Document the plugin API in Documentation/manual.txt and provide an
example plugin.
Signed-off-by: Andrei Ziureaev <andrei.ziureaev@xxxxxxx>
---
Documentation/manual.txt | 74 ++++++++++++++++++++++++++++++++
plugins/example/Makefile.example | 19 ++++++++
plugins/example/example.c | 29 +++++++++++++
3 files changed, 122 insertions(+)
create mode 100644 plugins/example/Makefile.example
create mode 100644 plugins/example/example.c
diff --git a/Documentation/manual.txt b/Documentation/manual.txt
index adf5ccb..18624aa 100644
--- a/Documentation/manual.txt
+++ b/Documentation/manual.txt
@@ -10,6 +10,10 @@ I - "dtc", the device tree compiler
4.1) Overview
4.2) Properties
4.3) Labels and References
+ 5) Plugins
+ 5.1) Loading plugins
+ 5.2) Exporting Functionality
+ 5.3) Building Plugins
II - The DT block format
1) Header
@@ -115,6 +119,16 @@ Options:
-d <dependency_filename>
Generate a dependency file during compilation.
+ -l, --plugin <plugin name>[,key][,value]
+ Load a plugin and, optionally, pass it an argument.
+ plugin name - the name of the shared object without the extension (can contain a path)
+ key - the name of the argument
+ value - can be omitted
+ Example: dtc -lsome-plugin,o,out.dts -lsome-plugin,help -l path/to/another-plugin [...]
+
+ -L, --plugin-dir <arg>
+ The directory in which to search for plugins
+
-q
Quiet: -q suppress warnings, -qq errors, -qqq all
@@ -272,6 +286,66 @@ And used in properties, labels may appear before or after any value:
};
+5) Plugins
+
+Plugins are shared libraries that DTC loads at runtime using
+
+ dlopen(path, RTLD_NOW | RTLD_GLOBAL | RTLD_DEEPBIND)
+
+RTLD_NOW means they are loaded immediately (right before the parsing
+stage).
+
+RTLD_GLOBAL means their symbols can be used by other plugins.
+
+RTLD_DEEPBIND means the dynamic linker will look for symbols within the
+plugin first, before searching in the main program and other plugins.
+
+All plugins must include the "dtc-plugin.h" header.
+
+
+5.1) Loading plugins
+
+Please, refer to the -l and -L options in the "Command Line" section.
+
+
+5.2) Exporting Functionality
+
+Plugins export functionality through the "EXPORT_FUNCTION(type, fn)"
+macro, where "type" is one of the typedefs from "dtc-plugin.h", and
+"fn" is the function that will be called by DTC. Each type of function
+gets called once for each plugin.
+
+Every plugin must export a function of type "init_fn_t".
+
+"plugins/example/example.c" shows how an init function can be used.
+
+
+5.3) Building Plugins
+
+The command "make plugins" infers the names of the shared library files
+from the names of directories under "plugins/". For example, the
+presence of a
+
+ plugins/example/
+
+directory means that make will try to build
+
+ plugins/example/example.so
+
+from
+
+ plugins/example/example.c
+
+It will then make a symlink
+
+ plugins/example.so
+
+for convenience.
+
+Please, see "plugins/example/Makefile.example" for how to override the
+defaut behavior.
+
+
II - The DT block format
========================
diff --git a/plugins/example/Makefile.example b/plugins/example/Makefile.example
new file mode 100644
index 0000000..56d4e17
--- /dev/null
+++ b/plugins/example/Makefile.example
@@ -0,0 +1,19 @@
+# Optional per-plugin makefile
+#
+# Here you can add gcc flags:
+# PLUGIN_CFLAGS_example = -some-flag
+#
+# Add libraries:
+# PLUGIN_LDLIBS_example = -lsome-lib
+#
+# Add files to clean:
+# PLUGIN_CLEANFILES += $(PLUGIN_dir)/example/*.tmp
+#
+# Or override the default rules:
+# $(PLUGIN_dir)/example/example.$(SHAREDLIB_EXT): $(PLUGIN_dir)/example/example.o
+# @$(VECHO) LD $@
+# ...
+#
+# $(PLUGIN_dir)/example/example.o: $(PLUGIN_dir)/example/example.c
+# @$(VECHO) CC $@
+# ...
diff --git a/plugins/example/example.c b/plugins/example/example.c
new file mode 100644
index 0000000..3bbf9ea
--- /dev/null
+++ b/plugins/example/example.c
@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <string.h>
+
+#include "dtc-plugin.h"
+
+#define NAME "example: "
+
+static int init_example(struct plugin_version v, int argc, struct plugin_arg *argv)
+{
+ if (!dtc_plugin_default_version_check(v)) {
+ fprintf(stderr, NAME"Plugin is incompatible with this version of DTC\n");
+ return 1;
+ }
+
+ for (int i = 0; i < argc; i++) {
+ if (strcmp(argv[i].key, "h") == 0
+ || strcmp(argv[i].key, "help") == 0) {
+ printf(NAME"This is an example plugin. It prints its arguments.\n");
+ return 1;
+ } else {
+ printf(NAME"%s: %s\n", argv[i].key,
+ argv[i].value ? argv[i].value : "");
+ }
+ }
+
+ printf(NAME"Loaded plugin 'example'\n");
+ return 0;
+}
+EXPORT_FUNCTION(init_fn_t, init_example);
--
2.17.1
