linux-kernel - Re: [RFC PATCH v4 18/38] NTB: ntb_transport: Use ntb_get_dma

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Message-ID: <aW6WW6S3Qq/usQyi@lizhi-Precision-Tower-5810>
Date: Mon, 19 Jan 2026 15:38:51 -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,
	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 18/38] NTB: ntb_transport: Use ntb_get_dma_dev()

On Sun, Jan 18, 2026 at 10:54:20PM +0900, Koichiro Den wrote:
> Replace direct use of ntb->pdev with ntb_get_dma_dev() for DMA-safe
> allocations and frees. This allows ntb_transport to operate on NTB
> implementations that are not backed by a PCI device from IOMMU
> perspective.
>
> Signed-off-by: Koichiro Den <den@...inux.co.jp>
> ---
Reviewed-by: Frank Li <Frank.Li@....com>
>  drivers/ntb/ntb_transport.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
> index 6ed680d0470f..7b320249629c 100644
> --- a/drivers/ntb/ntb_transport.c
> +++ b/drivers/ntb/ntb_transport.c
> @@ -771,13 +771,13 @@ static void ntb_transport_msi_desc_changed(void *data)
>  static void ntb_free_mw(struct ntb_transport_ctx *nt, int num_mw)
>  {
>  	struct ntb_transport_mw *mw = &nt->mw_vec[num_mw];
> -	struct pci_dev *pdev = nt->ndev->pdev;
> +	struct device *dev = ntb_get_dma_dev(nt->ndev);
>
> -	if (!mw->virt_addr)
> +	if (!dev || !mw->virt_addr)
>  		return;
>
>  	ntb_mw_clear_trans(nt->ndev, PIDX, num_mw);
> -	dma_free_coherent(&pdev->dev, mw->alloc_size,
> +	dma_free_coherent(dev, mw->alloc_size,
>  			  mw->alloc_addr, mw->dma_addr);
>  	mw->xlat_size = 0;
>  	mw->buff_size = 0;
> @@ -847,13 +847,13 @@ static int ntb_set_mw(struct ntb_transport_ctx *nt, int num_mw,
>  		      resource_size_t size)
>  {
>  	struct ntb_transport_mw *mw = &nt->mw_vec[num_mw];
> -	struct pci_dev *pdev = nt->ndev->pdev;
> +	struct device *dev = ntb_get_dma_dev(nt->ndev);
>  	size_t xlat_size, buff_size;
>  	resource_size_t xlat_align;
>  	resource_size_t xlat_align_size;
>  	int rc;
>
> -	if (!size)
> +	if (!dev || !size)
>  		return -EINVAL;
>
>  	rc = ntb_mw_get_align(nt->ndev, PIDX, num_mw, &xlat_align,
> @@ -876,12 +876,12 @@ static int ntb_set_mw(struct ntb_transport_ctx *nt, int num_mw,
>  	mw->buff_size = buff_size;
>  	mw->alloc_size = buff_size;
>
> -	rc = ntb_alloc_mw_buffer(mw, &pdev->dev, xlat_align);
> +	rc = ntb_alloc_mw_buffer(mw, dev, xlat_align);
>  	if (rc) {
>  		mw->alloc_size *= 2;
> -		rc = ntb_alloc_mw_buffer(mw, &pdev->dev, xlat_align);
> +		rc = ntb_alloc_mw_buffer(mw, dev, xlat_align);
>  		if (rc) {
> -			dev_err(&pdev->dev,
> +			dev_err(dev,
>  				"Unable to alloc aligned MW buff\n");
>  			mw->xlat_size = 0;
>  			mw->buff_size = 0;
> @@ -894,7 +894,7 @@ static int ntb_set_mw(struct ntb_transport_ctx *nt, int num_mw,
>  	rc = ntb_mw_set_trans(nt->ndev, PIDX, num_mw, mw->dma_addr,
>  			      mw->xlat_size);
>  	if (rc) {
> -		dev_err(&pdev->dev, "Unable to set mw%d translation", num_mw);
> +		dev_err(dev, "Unable to set mw%d translation", num_mw);
>  		ntb_free_mw(nt, num_mw);
>  		return -EIO;
>  	}
> --
> 2.51.0
>