linux-kernel - Re: [RFC PATCH v4 15/38] PCI: endpoint: pci-epf-vntb: Implement .get_dma

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Message-ID: <aW6UWJ6HLltjwhT/@lizhi-Precision-Tower-5810>
Date: Mon, 19 Jan 2026 15:30:16 -0500
From: Frank Li <Frank.li@....com>
To: Koichiro Den <den@...inux.co.jp>
Cc: dave.jiang@...el.com, cassel@...nel.org, mani@...nel.org,
	kwilczynski@...nel.org, kishon@...nel.org, bhelgaas@...gle.com,
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	lpieralisi@...nel.org, linux-pci@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org, devicetree@...r.kernel.org,
	dmaengine@...r.kernel.org, iommu@...ts.linux.dev,
	ntb@...ts.linux.dev, netdev@...r.kernel.org,
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	utkarsh02t@...il.com
Subject: Re: [RFC PATCH v4 15/38] PCI: endpoint: pci-epf-vntb: Implement
 .get_dma_dev()

On Sun, Jan 18, 2026 at 10:54:17PM +0900, Koichiro Den wrote:
> For DMA API allocations and mappings, pci-epf-vntb should provide an
> appropriate struct device for the NTB core/clients.
>
> Implement .get_dma_dev() and return the EPC parent device.

Simple said:

Implement .get_dma_dev() and return the EPC parent device for NTB
core/client's DMA allocations and mappings API.

Reviewed-by: Frank Li <Frank.Li@....com>
>
> Signed-off-by: Koichiro Den <den@...inux.co.jp>
> ---
>  drivers/pci/endpoint/functions/pci-epf-vntb.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> index 9fbc27000f77..7cd976757d15 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> @@ -1747,6 +1747,15 @@ static int vntb_epf_link_disable(struct ntb_dev *ntb)
>  	return 0;
>  }
>
> +static struct device *vntb_epf_get_dma_dev(struct ntb_dev *ndev)
> +{
> +	struct epf_ntb *ntb = ntb_ndev(ndev);
> +
> +	if (!ntb || !ntb->epf)
> +		return NULL;
> +	return ntb->epf->epc->dev.parent;
> +}
> +
>  static void *vntb_epf_get_private_data(struct ntb_dev *ndev)
>  {
>  	struct epf_ntb *ntb = ntb_ndev(ndev);
> @@ -1780,6 +1789,7 @@ static const struct ntb_dev_ops vntb_epf_ops = {
>  	.db_clear_mask		= vntb_epf_db_clear_mask,
>  	.db_clear		= vntb_epf_db_clear,
>  	.link_disable		= vntb_epf_link_disable,
> +	.get_dma_dev		= vntb_epf_get_dma_dev,
>  	.get_private_data	= vntb_epf_get_private_data,
>  };
>
> --
> 2.51.0
>