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of/overlay: add of overlay notifications

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This patch add of overlay notifications.

When DT overlays are being added, some drivers/subsystems
need to see device tree overlays before the changes go into
the live tree.

This is distinct from reconfig notifiers that are
post-apply or post-remove and which issue very granular
notifications without providing access to the context
of a whole overlay.

The following 4 notificatons are issued:
  OF_OVERLAY_PRE_APPLY
  OF_OVERLAY_POST_APPLY
  OF_OVERLAY_PRE_REMOVE
  OF_OVERLAY_POST_REMOVE

In the case of pre-apply notification, if the notifier
returns error, the overlay will be rejected.

This patch exports two functions for registering/unregistering
notifications:
  of_overlay_notifier_register(struct notifier_block *nb)
  of_overlay_notifier_unregister(struct notifier_block *nb)

The of_mutex is held during these notifications. The
notification data includes pointers to the overlay target
and the overlay:

struct of_overlay_notify_data {
       struct device_node *overlay;
       struct device_node *target;
};

Signed-off-by: Alan Tull <atull@opensource.altera.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Moritz Fischer <moritz.fischer@ettus.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alan Tull
2016-11-01 14:14:22 -05:00
committed by Greg Kroah-Hartman
parent c1eac0d034
commit 39a842e22c
2 changed files with 71 additions and 1 deletions
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25
include/linux/of.h
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@@ -1266,6 +1266,18 @@ static inline bool of_device_is_system_power_controller(const struct device_node
* Overlay support
*/
enum of_overlay_notify_action {
OF_OVERLAY_PRE_APPLY,
OF_OVERLAY_POST_APPLY,
OF_OVERLAY_PRE_REMOVE,
OF_OVERLAY_POST_REMOVE,
};
struct of_overlay_notify_data {
struct device_node *overlay;
struct device_node *target;
};
#ifdef CONFIG_OF_OVERLAY
/* ID based overlays; the API for external users */
@@ -1273,6 +1285,9 @@ int of_overlay_create(struct device_node *tree);
int of_overlay_destroy(int id);
int of_overlay_destroy_all(void);
int of_overlay_notifier_register(struct notifier_block *nb);
int of_overlay_notifier_unregister(struct notifier_block *nb);
#else
static inline int of_overlay_create(struct device_node *tree)
@@ -1290,6 +1305,16 @@ static inline int of_overlay_destroy_all(void)
return -ENOTSUPP;
}
static inline int of_overlay_notifier_register(struct notifier_block *nb)
{
return 0;
}
static inline int of_overlay_notifier_unregister(struct notifier_block *nb)
{
return 0;
}
#endif
#endif /* _LINUX_OF_H */