Re: [net-next v1 08/16] memory-provider: dmabuf devmem memory provider

[Yinjun Zhang]

On Thu,  7 Dec 2023 16:52:39 -0800, Mina Almasry wrote:
<...>
> +static int mp_dmabuf_devmem_init(struct page_pool *pool)
> +{
> +	struct netdev_dmabuf_binding *binding = pool->mp_priv;
> +
> +	if (!binding)
> +		return -EINVAL;
> +
> +	if (!(pool->p.flags & PP_FLAG_DMA_MAP))
> +		return -EOPNOTSUPP;
> +
> +	if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
> +		return -EOPNOTSUPP;
> +
> +	netdev_dmabuf_binding_get(binding);
> +	return 0;
> +}
> +
> +static struct page *mp_dmabuf_devmem_alloc_pages(struct page_pool *pool,
> +						 gfp_t gfp)
> +{
> +	struct netdev_dmabuf_binding *binding = pool->mp_priv;
> +	struct page_pool_iov *ppiov;
> +
> +	ppiov = netdev_alloc_dmabuf(binding);

Since it only supports one-page allocation, we'd better add a check in
`ops->init()` that `pool->p.order` must be 0.

> +	if (!ppiov)
> +		return NULL;
> +
> +	ppiov->pp = pool;
> +	pool->pages_state_hold_cnt++;
> +	trace_page_pool_state_hold(pool, (struct page *)ppiov,
> +				   pool->pages_state_hold_cnt);
> +	return (struct page *)((unsigned long)ppiov | PP_IOV);
> +}
<...>