linux-kernel - Re: [PATCH v9 02/24] dma-mapping: move the PCI P2PDMA mapping helpers to pci-p2pdma.h

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Message-ID: <aAwqBvLP3kaZsEdZ@bombadil.infradead.org>
Date: Fri, 25 Apr 2025 17:34:14 -0700
From: Luis Chamberlain <mcgrof@...nel.org>
To: Leon Romanovsky <leon@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
	Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
	Keith Busch <kbusch@...nel.org>, Jake Edge <jake@....net>,
	Jonathan Corbet <corbet@....net>, Jason Gunthorpe <jgg@...pe.ca>,
	Zhu Yanjun <zyjzyj2000@...il.com>,
	Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Sagi Grimberg <sagi@...mberg.me>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Logan Gunthorpe <logang@...tatee.com>,
	Yishai Hadas <yishaih@...dia.com>,
	Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
	Kevin Tian <kevin.tian@...el.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Jérôme Glisse <jglisse@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org, linux-rdma@...r.kernel.org,
	iommu@...ts.linux.dev, linux-nvme@...ts.infradead.org,
	linux-pci@...r.kernel.org, kvm@...r.kernel.org, linux-mm@...ck.org,
	Niklas Schnelle <schnelle@...ux.ibm.com>,
	Chuck Lever <chuck.lever@...cle.com>,
	Matthew Wilcox <willy@...radead.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Kanchan Joshi <joshi.k@...sung.com>,
	Chaitanya Kulkarni <kch@...dia.com>,
	Leon Romanovsky <leonro@...dia.com>
Subject: Re: [PATCH v9 02/24] dma-mapping: move the PCI P2PDMA mapping
 helpers to pci-p2pdma.h

On Wed, Apr 23, 2025 at 11:12:53AM +0300, Leon Romanovsky wrote:
> From: Christoph Hellwig <hch@....de>
> +enum pci_p2pdma_map_type {
> +	/*
> +	 * PCI_P2PDMA_MAP_UNKNOWN: Used internally for indicating the mapping
> +	 * type hasn't been calculated yet. Functions that return this enum
> +	 * never return this value.
> +	 */

This last sentence is confusing. How about:

* PCI_P2PDMA_MAP_UNKNOWN: Used internally as an initial state before
* the mapping type has been calculated. Exported routines for the API
* will never return this value.

> +	PCI_P2PDMA_MAP_UNKNOWN = 0,
> +
> +	/*
> +	 * Not a PCI P2PDMA transfer.
> +	 */
> +	PCI_P2PDMA_MAP_NONE,
> +
> +	/*
> +	 * PCI_P2PDMA_MAP_NOT_SUPPORTED: Indicates the transaction will
> +	 * traverse the host bridge and the host bridge is not in the
> +	 * allowlist. DMA Mapping routines should return an error when
> +	 * this is returned.
> +	 */
> +	PCI_P2PDMA_MAP_NOT_SUPPORTED,
> +
> +	/*
> +	 * PCI_P2PDMA_BUS_ADDR: Indicates that two devices can talk to

You mean   PCI_P2PDMA_MAP_BUS_ADDR

> + * pci_p2pdma_bus_addr_map - map a PCI_P2PDMA_MAP_BUS_ADDR P2P transfer

Hrm, maybe with a bit more clarity:

Translate a physical address to a bus address for a  PCI_P2PDMA_MAP_BUS_ADDR
transfer.


Other than that.

Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>

  Luis