Re: [PATCH 3/3] vDPA/ifcvf: get_config_size should return dev specific config size

[Stefano Garzarella]

On Wed, Apr 14, 2021 at 05:18:32PM +0800, Zhu Lingshan wrote:
get_config_size() should return the size based on the decected
device type.
Signed-off-by: Zhu Lingshan <lingshan....@intel.com>
---
drivers/vdpa/ifcvf/ifcvf_main.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
index 9b6a38b798fa..b48b9789b69e 100644
--- a/drivers/vdpa/ifcvf/ifcvf_main.c
+++ b/drivers/vdpa/ifcvf/ifcvf_main.c
@@ -347,7 +347,16 @@ static u32 ifcvf_vdpa_get_vq_align(struct vdpa_device 
*vdpa_dev)

static size_t ifcvf_vdpa_get_config_size(struct vdpa_device *vdpa_dev)
{
-       return sizeof(struct virtio_net_config);
+       struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
+       size_t size;
+
+       if (vf->dev_type == VIRTIO_ID_NET)
+               size = sizeof(struct virtio_net_config);
+
+       if (vf->dev_type == VIRTIO_ID_BLOCK)
+               size = sizeof(struct virtio_blk_config);
+
+       return size;

I'm not familiar with the ifcvf details, but can it happen that the 
device is not block or net?

Should we set `size` to 0 by default to handle this case or are we sure 
it's one of the two?

Maybe we should add a comment or a warning message in this case, to 
prevent some analysis tool or compiler from worrying that `size` might 
be uninitialized.

I was thinking something like this:

        switch(vf->dev_type) {
        case VIRTIO_ID_NET:
                size = sizeof(struct virtio_net_config);
                break;
        case VIRTIO_ID_BLOCK:
                size = sizeof(struct virtio_blk_config);
                break;
        default:
                /* or WARN(1, "") if dev_warn() not apply */
                dev_warn(... , "virtio ID [0x%x] not supported\n")
                size = 0;

        }

Thanks,
Stefano