[Qemu-devel] Re: [PATCH 06/41] virtio: Use DO_UPCAST instead of a cast

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Dec 02, 2009 at 01:04:04PM +0100, Juan Quintela wrote:
> virtio_common_init() creates a struct with the right size, DO_UPCAST
> is the appropiate thing here
> 
> Signed-off-by: Juan Quintela <quintela@redhat.com>

BTW why not container_of? That one does not require
field to be at the beginning of structure.

> ---
>  hw/virtio-balloon.c |    4 ++--
>  hw/virtio-blk.c     |    8 ++++----
>  hw/virtio-console.c |    3 ++-
>  hw/virtio-net.c     |    8 ++++----
>  4 files changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
> index 2310ab0..6f60fb1 100644
> --- a/hw/virtio-balloon.c
> +++ b/hw/virtio-balloon.c
> @@ -167,11 +167,11 @@ static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
>  VirtIODevice *virtio_balloon_init(DeviceState *dev)
>  {
>      VirtIOBalloon *s;
> -
> -    s = (VirtIOBalloon *)virtio_common_init("virtio-balloon",
> +    VirtIODevice *vdev = virtio_common_init("virtio-balloon",
>                                              VIRTIO_ID_BALLOON,
>                                              8, sizeof(VirtIOBalloon));
> 
> +    s = DO_UPCAST(VirtIOBalloon, vdev, vdev);
>      s->vdev.get_config = virtio_balloon_get_config;
>      s->vdev.set_config = virtio_balloon_set_config;
>      s->vdev.get_features = virtio_balloon_get_features;
> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
> index 39ebc37..918be74 100644
> --- a/hw/virtio-blk.c
> +++ b/hw/virtio-blk.c
> @@ -487,11 +487,11 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, DriveInfo *dinfo)
>      char *ps = (char *)drive_get_serial(dinfo->bdrv);
>      size_t size = strlen(ps) ? sizeof(struct virtio_blk_config) :
>  	    offsetof(struct virtio_blk_config, _blk_size);
> +    VirtIODevice *vdev = virtio_common_init("virtio-blk", VIRTIO_ID_BLOCK,
> +                                            size,
> +                                            sizeof(VirtIOBlock));
> 
> -    s = (VirtIOBlock *)virtio_common_init("virtio-blk", VIRTIO_ID_BLOCK,
> -                                          size,
> -                                          sizeof(VirtIOBlock));
> -
> +    s = DO_UPCAST(VirtIOBlock, vdev, vdev);
>      s->config_size = size;
>      s->vdev.get_config = virtio_blk_update_config;
>      s->vdev.get_features = virtio_blk_get_features;
> diff --git a/hw/virtio-console.c b/hw/virtio-console.c
> index 9f1a602..57f5e9d 100644
> --- a/hw/virtio-console.c
> +++ b/hw/virtio-console.c
> @@ -121,9 +121,10 @@ static int virtio_console_load(QEMUFile *f, void *opaque, int version_id)
>  VirtIODevice *virtio_console_init(DeviceState *dev)
>  {
>      VirtIOConsole *s;
> -    s = (VirtIOConsole *)virtio_common_init("virtio-console",
> +    VirtIODevice *vdev = virtio_common_init("virtio-console",
>                                              VIRTIO_ID_CONSOLE,
>                                              0, sizeof(VirtIOConsole));
> +    s = DO_UPCAST(VirtIOConsole, vdev, vdev);
>      s->vdev.get_features = virtio_console_get_features;
> 
>      s->ivq = virtio_add_queue(&s->vdev, 128, virtio_console_handle_input);
> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> index f518d78..1b8ce14 100644
> --- a/hw/virtio-net.c
> +++ b/hw/virtio-net.c
> @@ -817,11 +817,11 @@ VirtIODevice *virtio_net_init(DeviceState *dev, NICConf *conf)
>  {
>      VirtIONet *n;
>      static int virtio_net_id;
> +    VirtIODevice *vdev = virtio_common_init("virtio-net", VIRTIO_ID_NET,
> +                                            sizeof(struct virtio_net_config),
> +                                            sizeof(VirtIONet));
> 
> -    n = (VirtIONet *)virtio_common_init("virtio-net", VIRTIO_ID_NET,
> -                                        sizeof(struct virtio_net_config),
> -                                        sizeof(VirtIONet));
> -
> +    n = DO_UPCAST(VirtIONet, vdev, vdev);
>      n->vdev.get_config = virtio_net_get_config;
>      n->vdev.set_config = virtio_net_set_config;
>      n->vdev.get_features = virtio_net_get_features;
> -- 
> 1.6.5.2