Re: [PATCH 4/5] misc: vop: set VIRTIO_F_ACCESS_PLATFORM for nocoherent platform

[Greg KH]

On Fri, Sep 25, 2020 at 03:26:29PM +0800, Sherry Sun wrote:
> Set VIRTIO_F_ACCESS_PLATFORM feature for nocoherent platform, since
> it needs the DMA API for virtio.
> 
> Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
> Signed-off-by: Joakim Zhang <qiangqing.zhang@xxxxxxx>
> ---
>  drivers/misc/mic/vop/vop_main.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/misc/mic/vop/vop_main.c b/drivers/misc/mic/vop/vop_main.c
> index d3645122c983..d609f0dc6124 100644
> --- a/drivers/misc/mic/vop/vop_main.c
> +++ b/drivers/misc/mic/vop/vop_main.c
> @@ -125,6 +125,9 @@ static void vop_transport_features(struct virtio_device *vdev)
>  	 * creates virtio rings on preallocated memory.
>  	 */
>  	__virtio_clear_bit(vdev, VIRTIO_F_RING_PACKED);
> +
> +	if (!dev_is_dma_coherent(vdev->dev.parent))
> +		__virtio_set_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);

Why look at the parent and not the device itself?