driver-core: enable drivers to opt-out of async probe

There are drivers that can not be probed asynchronously. One such group
is platform drivers registered with platform_driver_probe(), which
expects driver's probe routine be discarded after the driver has been
registered and initial binding attempt executed. Also
platform_driver_probe() an error when no devices were bound to the
driver, allowing failing to load such driver module altogether.

Other drivers do not work well with asynchronous probing because of
driver bug or not optimal driver organization.

To allow using such drivers even when user requests asynchronous probing
as default boot strategy, let's allow them to opt out.

Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 7a2fa5dcead7..39292535c74e 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -419,13 +419,19 @@ int driver_probe_device(struct device_driver *drv, struct device *dev)
 
 bool driver_allows_async_probing(struct device_driver *drv)
 {
-	if (drv->probe_type == PROBE_PREFER_ASYNCHRONOUS)
+	switch (drv->probe_type) {
+	case PROBE_PREFER_ASYNCHRONOUS:
 		return true;
 
-	if (drv->owner && drv->owner->async_probe_requested)
-		return true;
+	case PROBE_FORCE_SYNCHRONOUS:
+		return false;
+
+	default:
+		if (drv->owner && drv->owner->async_probe_requested)
+			return true;
 
-	return false;
+		return false;
+	}
 }
 
 struct device_attach_data {