb4fecdf3b7-goog