Re: [Qemu-devel] [RFC] Introduce module API to QEMU

[Anthony Liguori]

Paul Brook wrote:
> > This patch introduces a module API similar to what's in the Linux kernel. 
> > This includes module_init/module_exit functions that register functions
> > that are run at init and exit respectively.
> >     
>
> Wouldn't it be much simpler to just have a list of device names, and assume 
> the each device is implemented in $devicename., and provides 
> $devicename_register ?
>
> It's then an extremely simple shell script to collate and call these.
>   

It doesn't generalize very well.  For instance, the VNC server is not a 
device but it needs to be able to register as a DisplayState backend.

The other way to do this typically is to have module_init() functions 
that turn a function into a non-static function with some sort of 
annotation that disappears at compile time.  For instance:

module_init(virtnet_init);

Would become:

int qemu__module__init__virtnet_init(void)
{
    return virtnet_init();
}

with #define qemu__init__function

You then have something that searches for these functions.  The problem 
with this approach is that virtnet_init must be a unique name because 
it's a non-static.  You can add some uniqueness by playing with __LINE__ 
but that doesn't make any guarantees.

This is doable but IMHO a worse solution.  I'd rather use 
__attribute__((constructor)) for now and introduce the above only if we 
ever support something other than GCC.

Regards,

Anthony Liguori
> Paul
>
>
>