Generally speaking, the following steps should be taken in order to write a
new QMP command.
-1. Write the command's and type(s) specification in the QAPI schema file
- (qapi-schema.json in the root source directory)
+1. Define the command and any types it needs in the appropriate QAPI
+ schema module.
2. Write the QMP command itself, which is a regular C function. Preferably,
the command should be exported by some QEMU subsystem. But it can also be
Our command will be called "hello-world". It takes no arguments, nor does it
return any data.
-The first step is to add the following line to the bottom of the
-qapi-schema.json file:
+The first step is defining the command in the appropriate QAPI schema
+module. We pick module qapi/misc.json, and add the following line at
+the bottom:
{ 'command': 'hello-world' }
documentation.
There are many examples of such documentation in the schema file already, but
-here goes "hello-world"'s new entry for the qapi-schema.json file:
+here goes "hello-world"'s new entry for qapi/misc.json:
##
# @hello-world
allocated by the implementation. This is so because the QAPI also generates
a function to free its types and it cannot distinguish between dynamically
or statically allocated strings
-6. You have to include the "qmp-commands.h" header file in qemu-timer.c,
- otherwise qemu won't build
+6. You have to include "qapi/qmp-commands-misc.h" in qemu-timer.c
Time to test the new command. Build qemu, run it as described in the "Testing"
section and try this: