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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 <dtatulea@nvidia.com> Reviewed-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Mina Almasry <almasrymina@google.com> Link: https://patch.msgid.link/20250827144017.1529208-3-dtatulea@nvidia.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
28 lines
761 B
C
28 lines
761 B
C
// SPDX-License-Identifier: GPL-2.0-or-later
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#include <net/netdev_queues.h>
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/**
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* netdev_queue_get_dma_dev() - get dma device for zero-copy operations
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* @dev: net_device
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* @idx: queue index
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*
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* Get dma device for zero-copy operations to be used for this queue.
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* When such device is not available or valid, the function will return NULL.
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*
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* Return: Device or NULL on error
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*/
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struct device *netdev_queue_get_dma_dev(struct net_device *dev, int idx)
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{
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const struct netdev_queue_mgmt_ops *queue_ops = dev->queue_mgmt_ops;
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struct device *dma_dev;
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if (queue_ops && queue_ops->ndo_queue_get_dma_dev)
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dma_dev = queue_ops->ndo_queue_get_dma_dev(dev, idx);
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else
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dma_dev = dev->dev.parent;
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return dma_dev && dma_dev->dma_mask ? dma_dev : NULL;
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}
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