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

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Message-ID: <536garhbuvs4cxwyiajoggdbjpoa4blpd2aoou2xbi6bcsqilm@7furekczlvq6>
Date: Thu, 22 Jan 2026 23:58:09 +0900
From: Koichiro Den <den@...inux.co.jp>
To: Frank Li <Frank.li@....com>
Cc: dave.jiang@...el.com, cassel@...nel.org, mani@...nel.org, 
	kwilczynski@...nel.org, kishon@...nel.org, bhelgaas@...gle.com, geert+renesas@...der.be, 
	robh@...nel.org, vkoul@...nel.org, jdmason@...zu.us, allenbh@...il.com, 
	jingoohan1@...il.com, 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, linux-kselftest@...r.kernel.org, 
	arnd@...db.de, gregkh@...uxfoundation.org, joro@...tes.org, will@...nel.org, 
	robin.murphy@....com, magnus.damm@...il.com, krzk+dt@...nel.org, conor+dt@...nel.org, 
	corbet@....net, skhan@...uxfoundation.org, andriy.shevchenko@...ux.intel.com, 
	jbrunet@...libre.com, utkarsh02t@...il.com
Subject: Re: [RFC PATCH v4 15/38] PCI: endpoint: pci-epf-vntb: Implement
 .get_dma_dev()

On Mon, Jan 19, 2026 at 03:30:16PM -0500, Frank Li wrote:
> 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.

Thanks for pointing this out. That makes sense, I'll update the text as you
suggested.

Koichiro

> 
> 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
> >