regions: add memory region device support

Provide common code for using memory-backed region devices.
This allows in-memory buffers to act as a region device.

Change-Id: I266cd07bbfa16a427c2b31c512e7c87b77f47718
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/9131
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/include/region.h

@@ -97,4 +97,23 @@ static inline size_t region_sz(const struct region *r)
 	return r->size;
 }
 
+struct mem_region_device {
+	char *base;
+	struct region_device rdev;
+};
+
+/* Iniitalize at runtime a mem_region_device. This would be used when
+ * the base and size are dynamic or can't be known during linking. */
+void mem_region_device_init(struct mem_region_device *mdev, void *base,
+				size_t size);
+
+extern const struct region_device_ops mem_rdev_ops;
+
+/* Statically initialize mem_region_device. */
+#define MEM_REGION_DEV_INIT(base_, size_)				\
+	{								\
+		.base = (void *)(base_),				\
+		.rdev = REGION_DEV_INIT(&mem_rdev_ops, 0, (size_)),	\
+	}
+
 #endif /* _REGION_H_ */

src/lib/region.c

@@ -119,3 +119,45 @@ int rdev_chain(struct region_device *child, const struct region_device *parent,
 
 	return 0;
 }
+
+void mem_region_device_init(struct mem_region_device *mdev, void *base,
+				size_t size)
+{
+	memset(mdev, 0, sizeof(*mdev));
+	mdev->base = base;
+	mdev->rdev.ops = &mem_rdev_ops;
+	mdev->rdev.region.size = size;
+}
+
+static void *mdev_mmap(const struct region_device *rd, size_t offset,
+			size_t size)
+{
+	const struct mem_region_device *mdev;
+
+	mdev = container_of(rd, typeof(*mdev), rdev);
+
+	return &mdev->base[offset];
+}
+
+static int mdev_munmap(const struct region_device *rd, void *mapping)
+{
+	return 0;
+}
+
+static ssize_t mdev_readat(const struct region_device *rd, void *b,
+				size_t offset, size_t size)
+{
+	const struct mem_region_device *mdev;
+
+	mdev = container_of(rd, typeof(*mdev), rdev);
+
+	memcpy(b, &mdev->base[offset], size);
+
+	return size;
+}
+
+const struct region_device_ops mem_rdev_ops = {
+	.mmap = mdev_mmap,
+	.munmap = mdev_munmap,
+	.readat = mdev_readat,
+};