driver core: platform: simplify __platform_driver_probe()

__platform_driver_probe() pokes around in some bus and driver private
lists and locks in a way that is not needed at all. The code only wants
to know if a device was bound to the driver that was registered, so walk
all devices on the bus to see if there was a match. If there is not a
match, return an error. This is the same logic as was originally
present, but just done in a simpler and more obvious way that is not a
layering violation.

Cc: "Rafael J. Wysocki" <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/platform.c

···
 	return -ENXIO;
 }
 
+static int is_bound_to_driver(struct device *dev, void *driver)
+{
+	if (dev->driver == driver)
+		return 1;
+	return 0;
+}
+
 /**
  * __platform_driver_probe - register driver for non-hotpluggable device
  * @drv: platform driver structure
···
 	if (retval)
 		return retval;
 
-	/*
-	 * Fixup that section violation, being paranoid about code scanning
-	 * the list of drivers in order to probe new devices.  Check to see
-	 * if the probe was successful, and make sure any forced probes of
-	 * new devices fail.
-	 */
-	spin_lock(&drv->driver.bus->p->klist_drivers.k_lock);
+	/* Force all new probes of this driver to fail */
 	drv->probe = platform_probe_fail;
-	if (list_empty(&drv->driver.p->klist_devices.k_list))
-		retval = -ENODEV;
-	spin_unlock(&drv->driver.bus->p->klist_drivers.k_lock);
 
-	if (retval)
+	/* Walk all platform devices and see if any actually bound to this driver.
+	 * If not, return an error as the device should have done so by now.
+	 */
+	if (!bus_for_each_dev(&platform_bus_type, NULL, &drv->driver, is_bound_to_driver)) {
+		retval = -ENODEV;
 		platform_driver_unregister(drv);
+	}
+
 	return retval;
 }
 EXPORT_SYMBOL_GPL(__platform_driver_probe);