docs/devel: mention the spacing requirement for QOM

We have a more complete document on QOM but we should at least mention
the style requirements in the style guide.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-Id: <20230424092249.58552-18-alex.bennee@linaro.org>
This commit is contained in:
Alex Bennée 2023-04-24 10:22:48 +01:00
parent 6a0057aa22
commit 067109a11c
2 changed files with 39 additions and 0 deletions

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@ -1,3 +1,5 @@
.. _qom:
===========================
The QEMU Object Model (QOM)
===========================

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@ -628,6 +628,43 @@ are still some caveats to beware of
QEMU Specific Idioms
********************
QEMU Object Model Declarations
==============================
The QEMU Object Model (QOM) provides a framework for handling objects
in the base C language. The first declaration of a storage or class
structure should always be the parent and leave a visual space between
that declaration and the new code. It is also useful to separate
backing for properties (options driven by the user) and internal state
to make navigation easier.
For a storage structure the first declaration should always be called
"parent_obj" and for a class structure the first member should always
be called "parent_class" as below:
.. code-block:: c
struct MyDeviceState {
DeviceState parent_obj;
/* Properties */
int prop_a;
char *prop_b;
/* Other stuff */
int internal_state;
};
struct MyDeviceClass {
DeviceClass parent_class;
void (*new_fn1)(void);
bool (*new_fn2)(CPUState *);
};
Note that there is no need to provide typedefs for QOM structures
since these are generated automatically by the QOM declaration macros.
See :ref:`qom` for more details.
Error handling and reporting
============================