[PATCH v7 1/5] Documentation: Add Thread safety page

[Daniel Scally]

Move the section of the Thread support page dealing with thread safety
to a dedicated .dox file at Documentation/. This is done to support the
splitting of the Documentation into a public and internal version. With
a separate page, references can be made to thread safety without having
to include the Thread class in the doxygen run. Some sections of the new
page are still specific to internal implementations and so are hidden
with the \internal flag and an internal section which is conditionally
included. For now, hardcode it to be included in the Doxyfile.

Signed-off-by: Daniel Scally <dan.scally at ideasonboard.com>
---
Changes since v6:

Conditionally included any reference to thread-bound behind either the \internal
directive or and internal section.

Changes since v5:

- Much of the content that dealt with internal implementation was moved
  back to its place against the Thread class. The thread safety section
  is retained in a separate page, with a single reference to the main
  thread support page who's display is conditional on the doxygen
  INTERNAL_DOCS directive.

Given the scope of the changes, I dropped the R-b tags the patch had
accumulated

Changes since v1:

- New patch

 Documentation/Doxyfile.in       |  5 +++-
 Documentation/thread-safety.dox | 48 +++++++++++++++++++++++++++++++++
 src/libcamera/base/thread.cpp   | 36 -------------------------
 3 files changed, 52 insertions(+), 37 deletions(-)
 create mode 100644 Documentation/thread-safety.dox

diff --git a/Documentation/Doxyfile.in b/Documentation/Doxyfile.in
index 62e63968..203f8e67 100644
--- a/Documentation/Doxyfile.in
+++ b/Documentation/Doxyfile.in
@@ -17,13 +17,15 @@ EXTENSION_MAPPING      = h=C++
 
 TOC_INCLUDE_HEADINGS   = 0
 
+ENABLED_SECTIONS       = internal
 INTERNAL_DOCS          = YES
 CASE_SENSE_NAMES       = YES
 
 QUIET                  = YES
 WARN_AS_ERROR          = @WARN_AS_ERROR@
 
-INPUT                  = "@TOP_SRCDIR@/include/libcamera" \
+INPUT                  = "@TOP_SRCDIR@/Documentation" \
+                         "@TOP_SRCDIR@/include/libcamera" \
                          "@TOP_SRCDIR@/src/ipa/ipu3" \
                          "@TOP_SRCDIR@/src/ipa/libipa" \
                          "@TOP_SRCDIR@/src/libcamera" \
@@ -32,6 +34,7 @@ INPUT                  = "@TOP_SRCDIR@/include/libcamera" \
 
 FILE_PATTERNS          = *.c \
                          *.cpp \
+                         *.dox \
                          *.h
 
 RECURSIVE              = YES
diff --git a/Documentation/thread-safety.dox b/Documentation/thread-safety.dox
new file mode 100644
index 00000000..1a610035
--- /dev/null
+++ b/Documentation/thread-safety.dox
@@ -0,0 +1,48 @@
+/**
+ * \page thread-safety Reentrancy and Thread-Safety
+ *
+ * Through the documentation, several terms are used to define how classes and
+ * their member functions can be used from multiple threads.
+ *
+ * - A **reentrant** function may be called simultaneously from multiple
+ *   threads if and only if each invocation uses a different instance of the
+ *   class. This is the default for all member functions not explictly marked
+ *   otherwise.
+ *
+ * - \anchor thread-safe A **thread-safe** function may be called
+ *   simultaneously from multiple threads on the same instance of a class. A
+ *   thread-safe function is thus reentrant. Thread-safe functions may also be
+ *   called simultaneously with any other reentrant function of the same class
+ *   on the same instance.
+ *
+ * \internal
+ * - \anchor thread-bound A **thread-bound** function may be called only from
+ *   the thread that the class instances lives in (see section \ref
+ *   thread-objects). For instances of classes that do not derive from the
+ *   Object class, this is the thread in which the instance was created. A
+ *   thread-bound function is not thread-safe, and may or may not be reentrant.
+ * \endinternal
+ *
+ * Neither reentrancy nor thread-safety, in this context, mean that a function
+ * may be called simultaneously from the same thread, for instance from a
+ * callback invoked by the function. This may deadlock and isn't allowed unless
+ * separately documented.
+ *
+ * \if internal
+ * A class is defined as reentrant, thread-safe or thread-bound if all its
+ * member functions are reentrant, thread-safe or thread-bound respectively.
+ * Some member functions may additionally be documented as having additional
+ * thread-related attributes.
+ *
+ * \else
+ *
+ * A class is defined as reentrant or thread-safe if all its member functions
+ * are reentrant or thread-safe respectively. Some member functions may
+ * additionally be documented as having additional thread-related attributes.
+ *
+ * \endif
+ *
+ * Most classes are reentrant but not thread-safe, as making them fully
+ * thread-safe would incur locking costs considered prohibitive for the
+ * expected use cases.
+ */
diff --git a/src/libcamera/base/thread.cpp b/src/libcamera/base/thread.cpp
index 72733431..8735670b 100644
--- a/src/libcamera/base/thread.cpp
+++ b/src/libcamera/base/thread.cpp
@@ -64,42 +64,6 @@
  * receiver's event loop, running in the receiver's thread. This mechanism can
  * be overridden by selecting a different connection type when calling
  * Signal::connect().
- *
- * \section thread-reentrancy Reentrancy and Thread-Safety
- *
- * Through the documentation, several terms are used to define how classes and
- * their member functions can be used from multiple threads.
- *
- * - A **reentrant** function may be called simultaneously from multiple
- *   threads if and only if each invocation uses a different instance of the
- *   class. This is the default for all member functions not explictly marked
- *   otherwise.
- *
- * - \anchor thread-safe A **thread-safe** function may be called
- *   simultaneously from multiple threads on the same instance of a class. A
- *   thread-safe function is thus reentrant. Thread-safe functions may also be
- *   called simultaneously with any other reentrant function of the same class
- *   on the same instance.
- *
- * - \anchor thread-bound A **thread-bound** function may be called only from
- *   the thread that the class instances lives in (see section \ref
- *   thread-objects). For instances of classes that do not derive from the
- *   Object class, this is the thread in which the instance was created. A
- *   thread-bound function is not thread-safe, and may or may not be reentrant.
- *
- * Neither reentrancy nor thread-safety, in this context, mean that a function
- * may be called simultaneously from the same thread, for instance from a
- * callback invoked by the function. This may deadlock and isn't allowed unless
- * separately documented.
- *
- * A class is defined as reentrant, thread-safe or thread-bound if all its
- * member functions are reentrant, thread-safe or thread-bound respectively.
- * Some member functions may additionally be documented as having additional
- * thread-related attributes.
- *
- * Most classes are reentrant but not thread-safe, as making them fully
- * thread-safe would incur locking costs considered prohibitive for the
- * expected use cases.
  */
 
 /**
-- 
2.34.1