[v2] USB: Fix device driver race

Commit Message

Bastien Nocera July 23, 2020, 9:29 p.m. UTC

When a new device with a specialised device driver is plugged in, the
new driver will be modprobe()'d but the driver core will attach the
"generic" driver to the device.

After that, nothing will trigger a reprobe when the modprobe()'d device
driver has finished initialising, as the device has the "generic"
driver attached to it.

Trigger a reprobe ourselves when new specialised drivers get
registered.

Fixes: 88b7381a939d
Signed-off-by: Bastien Nocera <[e-mail]>
---

Changes since v1:
- Simplified after Alan Stern's comments and some clarifications from
Benjamin Tissoires.

 drivers/usb/core/driver.c | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

+
 /**
  * usb_register_device_driver - register a USB device (not interface)
driver
  * @new_udriver: USB operations for the device driver
@@ -934,13 +953,19 @@ int usb_register_device_driver(struct
usb_device_driver *new_udriver,
 
 	retval = driver_register(&new_udriver->drvwrap.driver);
 
-	if (!retval)
+	if (!retval) {
+		/* Check whether any device could be better served with
+		 * this new driver
+		 */
+		bus_for_each_dev(&usb_bus_type, NULL, NULL,
+				 __usb_bus_reprobe_drivers);
 		pr_info("%s: registered new device driver %s\n",
 			usbcore_name, new_udriver->name);
-	else
+	} else {
 		printk(KERN_ERR "%s: error %d registering device "
 			"	driver %s\n",
 			usbcore_name, retval, new_udriver->name);
+	}
 
 	return retval;
 }

Patch

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index f81606c6a35b..44531910637c 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -905,6 +905,25 @@  static int usb_uevent(struct device *dev, struct
kobj_uevent_env *env)
 	return 0;
 }
 
+static int __usb_bus_reprobe_drivers(struct device *dev, void *data)
+{
+	struct usb_device_driver *udriver = to_usb_device_driver(dev-
>driver);
+	struct usb_device *udev = to_usb_device(dev);
+
+	if (dev->driver) {
+		struct usb_device_driver *udriver =
to_usb_device_driver(dev->driver);
+
+		if (udriver == NULL || udriver == &usb_generic_driver)
{
+			udev->use_generic_driver = false;
+			device_reprobe(dev);
+		}
+	} else {
+		device_reprobe(dev);
+	}
+
+	return 0;
+}