driver core: introduce device_set_driver() helper

In preparation to closing a race when reading driver pointer in
dev_uevent() code, instead of setting device->driver pointer directly
introduce device_set_driver() helper.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20250311052417.1846985-2-dmitry.torokhov@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: dtor

drivers/base/base.h

@@ -180,6 +180,12 @@ int driver_add_groups(const struct device_driver *drv, const struct attribute_gr
 void driver_remove_groups(const struct device_driver *drv, const struct attribute_group **groups);
 void device_driver_detach(struct device *dev);
 
+static inline void device_set_driver(struct device *dev, const struct device_driver *drv)
+{
+	// FIXME - this cast should not be needed "soon"
+	dev->driver = (struct device_driver *)drv;
+}
+
 int devres_release_all(struct device *dev);
 void device_block_probing(void);
 void device_unblock_probing(void);

drivers/base/core.c

@@ -3697,7 +3697,7 @@ int device_add(struct device *dev)
 	device_pm_remove(dev);
 	dpm_sysfs_remove(dev);
  DPMError:
-	dev->driver = NULL;
+	device_set_driver(dev, NULL);
 	bus_remove_device(dev);
  BusError:
 	device_remove_attrs(dev);

drivers/base/dd.c

@@ -550,7 +550,7 @@ static void device_unbind_cleanup(struct device *dev)
 	arch_teardown_dma_ops(dev);
 	kfree(dev->dma_range_map);
 	dev->dma_range_map = NULL;
-	dev->driver = NULL;
+	device_set_driver(dev, NULL);
 	dev_set_drvdata(dev, NULL);
 	if (dev->pm_domain && dev->pm_domain->dismiss)
 		dev->pm_domain->dismiss(dev);
@@ -629,8 +629,7 @@ static int really_probe(struct device *dev, const struct device_driver *drv)
 	}
 
 re_probe:
-	// FIXME - this cast should not be needed "soon"
-	dev->driver = (struct device_driver *)drv;
+	device_set_driver(dev, drv);
 
 	/* If using pinctrl, bind pins now before probing */
 	ret = pinctrl_bind_pins(dev);
@@ -1014,7 +1013,7 @@ static int __device_attach(struct device *dev, bool allow_async)
 		if (ret == 0)
 			ret = 1;
 		else {
-			dev->driver = NULL;
+			device_set_driver(dev, NULL);
 			ret = 0;
 		}
 	} else {