of: Keep track of populated platform devices

In "Device Tree powered" systems, platform devices are usually massively
populated with of_platform_populate() call, executed at some level of
initcalls, either by generic architecture or by platform-specific code.

There are situations though where certain devices must be created (and
bound with drivers) before all the others. This presents a challenge,
as devices created explicitly would be created again by
of_platform_populate().

This patch tries to solve that issue in a generic way, adding a
"populated" flag for a DT node description. Subsequent
of_platform_populate() will skip such nodes (and its children) in
a similar way to the non-available ones.

This patch also adds of_platform_depopulate() as an operation
complementary to the _populate() one. It removes a platform or an amba
device populated from the Device Tree, together with its all children
(leaving, however, devices without associated of_node untouched)
clearing the "populated" flag on the way.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Grant Likely <grant.likely@linaro.org>

2 files changed, 12 insertions, 0 deletions

diff --git a/include/linux/of.h b/include/linux/of.h
index 3bad8d106e0e..4c50d0b78b89 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -130,6 +130,12 @@ static inline int of_node_check_flag(struct device_node *n, unsigned long flag)
         return test_bit(flag, &n->_flags);
 }
 
+static inline int of_node_test_and_set_flag(struct device_node *n,
+                                            unsigned long flag)
+{
+        return test_and_set_bit(flag, &n->_flags);
+}
+
 static inline void of_node_set_flag(struct device_node *n, unsigned long flag)
 {
         set_bit(flag, &n->_flags);
@@ -197,6 +203,7 @@ static inline unsigned long of_read_ulong(const __be32 *cell, int size)
 /* flag descriptions */
 #define OF_DYNAMIC      1 /* node and properties were allocated via kmalloc */
 #define OF_DETACHED     2 /* node has been detached from the device tree */
+#define OF_POPULATED    3 /* device already created for the node */
 
 #define OF_IS_DYNAMIC(x) test_bit(OF_DYNAMIC, &x->_flags)
 #define OF_MARK_DYNAMIC(x) set_bit(OF_DYNAMIC, &x->_flags)
diff --git a/include/linux/of_platform.h b/include/linux/of_platform.h
index 05cb4a928252..b1010eeaac0d 100644
--- a/include/linux/of_platform.h
+++ b/include/linux/of_platform.h
@@ -72,6 +72,7 @@ extern int of_platform_populate(struct device_node *root,
                                 const struct of_device_id *matches,
                                 const struct of_dev_auxdata *lookup,
                                 struct device *parent);
+extern int of_platform_depopulate(struct device *parent);
 #else
 static inline int of_platform_populate(struct device_node *root,
                                         const struct of_device_id *matches,
@@ -80,6 +81,10 @@ static inline int of_platform_populate(struct device_node *root,
 {
         return -ENODEV;
 }
+static inline int of_platform_depopulate(struct device *parent)
+{
+        return -ENODEV;
+}
 #endif
 
 #endif  /* _LINUX_OF_PLATFORM_H */