linux-kernel - Re: [RFC PATCH v2 10/27] NTB: core: Add .get_pci_epc() to ntb_dev

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Message-ID: <aS3u7Ub+yY1oWD9i@lizhi-Precision-Tower-5810>
Date: Mon, 1 Dec 2025 14:39:25 -0500
From: Frank Li <Frank.li@....com>
To: Koichiro Den <den@...inux.co.jp>
Cc: ntb@...ts.linux.dev, linux-pci@...r.kernel.org,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	mani@...nel.org, kwilczynski@...nel.org, kishon@...nel.org,
	bhelgaas@...gle.com, corbet@....net, vkoul@...nel.org,
	jdmason@...zu.us, dave.jiang@...el.com, allenbh@...il.com,
	Basavaraj.Natikar@....com, Shyam-sundar.S-k@....com,
	kurt.schwemmer@...rosemi.com, logang@...tatee.com,
	jingoohan1@...il.com, lpieralisi@...nel.org, robh@...nel.org,
	jbrunet@...libre.com, fancer.lancer@...il.com, arnd@...db.de,
	pstanner@...hat.com, elfring@...rs.sourceforge.net
Subject: Re: [RFC PATCH v2 10/27] NTB: core: Add .get_pci_epc() to ntb_dev_ops

On Sun, Nov 30, 2025 at 01:03:48AM +0900, Koichiro Den wrote:
> Add an optional get_pci_epc() callback to retrieve the underlying
> pci_epc device associated with the NTB implementation.

EPC run at EP side, this is running at RC side. Why need get EP side's
controller pointer?

Frank
>
> Signed-off-by: Koichiro Den <den@...inux.co.jp>
> ---
>  drivers/ntb/hw/epf/ntb_hw_epf.c | 11 +----------
>  include/linux/ntb.h             | 21 +++++++++++++++++++++
>  2 files changed, 22 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/ntb/hw/epf/ntb_hw_epf.c b/drivers/ntb/hw/epf/ntb_hw_epf.c
> index a3ec411bfe49..d55ce6b0fad4 100644
> --- a/drivers/ntb/hw/epf/ntb_hw_epf.c
> +++ b/drivers/ntb/hw/epf/ntb_hw_epf.c
> @@ -9,6 +9,7 @@
>  #include <linux/delay.h>
>  #include <linux/module.h>
>  #include <linux/pci.h>
> +#include <linux/pci-epf.h>
>  #include <linux/slab.h>
>  #include <linux/ntb.h>
>
> @@ -49,16 +50,6 @@
>
>  #define NTB_EPF_COMMAND_TIMEOUT	1000 /* 1 Sec */
>
> -enum pci_barno {
> -	NO_BAR = -1,
> -	BAR_0,
> -	BAR_1,
> -	BAR_2,
> -	BAR_3,
> -	BAR_4,
> -	BAR_5,
> -};
> -
>  enum epf_ntb_bar {
>  	BAR_CONFIG,
>  	BAR_PEER_SPAD,
> diff --git a/include/linux/ntb.h b/include/linux/ntb.h
> index d7ce5d2e60d0..04dc9a4d6b85 100644
> --- a/include/linux/ntb.h
> +++ b/include/linux/ntb.h
> @@ -64,6 +64,7 @@ struct ntb_client;
>  struct ntb_dev;
>  struct ntb_msi;
>  struct pci_dev;
> +struct pci_epc;
>
>  /**
>   * enum ntb_topo - NTB connection topology
> @@ -256,6 +257,7 @@ static inline int ntb_ctx_ops_is_valid(const struct ntb_ctx_ops *ops)
>   * @msg_clear_mask:	See ntb_msg_clear_mask().
>   * @msg_read:		See ntb_msg_read().
>   * @peer_msg_write:	See ntb_peer_msg_write().
> + * @get_pci_epc:	See ntb_get_pci_epc().
>   */
>  struct ntb_dev_ops {
>  	int (*port_number)(struct ntb_dev *ntb);
> @@ -331,6 +333,7 @@ struct ntb_dev_ops {
>  	int (*msg_clear_mask)(struct ntb_dev *ntb, u64 mask_bits);
>  	u32 (*msg_read)(struct ntb_dev *ntb, int *pidx, int midx);
>  	int (*peer_msg_write)(struct ntb_dev *ntb, int pidx, int midx, u32 msg);
> +	struct pci_epc *(*get_pci_epc)(struct ntb_dev *ntb);
>  };
>
>  static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops)
> @@ -393,6 +396,9 @@ static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops)
>  		/* !ops->msg_clear_mask == !ops->msg_count	&& */
>  		!ops->msg_read == !ops->msg_count		&&
>  		!ops->peer_msg_write == !ops->msg_count		&&
> +
> +		/* Miscellaneous optional callbacks */
> +		/* ops->get_pci_epc			&& */
>  		1;
>  }
>
> @@ -1567,6 +1573,21 @@ static inline int ntb_peer_msg_write(struct ntb_dev *ntb, int pidx, int midx,
>  	return ntb->ops->peer_msg_write(ntb, pidx, midx, msg);
>  }
>
> +/**
> + * ntb_get_pci_epc() - get backing PCI endpoint controller if possible.
> + * @ntb:	NTB device context.
> + *
> + * Get the backing PCI endpoint controller representation.
> + *
> + * Return: A pointer to the pci_epc instance if available. or %NULL if not.
> + */
> +static inline struct pci_epc __maybe_unused *ntb_get_pci_epc(struct ntb_dev *ntb)
> +{
> +	if (!ntb->ops->get_pci_epc)
> +		return NULL;
> +	return ntb->ops->get_pci_epc(ntb);
> +}
> +
>  /**
>   * ntb_peer_resource_idx() - get a resource index for a given peer idx
>   * @ntb:	NTB device context.
> --
> 2.48.1
>