tvl-depot/users/flokli/ipu6-softisp/libcamera/0005-libcamera-shared_mem_object-reorganize-the-code-and-.patch

From f94af21adc1889706127d07c5425f44c9cec9a95 Mon Sep 17 00:00:00 2001
From: Andrei Konovalov <andrey.konovalov.ynk@gmail.com>
Date: Mon, 11 Mar 2024 15:15:09 +0100
Subject: [PATCH 05/21] libcamera: shared_mem_object: reorganize the code and
 document the SharedMemObject class

Split the parts which doesn't otherwise depend on the type T or
arguments Args out of the SharedMemObject class into a new
SharedMem class.

Doxygen documentation by Dennis Bonke and Andrei Konovalov.

Reviewed-by: Pavel Machek <pavel@ucw.cz>
Co-developed-by: Dennis Bonke <admin@dennisbonke.com>
Signed-off-by: Dennis Bonke <admin@dennisbonke.com>
Signed-off-by: Andrei Konovalov <andrey.konovalov.ynk@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Milan Zamazal <mzamazal@redhat.com>
---
 .../libcamera/internal/shared_mem_object.h    | 101 ++++++----
 src/libcamera/meson.build                     |   1 +
 src/libcamera/shared_mem_object.cpp           | 190 ++++++++++++++++++
 3 files changed, 253 insertions(+), 39 deletions(-)
 create mode 100644 src/libcamera/shared_mem_object.cpp

diff --git a/include/libcamera/internal/shared_mem_object.h b/include/libcamera/internal/shared_mem_object.h
index 98636b44..43b07c9d 100644
--- a/include/libcamera/internal/shared_mem_object.h
+++ b/include/libcamera/internal/shared_mem_object.h
@@ -6,12 +6,9 @@
  */
 #pragma once
 
-#include <fcntl.h>
 #include <stddef.h>
 #include <string>
 #include <sys/mman.h>
-#include <sys/stat.h>
-#include <unistd.h>
 #include <utility>
 
 #include <libcamera/base/class.h>
@@ -19,58 +16,92 @@
 
 namespace libcamera {
 
+class SharedMem
+{
+public:
+	SharedMem()
+		: mem_(nullptr)
+	{
+	}
+
+	SharedMem(const std::string &name, std::size_t size);
+
+	SharedMem(SharedMem &&rhs)
+	{
+		this->name_ = std::move(rhs.name_);
+		this->fd_ = std::move(rhs.fd_);
+		this->mem_ = rhs.mem_;
+		rhs.mem_ = nullptr;
+	}
+
+	virtual ~SharedMem()
+	{
+		if (mem_)
+			munmap(mem_, size_);
+	}
+
+	/* Make SharedMem non-copyable for now. */
+	LIBCAMERA_DISABLE_COPY(SharedMem)
+
+	SharedMem &operator=(SharedMem &&rhs)
+	{
+		this->name_ = std::move(rhs.name_);
+		this->fd_ = std::move(rhs.fd_);
+		this->mem_ = rhs.mem_;
+		rhs.mem_ = nullptr;
+		return *this;
+	}
+
+	const SharedFD &fd() const
+	{
+		return fd_;
+	}
+
+	void *mem() const
+	{
+		return mem_;
+	}
+
+private:
+	std::string name_;
+	SharedFD fd_;
+	size_t size_;
+protected:
+	void *mem_;
+};
+
 template<class T>
-class SharedMemObject
+class SharedMemObject : public SharedMem
 {
 public:
 	static constexpr std::size_t SIZE = sizeof(T);
 
 	SharedMemObject()
-		: obj_(nullptr)
+		: SharedMem(), obj_(nullptr)
 	{
 	}
 
 	template<class... Args>
 	SharedMemObject(const std::string &name, Args &&...args)
-		: name_(name), obj_(nullptr)
+		: SharedMem(name, SIZE), obj_(nullptr)
 	{
-		void *mem;
-		int ret;
-
-		ret = memfd_create(name_.c_str(), MFD_CLOEXEC);
-		if (ret < 0)
-			return;
-
-		fd_ = SharedFD(std::move(ret));
-		if (!fd_.isValid())
-			return;
-
-		ret = ftruncate(fd_.get(), SIZE);
-		if (ret < 0)
+		if (mem_ == nullptr)
 			return;
 
-		mem = mmap(nullptr, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,
-			   fd_.get(), 0);
-		if (mem == MAP_FAILED)
-			return;
-
-		obj_ = new (mem) T(std::forward<Args>(args)...);
+		obj_ = new (mem_) T(std::forward<Args>(args)...);
 	}
 
 	SharedMemObject(SharedMemObject<T> &&rhs)
+		: SharedMem(std::move(rhs))
 	{
-		this->name_ = std::move(rhs.name_);
-		this->fd_ = std::move(rhs.fd_);
 		this->obj_ = rhs.obj_;
 		rhs.obj_ = nullptr;
 	}
 
 	~SharedMemObject()
 	{
-		if (obj_) {
+		if (obj_)
 			obj_->~T();
-			munmap(obj_, SIZE);
-		}
 	}
 
 	/* Make SharedMemObject non-copyable for now. */
@@ -78,8 +109,7 @@ public:
 
 	SharedMemObject<T> &operator=(SharedMemObject<T> &&rhs)
 	{
-		this->name_ = std::move(rhs.name_);
-		this->fd_ = std::move(rhs.fd_);
+		SharedMem::operator=(std::move(rhs));
 		this->obj_ = rhs.obj_;
 		rhs.obj_ = nullptr;
 		return *this;
@@ -105,19 +135,12 @@ public:
 		return *obj_;
 	}
 
-	const SharedFD &fd() const
-	{
-		return fd_;
-	}
-
 	explicit operator bool() const
 	{
 		return !!obj_;
 	}
 
 private:
-	std::string name_;
-	SharedFD fd_;
 	T *obj_;
 };
 
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index 3c5e43df..94a95ae3 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -41,6 +41,7 @@ libcamera_sources = files([
     'process.cpp',
     'pub_key.cpp',
     'request.cpp',
+    'shared_mem_object.cpp',
     'source_paths.cpp',
     'stream.cpp',
     'sysfs.cpp',
diff --git a/src/libcamera/shared_mem_object.cpp b/src/libcamera/shared_mem_object.cpp
new file mode 100644
index 00000000..44fe74c2
--- /dev/null
+++ b/src/libcamera/shared_mem_object.cpp
@@ -0,0 +1,190 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2023, Raspberry Pi Ltd
+ *
+ * shared_mem_object.cpp - Helper class for shared memory allocations
+ */
+
+#include "libcamera/internal/shared_mem_object.h"
+
+#include <sys/types.h>
+#include <unistd.h>
+
+/**
+ * \file shared_mem_object.cpp
+ * \brief Helper class for shared memory allocations
+ */
+
+namespace libcamera {
+
+/**
+ * \class SharedMem
+ * \brief Helper class for allocating shared memory
+ *
+ * Memory is allocated and exposed as a SharedFD for use across IPC boundaries.
+ *
+ * SharedMem allocates the shared memory of the given size and maps it.
+ * To check that the shared memory was allocated and mapped successfully, one
+ * needs to verify that the pointer to the shared memory returned by SharedMem::mem()
+ * is not nullptr.
+ *
+ * To access the shared memory from another process the SharedFD should be passed
+ * to that process, and then the shared memory should be mapped into that process
+ * address space by calling mmap().
+ *
+ * A single memfd is created for every SharedMem. If there is a need to allocate
+ * a large number of objects in shared memory, these objects should be grouped
+ * together and use the shared memory allocated by a single SharedMem object if
+ * possible. This will help to minimize the number of created memfd's.
+ */
+
+/**
+ * \fn SharedMem::SharedMem(const std::string &name, std::size_t size)
+ * \brief Constructor for the SharedMem
+ * \param[in] name Name of the SharedMem
+ * \param[in] size Size of the shared memory to allocate and map
+ */
+
+/**
+ * \fn SharedMem::SharedMem(SharedMem &&rhs)
+ * \brief Move constructor for SharedMem
+ * \param[in] rhs The object to move
+ */
+
+/**
+ * \fn SharedMem::~SharedMem()
+ * \brief SharedMem destructor
+ *
+ * Unmaps the allocated shared memory. Decrements the shared memory descriptor use
+ * count.
+ */
+
+/**
+ * \fn SharedMem &SharedMem::operator=(SharedMem &&rhs)
+ * \brief Move constructor for SharedMem
+ * \param[in] rhs The object to move
+ */
+
+/**
+ * \fn const SharedFD &SharedMem::fd() const
+ * \brief Gets the file descriptor for the underlying shared memory
+ * \return The file descriptor
+ */
+
+/**
+ * \fn void *SharedMem::mem() const
+ * \brief Gets the pointer to the underlying shared memory
+ * \return The pointer to the shared memory
+ */
+
+SharedMem::SharedMem(const std::string &name, std::size_t size)
+	: name_(name), size_(size), mem_(nullptr)
+{
+	int fd = memfd_create(name_.c_str(), MFD_CLOEXEC);
+	if (fd < 0)
+		return;
+
+	fd_ = SharedFD(std::move(fd));
+	if (!fd_.isValid())
+		return;
+
+	if (ftruncate(fd_.get(), size_) < 0)
+		return;
+
+	mem_ = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED,
+		    fd_.get(), 0);
+	if (mem_ == MAP_FAILED)
+		mem_ = nullptr;
+}
+
+/**
+ * \var SharedMem::mem_
+ * \brief Pointer to the shared memory allocated
+ */
+
+/**
+ * \class SharedMemObject
+ * \brief Helper class for allocating objects in shared memory
+ *
+ * Memory is allocated and exposed as a SharedFD for use across IPC boundaries.
+ *
+ * Given the type of the object to be created in shared memory and the arguments
+ * to pass to this object's constructor, SharedMemObject allocates the shared memory
+ * of the size of the object and constructs the object in this memory. To ensure
+ * that the SharedMemObject was created successfully, one needs to verify that the
+ * overloaded bool() operator returns true. The object created in the shared memory
+ * can be accessed using the SharedMemObject::operator*() indirection operator. Its
+ * members can be accessed with the SharedMemObject::operator->() member of pointer
+ * operator.
+ *
+ * To access the object from another process the SharedFD should be passed to that
+ * process, and the shared memory should be mapped by calling mmap().
+ *
+ * A single memfd is created for every SharedMemObject. If there is a need to allocate
+ * a large number of objects in shared memory, these objects should be grouped into a
+ * single large object to keep the number of created memfd's reasonably small.
+ */
+
+/**
+ * \var SharedMemObject::SIZE
+ * \brief The size of the object that is going to be stored here
+ */
+
+/**
+ * \fn SharedMemObject< T >::SharedMemObject(const std::string &name, Args &&...args)
+ * \brief Constructor for the SharedMemObject
+ * \param[in] name Name of the SharedMemObject
+ * \param[in] args Args to pass to the constructor of the object in shared memory
+ */
+
+/**
+ * \fn SharedMemObject::SharedMemObject(SharedMemObject<T> &&rhs)
+ * \brief Move constructor for SharedMemObject
+ * \param[in] rhs The object to move
+ */
+
+/**
+ * \fn SharedMemObject::~SharedMemObject()
+ * \brief SharedMemObject destructor
+ *
+ * Destroys the object created in the shared memory and then unmaps the shared memory.
+ * Decrements the shared memory descriptor use count.
+ */
+
+/**
+ * \fn SharedMemObject::operator=(SharedMemObject<T> &&rhs)
+ * \brief Operator= for SharedMemObject
+ * \param[in] rhs The SharedMemObject object to take the data from
+ */
+
+/**
+ * \fn SharedMemObject::operator->()
+ * \brief Operator-> for SharedMemObject
+ * \return The pointer to the object
+ */
+
+/**
+ * \fn const T *SharedMemObject::operator->() const
+ * \brief Operator-> for SharedMemObject
+ * \return The pointer to the const object
+ */
+
+/**
+ * \fn SharedMemObject::operator*()
+ * \brief Operator* for SharedMemObject
+ * \return The reference to the object
+ */
+
+/**
+ * \fn const T &SharedMemObject::operator*() const
+ * \brief Operator* for SharedMemObject
+ * \return Const reference to the object
+ */
+
+/**
+ * \fn SharedMemObject::operator bool()
+ * \brief Operator bool() for SharedMemObject
+ * \return True if the object was created OK in the shared memory, false otherwise
+ */
+
+} // namespace libcamera
-- 
2.43.2