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Re: [Qemu-devel] [PATCH 07/18] qom: add link properties

From: Avi Kivity
Subject: Re: [Qemu-devel] [PATCH 07/18] qom: add link properties
Date: Thu, 01 Dec 2011 17:00:49 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111115 Thunderbird/8.0

On 12/01/2011 04:53 PM, Anthony Liguori wrote:
>>  What does the client code looks like for link<PCIDevice>?
> I'm not sure what you mean by client code,


> but consider a device called UsbController that looks like:
> struct UsbController
> {
>     DeviceState parent;
>     UsbDevice *slave; // link property
> };
> To add this as a link, somewhere in the init function you would do:
> static void usb_controller_initfn(UsbController *dev)
> {
>    ...
>    qdev_property_add_link(DEVICE(dev), "slave", "UsbDevice",
>                           (DeviceState **)&dev->slave, NULL);
> }

- this is an object property, not a class property, so to get a list of
properties we need to instantiate an object.
- "UsbDevice" as the type is not type safe at compile time
- ditto for the cast

> If you want to set the property explicitly, you would just do:
>   dev->slave = some_other_device
> You don't need to use any special function to manipulate the link.
> Stylistically, I'd prefer that all devices exposed accessor functions
> and that you did these things through accessors so that we had clear
> rules about what's public and private.

Also, so we can have observers that trigger on changes.

error compiling committee.c: too many arguments to function

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