[PATCH v2 4/4] Add SOFT RESERVE resource notification chain

[Nathan Fontenot <nathan.fontenot@xxxxxxx>]

Add a notification chain for SOFT RESERVE resources that are added
to the iomem resource tree when the SOFT_RESERVE_MANAGED config
option is specified.

Update the dax driver to register a notification handler for SOFT
RESERVE resources so that any late added SOFT RESERVES can be
consumed by the driver.

Signed-off-by: Nathan Fontenot <nathan.fontenot@xxxxxxx>
---
 drivers/dax/hmem/hmem.c | 24 +++++++++++++++++++++++-
 include/linux/ioport.h  | 11 +++++++++++
 kernel/resource.c       | 21 +++++++++++++++++++++
 3 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
index 088f4060d4d5..0e6b7558ca3d 100644
--- a/drivers/dax/hmem/hmem.c
+++ b/drivers/dax/hmem/hmem.c
@@ -126,14 +126,36 @@ static int hmem_register_device(const struct resource *res)
 	return rc;
 }
 
+static int dax_hmem_cb(struct notifier_block *nb, unsigned long action,
+		       void *arg)
+{
+	return hmem_register_device((struct resource *)arg);
+}
+
+static struct notifier_block dax_hmem_nb = {
+	.notifier_call = dax_hmem_cb,
+};
+
 static int dax_hmem_platform_probe(struct platform_device *pdev)
 {
+	int rc;
+
 	dax_hmem_pdev = pdev;
-	return walk_hmem_resources(hmem_register_device);
+	rc = walk_hmem_resources(hmem_register_device);
+
+	register_srmem_notifier(&dax_hmem_nb);
+	return rc;
+}
+
+static void dax_hmem_platform_remove(struct platform_device *pdev)
+{
+	dax_hmem_pdev = NULL;
+	unregister_srmem_notifier(&dax_hmem_nb);
 }
 
 static struct platform_driver dax_hmem_platform_driver = {
 	.probe = dax_hmem_platform_probe,
+	.remove = dax_hmem_platform_remove,
 	.driver = {
 		.name = "hmem_platform",
 	},
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 2c95cf0be45e..c173cdd5ab87 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -13,6 +13,7 @@
 #include <linux/bits.h>
 #include <linux/compiler.h>
 #include <linux/minmax.h>
+#include <linux/notifier.h>
 #include <linux/types.h>
 /*
  * Resources are tree-like, allowing
@@ -254,8 +255,18 @@ resource_size_t resource_alignment(struct resource *res);
 void merge_srmem_resources(void);
 extern void release_srmem_region_adjustable(resource_size_t start,
 					    resource_size_t size);
+int register_srmem_notifier(struct notifier_block *nb);
+int unregister_srmem_notifier(struct notifier_block *nb);
 #else
 static inline void merge_srmem_resources(void) { }
+static int register_srmem_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
+static int unregister_srmem_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
 #endif
 
 static inline resource_size_t resource_size(const struct resource *res)
diff --git a/kernel/resource.c b/kernel/resource.c
index 9db420078a3f..3e117e3ba2a5 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1471,6 +1471,26 @@ static void release_region_adjustable(struct resource *parent,
 }
 
 #ifdef CONFIG_SOFT_RESERVED_MANAGED
+
+static RAW_NOTIFIER_HEAD(srmem_chain);
+
+int register_srmem_notifier(struct notifier_block *nb)
+{
+	return raw_notifier_chain_register(&srmem_chain, nb);
+}
+EXPORT_SYMBOL(register_srmem_notifier);
+
+int unregister_srmem_notifier(struct notifier_block *nb)
+{
+	return raw_notifier_chain_unregister(&srmem_chain, nb);
+}
+EXPORT_SYMBOL(unregister_srmem_notifier);
+
+static int srmem_notify(void *v)
+{
+	return raw_notifier_call_chain(&srmem_chain, 0, v);
+}
+
 /**
  * merge_srmem_resources - merge srmem resources into the iomem resource tree
  *
@@ -1497,6 +1517,7 @@ void merge_srmem_resources(void)
 			__insert_resource(&srmem_resource, res);
 
 		write_unlock(&resource_lock);
+		srmem_notify(res);
 	}
 }
 EXPORT_SYMBOL_GPL(merge_srmem_resources);
-- 
2.43.0