[libcamera-devel] [PATCH v8 7/9] libcamera: Add IPCPipe

[Paul Elder]

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 at ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

---
Changes in v8:
- fix some docs wording

Changes in v7:
- add an IPCMessage construct that takes just a command code
- remove 'c' from cheader, cdata, and cfds, and just overload them
- implement new sendSync/sendAsync API, so that they only deal with
  IPCMessages
  - so the caller is responsible for populating the command code and the
    sequence number
- cosmetic changes, reword some docs, add some todos

No change in v6

Changes in v5:
- fix style
- rename ipa_ipc.[(cpp)h] to ipc_pipe.[(cpp),h]
- rename IPAIPC to IPCPipe
- add IPCMessage to use in the IPCPipe

Change in v4:
- change snake_case to camelCase
- remove ipaModulePath and ipaProxyWorkerPath from parameters in the
  IPAIPC base contructor
- include signal.h

Changes in v3:
- expand documentation a bit
- move [[maybe_unused]] to after the parameters in the IPAIPC
  constructor, to appease gcc <= 9.1

Changes in v2:
- add documentation
---
 include/libcamera/internal/ipc_pipe.h |  69 ++++++++
 src/libcamera/ipc_pipe.cpp            | 218 ++++++++++++++++++++++++++
 src/libcamera/meson.build             |   1 +
 3 files changed, 288 insertions(+)
 create mode 100644 include/libcamera/internal/ipc_pipe.h
 create mode 100644 src/libcamera/ipc_pipe.cpp

diff --git a/include/libcamera/internal/ipc_pipe.h b/include/libcamera/internal/ipc_pipe.h
new file mode 100644
index 00000000..c9a84b78
--- /dev/null
+++ b/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__ */
diff --git a/src/libcamera/ipc_pipe.cpp b/src/libcamera/ipc_pipe.cpp
new file mode 100644
index 00000000..c402c8d0
--- /dev/null
+++ b/src/libcamera/ipc_pipe.cpp
@@ -0,0 +1,218 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Google Inc.
+ *
+ * ipc_pipe.cpp - Image Processing Algorithm IPC module for IPA proxies
+ */
+
+#include "libcamera/internal/ipc_pipe.h"
+
+#include "libcamera/internal/log.h"
+
+/**
+ * \file ipc_pipe.h
+ * \brief IPC mechanism for IPA isolation
+ */
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(IPCPipe)
+
+/**
+ * \struct IPCMessage::Header
+ * \brief Container for an IPCMessage header
+ *
+ * Holds a cmd code for the IPC message, and a cookie.
+ */
+
+/**
+ * \var IPCMessage::Header::cmd
+ * \brief Type of IPCMessage
+ *
+ * Typically used to carry a command code for an RPC.
+ */
+
+/**
+ * \var IPCMessage::Header::cookie
+ * \brief Cookie to identify the message and a corresponding reply.
+ *
+ * Populated and used by IPCPipe implementations for matching calls with
+ * replies.
+ */
+
+/**
+ * \class IPCMessage
+ * \brief IPC message to be passed through IPC message pipe
+ */
+
+/**
+ * \brief Construct an empty IPCMessage instance
+ */
+IPCMessage::IPCMessage()
+	: header_(Header{ 0, 0 })
+{
+}
+
+/**
+ * \brief Construct an IPCMessage instance with a given command code
+ * \param[in] cmd The command code
+ */
+IPCMessage::IPCMessage(uint32_t cmd)
+	: header_(Header{ cmd, 0 })
+{
+}
+
+/**
+ * \brief Construct an IPCMessage instance with a given header
+ * \param[in] header The header that the constructed IPCMessage will contain
+ */
+IPCMessage::IPCMessage(const Header &header)
+	: header_(header)
+{
+}
+
+/**
+ * \brief Construct an IPCMessage instance from an IPC payload
+ * \param[in] payload The IPCUnixSocket payload to construct from
+ *
+ * This essentially converts an IPCUnixSocket payload into an IPCMessage.
+ * The header is extracted from the payload into the IPCMessage's header field.
+ */
+IPCMessage::IPCMessage(const IPCUnixSocket::Payload &payload)
+{
+	memcpy(&header_, payload.data.data(), sizeof(header_));
+	data_ = std::vector<uint8_t>(payload.data.begin() + sizeof(header_),
+				     payload.data.end());
+	fds_ = payload.fds;
+}
+
+/**
+ * \brief Create an IPCUnixSocket payload from the IPCMessage
+ *
+ * This essentially converts the IPCMessage into an IPCUnixSocket payload.
+ *
+ * \todo Resolve the layering violation (add other converters later?)
+ */
+IPCUnixSocket::Payload IPCMessage::payload() const
+{
+	IPCUnixSocket::Payload payload;
+
+	payload.data.resize(sizeof(Header) + data_.size());
+	payload.fds.reserve(fds_.size());
+
+	memcpy(payload.data.data(), &header_, sizeof(Header));
+
+	/* \todo Make this work without copy */
+	memcpy(payload.data.data() + sizeof(Header), data_.data(), data_.size());
+	payload.fds = fds_;
+
+	return payload;
+}
+
+/**
+ * \fn IPCMessage::header()
+ * \brief Returns a reference to the header
+ */
+
+/**
+ * \fn IPCMessage::data()
+ * \brief Returns a reference to the byte vector containing data
+ */
+
+/**
+ * \fn IPCMessage::fds()
+ * \brief Returns a reference to the vector containing file descriptors
+ */
+
+/**
+ * \fn IPCMessage::header() const
+ * \brief Returns a const reference to the header
+ */
+
+/**
+ * \fn IPCMessage::data() const
+ * \brief Returns a const reference to the byte vector containing data
+ */
+
+/**
+ * \fn IPCMessage::fds() const
+ * \brief Returns a const reference to the vector containing file descriptors
+ */
+
+/**
+ * \class IPCPipe
+ * \brief IPC message pipe for IPA isolation
+ *
+ * Virtual class to model an IPC message pipe for use by IPA proxies for IPA
+ * isolation. sendSync() and sendAsync() must be implemented, and the recvMessage
+ * signal must be emitted whenever new data is available.
+ */
+
+/**
+ * \brief Construct an IPCPipe instance
+ */
+IPCPipe::IPCPipe()
+	: connected_(false)
+{
+}
+
+IPCPipe::~IPCPipe()
+{
+}
+
+/**
+ * \fn IPCPipe::isConnected()
+ * \brief Check if the IPCPipe instance is connected
+ *
+ * An IPCPipe instance is connected if IPC is successfully set up.
+ *
+ * \return True if the IPCPipe is connected, false otherwise
+ */
+
+/**
+ * \fn IPCPipe::sendSync()
+ * \brief Send a message over IPC synchronously
+ * \param[in] in Data to send
+ * \param[in] out IPCMessage instance in which to receive data, if applicable
+ *
+ * This function will not return until a response is received. The event loop
+ * will still continue to execute, however.
+ *
+ * \return Zero on success, negative error code otherwise
+ *
+ * \todo Determine if the event loop should limit the types of messages it
+ * processes, to avoid reintrancy in the caller, and carefully document what
+ * the caller needs to implement to make this safe.
+ */
+
+/**
+ * \fn IPCPipe::sendAsync()
+ * \brief Send a message over IPC asynchronously
+ * \param[in] data Data to send
+ *
+ * This function will return immediately after sending the message.
+ *
+ * \return Zero on success, negative error code otherwise
+ */
+
+/**
+ * \var IPCPipe::recv
+ * \brief Signal to be emitted when a message is received over IPC
+ *
+ * When a message is received over IPC, this signal shall be emitted. Users must
+ * connect to this to receive messages.
+ */
+
+/**
+ * \var IPCPipe::connected_
+ * \brief Flag to indicate if the IPCPipe instance is connected
+ *
+ * An IPCPipe instance is connected if IPC is successfully set up.
+ *
+ * This flag can be read via IPCPipe::isConnected().
+ *
+ * Implementations of the IPCPipe class should set this flag upon successful
+ * connection.
+ */
+
+} /* namespace libcamera */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index c3414ba2..a29fdca2 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -31,6 +31,7 @@ libcamera_sources = files([
     'ipa_manager.cpp',
     'ipa_module.cpp',
     'ipa_proxy.cpp',
+    'ipc_pipe.cpp',
     'ipc_unixsocket.cpp',
     'log.cpp',
     'media_device.cpp',
-- 
2.27.0