libcamera/base: Validate internal headers as private

Headers which must not be exposed as part of the public libcamera API
should include base/private.h.

Any interface which includes the private.h header will only be able to
build if the libcamera_private dependency is used (or the
libcamera_base_private dependency directly).

Build targets which are intended to use the private API's will use the
libcamera_private to handle the automatic definition of the inclusion
guard.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/include/libcamera/base/private.h b/include/libcamera/base/private.h
new file mode 100644
index 00000000..163012bf
--- /dev/null
+++ b/include/libcamera/base/private.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Google Inc.
+ *
+ * private.h - Private Header Validation
+ *
+ * A selection of internal libcamera headers are installed as part
+ * of the libcamera package to allow sharing of a select subset of
+ * internal functionality with IPA module only.
+ *
+ * This functionality is not considered part of the public libcamera
+ * API, and can therefore potentially face ABI instabilities which
+ * should not be exposed to applications. IPA modules however should be
+ * versioned and more closely matched to the libcamera installation.
+ *
+ * Components which include this file can not be included in any file
+ * which forms part of the libcamera API.
+ */
+
+#ifndef LIBCAMERA_BASE_PRIVATE
+#error "Private headers must not be included in the libcamera API"
+#endif