Re: [Qemu-devel] [PATCH v2] Man page: Add -global description

[Anthony Liguori <anthony@codemonkey.ws>]

On 03/14/2012 01:21 PM, Peter Maydell wrote:
> On 14 March 2012 08:53, Miroslav Rezanina<mrezanin@redhat.com>  wrote:
>> --- a/qemu-options.hx
>> +++ b/qemu-options.hx
>> @@ -292,9 +292,13 @@ DEF("global", HAS_ARG, QEMU_OPTION_global,
>>      "                set a global default for a driver property\n",
>>      QEMU_ARCH_ALL)
>>   STEXI
>> -@item -global
>> +@item -global @var{driver}.@var{property}=@var{value}
>
> We seem to use @var{prop}, not @var{property}, elsewhere in the docs.
>
>>   @findex -global
>> -TODO
>> +Set default value of @var{driver}'s @var{property} to @var{value}, e.g.:
>> +
>> +@example
>> +qemu -global ide-drive.physical_block_size=4096 -drive file=file,if=ide,index=0
>> +@end example
>>   ETEXI
>
> This is missing any motivation for why you would want to actually
> use this option. How about:
>
> "In particular, you can use this to set driver properties for devices which
> are created automatically by the machine model. (To create a device which is
> not created automatically and set properties on it, use -device.)"
>
> ?
>
> That's still not great, but I think it helps a little.
>
> (ideally if -device/-global are the new standard interface we should have a
> section explaining the general concepts and syntax and then documentation of
> how to do specific things like networking via -device, and relegate all the
> 'legacy' options to a section clearly marked as 'legacy' with pointers back
> to the new ways of doing the same thing. That would be a much bigger job,
> though.)

Just while we're here, I'll be posting the following shortly:

commit 82aff428155d469ab705294486cc26cb34947999
Author: Anthony Liguori <aliguori@us.ibm.com>
Date:   Fri Dec 23 11:30:45 2011 -0600

qdev: don't allow globals to be set by bus name

This is technically a compatibility breaker.  However:

1) libvirt does not rely on this (it always uses the driver name)

2) This behavior isn't actually documented anywhere (the docs just say driver).

3) I suspect there are less than three people on earth that even know this is
    possible (minus the people reading this message).

So I think we can safely break it :-)

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Regards,

Anthony Liguori

>
> -- PMM
>