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Date: Mon, 14 Dec 2009 21:20:46 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property
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To: Gerd Hoffmann <kraxel@redhat.com>
Cc: qemu-devel@nongnu.org

On Mon, Dec 14, 2009 at 12:37:29PM +0100, Gerd Hoffmann wrote:
> On 12/14/09 12:10, Michael S. Tsirkin wrote:
>> On Mon, Dec 14, 2009 at 11:24:41AM +0100, Gerd Hoffmann wrote:
>> for block:
>>      if (strcmp(s->serial_str, "0"))
>>          features |= 1<<  VIRTIO_BLK_F_IDENTIFY;
>>
>>      if (bdrv_is_read_only(s->bs))
>>          features |= 1<<  VIRTIO_BLK_F_RO;
>
> Sure you want these be configurable?
>
>> Also, I'd like these things to be saved in bits and not add a ton
>> of fields in device. Ideas how to do this?
>
> I guess you only want disable features?
>
> You could have a bitmap property then, which accepts names for the bits.  
>  It would need a table like this ...
>
>    char *bitnames[] = {
> 	[ VIRTIO_BLK_F_IDENTIFY ] = "blk-identify",
> 	[ VIRTIO_BLK_F_RO       [ = "blk-ro",
> 	[ ... ]
>    };
>
> Then the property parser would accepts strings such as 'bit1|bit2' and  
> you can have
>
>   -device 'virtio-blk-pci,disable=blk-identify|ring-indirect'
>
> The driver will just do 'vdev->host_features &= ~disable'.
>
> cheers,
>   Gerd

Is there an example of an existing property that is like this?

-- 
MST