driver core: Add device link support for INFERRED flag

This flag can never be added to a device link that already exists and
doesn't have the flag set. It can only be added when a device link is
created for the first time or it can be maintained if the device link
already has the it set.

This flag will be used for marking device links created ONLY by
inferring dependencies from data and NOT from explicit action by device
drivers/frameworks.  This will be useful in the future when we need to
deal with cycles in dependencies inferred from firmware.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20201218031703.3053753-3-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/base/core.c b/drivers/base/core.c
index fe86011..5827dbf 100644 (file)
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -229,7 +229,8 @@ int device_is_dependent(struct device *dev, void *target)
                return ret;
 
        list_for_each_entry(link, &dev->links.consumers, s_node) {
-               if (link->flags == (DL_FLAG_SYNC_STATE_ONLY | DL_FLAG_MANAGED))
+               if ((link->flags & ~DL_FLAG_INFERRED) ==
+                   (DL_FLAG_SYNC_STATE_ONLY | DL_FLAG_MANAGED))
                        continue;
 
                if (link->consumer == target)
@@ -302,7 +303,8 @@ static int device_reorder_to_tail(struct device *dev, void *not_used)
 
        device_for_each_child(dev, NULL, device_reorder_to_tail);
        list_for_each_entry(link, &dev->links.consumers, s_node) {
-               if (link->flags == (DL_FLAG_SYNC_STATE_ONLY | DL_FLAG_MANAGED))
+               if ((link->flags & ~DL_FLAG_INFERRED) ==
+                   (DL_FLAG_SYNC_STATE_ONLY | DL_FLAG_MANAGED))
                        continue;
                device_reorder_to_tail(link->consumer, NULL);
        }
@@ -546,7 +548,8 @@ postcore_initcall(devlink_class_init);
 #define DL_MANAGED_LINK_FLAGS (DL_FLAG_AUTOREMOVE_CONSUMER | \
                               DL_FLAG_AUTOREMOVE_SUPPLIER | \
                               DL_FLAG_AUTOPROBE_CONSUMER  | \
-                              DL_FLAG_SYNC_STATE_ONLY)
+                              DL_FLAG_SYNC_STATE_ONLY | \
+                              DL_FLAG_INFERRED)
 
 #define DL_ADD_VALID_FLAGS (DL_MANAGED_LINK_FLAGS | DL_FLAG_STATELESS | \
                            DL_FLAG_PM_RUNTIME | DL_FLAG_RPM_ACTIVE)
@@ -615,7 +618,7 @@ struct device_link *device_link_add(struct device *consumer,
        if (!consumer || !supplier || flags & ~DL_ADD_VALID_FLAGS ||
            (flags & DL_FLAG_STATELESS && flags & DL_MANAGED_LINK_FLAGS) ||
            (flags & DL_FLAG_SYNC_STATE_ONLY &&
-            flags != DL_FLAG_SYNC_STATE_ONLY) ||
+            (flags & ~DL_FLAG_INFERRED) != DL_FLAG_SYNC_STATE_ONLY) ||
            (flags & DL_FLAG_AUTOPROBE_CONSUMER &&
             flags & (DL_FLAG_AUTOREMOVE_CONSUMER |
                      DL_FLAG_AUTOREMOVE_SUPPLIER)))
@@ -671,6 +674,10 @@ struct device_link *device_link_add(struct device *consumer,
                if (link->consumer != consumer)
                        continue;
 
+               if (link->flags & DL_FLAG_INFERRED &&
+                   !(flags & DL_FLAG_INFERRED))
+                       link->flags &= ~DL_FLAG_INFERRED;
+
                if (flags & DL_FLAG_PM_RUNTIME) {
                        if (!(link->flags & DL_FLAG_PM_RUNTIME)) {
                                pm_runtime_new_link(consumer);

diff --git a/include/linux/device.h b/include/linux/device.h
index 89bb8b8..cb5eb2e 100644 (file)
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -323,6 +323,7 @@ enum device_link_state {
  * AUTOPROBE_CONSUMER: Probe consumer driver automatically after supplier binds.
  * MANAGED: The core tracks presence of supplier/consumer drivers (internal).
  * SYNC_STATE_ONLY: Link only affects sync_state() behavior.
+ * INFERRED: Inferred from data (eg: firmware) and not from driver actions.
  */
 #define DL_FLAG_STATELESS              BIT(0)
 #define DL_FLAG_AUTOREMOVE_CONSUMER    BIT(1)
@@ -332,6 +333,7 @@ enum device_link_state {
 #define DL_FLAG_AUTOPROBE_CONSUMER     BIT(5)
 #define DL_FLAG_MANAGED                        BIT(6)
 #define DL_FLAG_SYNC_STATE_ONLY                BIT(7)
+#define DL_FLAG_INFERRED               BIT(8)
 
 /**
  * enum dl_dev_state - Device driver presence tracking information.