regions: add mmap helper device

In order to facilitate platforms which need a buffer cache
for performing boot device operations provide infrastructure
to share the logic in managing the buffer and operations.

Change-Id: I45dd9f213029706ff92a3e5a2c9edd5e8b541e27
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/9132
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/include/region.h

@@ -22,6 +22,7 @@
 
 #include <stdint.h>
 #include <stddef.h>
+#include <mem_pool.h>
 
 /*
  * Region support.
@@ -116,4 +117,20 @@ extern const struct region_device_ops mem_rdev_ops;
 		.rdev = REGION_DEV_INIT(&mem_rdev_ops, 0, (size_)),	\
 	}
 
+struct mmap_helper_region_device {
+	struct mem_pool pool;
+	struct region_device rdev;
+};
+
+#define MMAP_HELPER_REGION_INIT(ops_, offset_, size_) \
+	{								\
+		.rdev = REGION_DEV_INIT((ops_), (offset_), (size_)),	\
+	}
+
+void mmap_helper_device_init(struct mmap_helper_region_device *mdev,
+				void *cache, size_t cache_size);
+
+void *mmap_helper_rdev_mmap(const struct region_device *, size_t, size_t);
+int mmap_helper_rdev_munmap(const struct region_device *, void *);
+
 #endif /* _REGION_H_ */

src/lib/region.c

@@ -161,3 +161,41 @@ const struct region_device_ops mem_rdev_ops = {
 	.munmap = mdev_munmap,
 	.readat = mdev_readat,
 };
+
+void mmap_helper_device_init(struct mmap_helper_region_device *mdev,
+				void *cache, size_t cache_size)
+{
+	mem_pool_init(&mdev->pool, cache, cache_size);
+}
+
+void *mmap_helper_rdev_mmap(const struct region_device *rd, size_t offset,
+				size_t size)
+{
+	struct mmap_helper_region_device *mdev;
+	void *mapping;
+
+	mdev = container_of((void *)rd, typeof(*mdev), rdev);
+
+	mapping = mem_pool_alloc(&mdev->pool, size);
+
+	if (mapping == NULL)
+		return NULL;
+
+	if (rd->ops->readat(rd, mapping, offset, size) != size) {
+		mem_pool_free(&mdev->pool, mapping);
+		return NULL;
+	}
+
+	return mapping;
+}
+
+int mmap_helper_rdev_munmap(const struct region_device *rd, void *mapping)
+{
+	struct mmap_helper_region_device *mdev;
+
+	mdev = container_of((void *)rd, typeof(*mdev), rdev);
+
+	mem_pool_free(&mdev->pool, mapping);
+
+	return 0;
+}