From 13d8e05adf9dd06c74fcc6ba42ec4bf780fd557f Mon Sep 17 00:00:00 2001 From: Dragos Tatulea Date: Wed, 27 Aug 2025 17:39:55 +0300 Subject: queue_api: add support for fetching per queue DMA dev For zerocopy (io_uring, devmem), there is an assumption that the parent device can do DMA. However that is not always the case: - Scalable Function netdevs [1] have the DMA device in the grandparent. - For Multi-PF netdevs [2] queues can be associated to different DMA devices. This patch introduces the a queue based interface for allowing drivers to expose a different DMA device for zerocopy. [1] Documentation/networking/device_drivers/ethernet/mellanox/mlx5/switchdev.rst [2] Documentation/networking/multi-pf-netdev.rst Signed-off-by: Dragos Tatulea Reviewed-by: Pavel Begunkov Reviewed-by: Mina Almasry Link: https://patch.msgid.link/20250827144017.1529208-3-dtatulea@nvidia.com Signed-off-by: Jakub Kicinski --- net/core/netdev_queues.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) create mode 100644 net/core/netdev_queues.c (limited to 'net/core/netdev_queues.c') diff --git a/net/core/netdev_queues.c b/net/core/netdev_queues.c new file mode 100644 index 000000000000..251f27a8307f --- /dev/null +++ b/net/core/netdev_queues.c @@ -0,0 +1,27 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +#include + +/** + * netdev_queue_get_dma_dev() - get dma device for zero-copy operations + * @dev: net_device + * @idx: queue index + * + * Get dma device for zero-copy operations to be used for this queue. + * When such device is not available or valid, the function will return NULL. + * + * Return: Device or NULL on error + */ +struct device *netdev_queue_get_dma_dev(struct net_device *dev, int idx) +{ + const struct netdev_queue_mgmt_ops *queue_ops = dev->queue_mgmt_ops; + struct device *dma_dev; + + if (queue_ops && queue_ops->ndo_queue_get_dma_dev) + dma_dev = queue_ops->ndo_queue_get_dma_dev(dev, idx); + else + dma_dev = dev->dev.parent; + + return dma_dev && dma_dev->dma_mask ? dma_dev : NULL; +} + -- cgit