driver core: Add flag to autoremove device link on supplier unbind

Add a flag to autoremove the device links on supplier driver
unbind. This obviates the need to explicitly delete the link
in the remove path.
We remove these links only when the supplier's link to its
consumers has gone to DL_STATE_SUPPLIER_UNBIND state.

Signed-off-by: Vivek Gautam <[e-mail]>
Suggested-by: Lukas Wunner <[e-mail]>
Reviewed-by: Ulf Hansson <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

Documentation/driver-api/device_link.rst

···
 This obviates the need to explicitly delete the link in the ``->remove``
 callback or in the error path of the ``->probe`` callback.
 
+Similarly, when the device link is added from supplier's ``->probe`` callback,
+``DL_FLAG_AUTOREMOVE_SUPPLIER`` causes the device link to be automatically
+purged when the supplier fails to probe or later unbinds.
+
 Limitations
 ===========
 

drivers/base/core.c

···
 
 		WARN_ON(link->flags & DL_FLAG_AUTOREMOVE_CONSUMER);
 		WARN_ON(link->status != DL_STATE_SUPPLIER_UNBIND);
+
+		/*
+		 * autoremove the links between this @dev and its consumer
+		 * devices that are not active, i.e. where the link state
+		 * has moved to DL_STATE_SUPPLIER_UNBIND.
+		 */
+		if (link->status == DL_STATE_SUPPLIER_UNBIND &&
+		    link->flags & DL_FLAG_AUTOREMOVE_SUPPLIER)
+			kref_put(&link->kref, __device_link_del);
+
 		WRITE_ONCE(link->status, DL_STATE_DORMANT);
 	}
 

include/linux/device.h

···
  * AUTOREMOVE_CONSUMER: Remove the link automatically on consumer driver unbind.
  * PM_RUNTIME: If set, the runtime PM framework will use this link.
  * RPM_ACTIVE: Run pm_runtime_get_sync() on the supplier during link creation.
+ * AUTOREMOVE_SUPPLIER: Remove the link automatically on supplier driver unbind.
  */
 #define DL_FLAG_STATELESS		BIT(0)
 #define DL_FLAG_AUTOREMOVE_CONSUMER	BIT(1)
 #define DL_FLAG_PM_RUNTIME		BIT(2)
 #define DL_FLAG_RPM_ACTIVE		BIT(3)
+#define DL_FLAG_AUTOREMOVE_SUPPLIER	BIT(4)
 
 /**
  * struct device_link - Device link representation.