[PATCH] usb/hcd: Send a uevent signaling that the host controller has died

[Raul E Rangel]

This change will send a CHANGE event to udev with the DEAD environment
variable set when the HC dies. I chose this instead of any of the other
udev events because it's representing a state change in the host
controller. The only other event that might have fit was OFFLINE, but
that seems to be used for hot-removal.

By notifying user space the appropriate policies can be applied.
e.g.,
 * Collect error logs.
 * Notify the user that USB is no longer functional.
 * Perform a graceful reboot.

Signed-off-by: Raul E Rangel <rrangel@xxxxxxxxxxxx>
---

 drivers/usb/core/hcd.c  | 25 +++++++++++++++++++++++++
 include/linux/usb/hcd.h |  1 +
 2 files changed, 26 insertions(+)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 975d7c1288e3..b38ad9ce068b 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -2343,6 +2343,22 @@ int hcd_bus_resume(struct usb_device *rhdev, pm_message_t msg)
 	return status;
 }
 
+
+/**
+ * hcd_died_work - Workqueue routine for root-hub has died.
+ * @hcd: primary host controller for this root hub.
+ *
+ * Do not call with the shared_hcd.
+ * */
+static void hcd_died_work(struct work_struct *work)
+{
+	struct usb_hcd *hcd = container_of(work, struct usb_hcd, died_work);
+
+	/* Notify user space that the host controller has died */
+	kobject_uevent_env(&hcd->self.root_hub->dev.kobj, KOBJ_CHANGE,
+			   (char *[]){ "DEAD=1", NULL });
+}
+
 /* Workqueue routine for root-hub remote wakeup */
 static void hcd_resume_work(struct work_struct *work)
 {
@@ -2488,6 +2504,13 @@ void usb_hc_died (struct usb_hcd *hcd)
 			usb_kick_hub_wq(hcd->self.root_hub);
 		}
 	}
+
+	/* Handle the case where this function gets called with a shared HCD */
+	if (usb_hcd_is_primary_hcd(hcd))
+		schedule_work(&hcd->died_work);
+	else
+		schedule_work(&hcd->primary_hcd->died_work);
+
 	spin_unlock_irqrestore (&hcd_root_hub_lock, flags);
 	/* Make sure that the other roothub is also deallocated. */
 }
@@ -2555,6 +2578,8 @@ struct usb_hcd *__usb_create_hcd(const struct hc_driver *driver,
 	INIT_WORK(&hcd->wakeup_work, hcd_resume_work);
 #endif
 
+	INIT_WORK(&hcd->died_work, hcd_died_work);
+
 	hcd->driver = driver;
 	hcd->speed = driver->flags & HCD_MASK;
 	hcd->product_desc = (driver->product_desc) ? driver->product_desc :
diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index 695931b03684..ae51d5bd1dfc 100644
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -98,6 +98,7 @@ struct usb_hcd {
 #ifdef CONFIG_PM
 	struct work_struct	wakeup_work;	/* for remote wakeup */
 #endif
+	struct work_struct	died_work;	/* for dying */
 
 	/*
 	 * hardware info/state
-- 
2.21.0.392.gf8f6787159e-goog