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

[Logan Gunthorpe <logang@deltatee.com>]

On 2021-03-12 7:32 p.m., Ira Weiny wrote:
> 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?

Yeah, there are subtle differences in prototype. But yes, they can
probably be combined. Will do for future postings.

>> + * 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?

Yes, that's correct.

Logan