Re: [RFC PATCH v2 04/11] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()

Ira Weiny
2021-03-13T02:32:27Z

On Thu, Mar 11, 2021 at 04:31:34PM -0700, Logan Gunthorpe wrote:
> Introduce pci_p2pdma_should_map_bus() which is meant to be called by
^^^^^^^^^^^^^^^^^^^^^^^^^
pci_p2pdma_dma_map_type() ???

FWIW I find this name confusing with pci_p2pdma_map_type() and looking at the
implementation I'm not clear why pci_p2pdma_dma_map_type() needs to exist?

Ira

[snip]

> +
> +/**
> + * pci_p2pdma_dma_map_type - determine if a DMA mapping should use the
> + * bus address, be mapped normally or fail
> + * @dev: device doing the DMA request
> + * @pgmap: dev_pagemap structure for the mapping
> + *
> + * Returns:
> + * 1 - if the page should be mapped with a bus address,
> + * 0 - if the page should be mapped normally through an IOMMU mapping or
> + * physical address; or
> + * -1 - if the device should not map the pages and an error should be
> + * returned
> + */
> +int pci_p2pdma_dma_map_type(struct device *dev, struct dev_pagemap *pgmap)
> +{
> + struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(pgmap);
> + struct pci_dev *client;
> +
> + if (!dev_is_pci(dev))
> + return -1;
> +
> + client = to_pci_dev(dev);
> +
> + switch (pci_p2pdma_map_type(p2p_pgmap->provider, client)) {
> + case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
> + return 0;
> + case PCI_P2PDMA_MAP_BUS_ADDR:
> + return 1;
> + default:
> + return -1;
> + }
> +}
> +EXPORT_SYMBOL_GPL(pci_p2pdma_dma_map_type);

I guess the main point here is to export this to the DMA layer?

Ira