[Qemu-devel] Re: [PATCHv4 1/2] qdev: add bit property type

[Gerd Hoffmann]

On 12/24/09 13:43, Michael S. Tsirkin wrote:
> This adds "bit" property type, which is a boolean stored in a 32 bit
> integer field, with legal values on and off.  Will be used by virtio for
> feature bits.

> +static void *qdev_bit_prop_ptr(DeviceState *dev, Property *prop)
> +{
> +    void *ptr = dev;
> +    assert(prop->info->type == PROP_TYPE_BIT);
> +    ptr += prop->offset / 32;
> +    return ptr;
> +}

I don't like that idea.  IMHO prop->offset should be specified in bytes 
no matter what the property is.  Better add a new prop->bitnr field to 
specify which bit of the 32bit word should be toggled.  Then you don't 
need this function in the first place.

cheers,
  Gerd