libcamera: Add IPCPipe

Create a virtual IPCPipe class that models an IPC/RPC system. IPA proxies
and proxy workers will call into the IPCPipe, rather than implementing
the IPC themselves.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/internal/ipc_pipe.h

@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Google Inc.
+ *
+ * ipc_pipe.h - Image Processing Algorithm IPC module for IPA proxies
+ */
+#ifndef __LIBCAMERA_INTERNAL_IPA_IPC_H__
+#define __LIBCAMERA_INTERNAL_IPA_IPC_H__
+
+#include <vector>
+
+#include "libcamera/internal/ipc_unixsocket.h"
+
+#include <libcamera/signal.h>
+
+namespace libcamera {
+
+class IPCMessage
+{
+public:
+	struct Header {
+		uint32_t cmd;
+		uint32_t cookie;
+	};
+
+	IPCMessage();
+	IPCMessage(uint32_t cmd);
+	IPCMessage(const Header &header);
+	IPCMessage(const IPCUnixSocket::Payload &payload);
+
+	IPCUnixSocket::Payload payload() const;
+
+	Header &header() { return header_; }
+	std::vector<uint8_t> &data() { return data_; }
+	std::vector<int32_t> &fds() { return fds_; }
+
+	const Header &header() const { return header_; }
+	const std::vector<uint8_t> &data() const { return data_; }
+	const std::vector<int32_t> &fds() const { return fds_; }
+
+private:
+	Header header_;
+
+	std::vector<uint8_t> data_;
+	std::vector<int32_t> fds_;
+};
+
+class IPCPipe
+{
+public:
+	IPCPipe();
+	virtual ~IPCPipe();
+
+	bool isConnected() const { return connected_; }
+
+	virtual int sendSync(const IPCMessage &in,
+			     IPCMessage *out) = 0;
+
+	virtual int sendAsync(const IPCMessage &data) = 0;
+
+	Signal<const IPCMessage &> recv;
+
+protected:
+	bool connected_;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_INTERNAL_IPA_IPC_H__ */