Re: [PATCH v2 4/9] PCI: endpoint: Introduce pci_epc_bar_type BAR_DISABLED

[Frank Li <Frank.li@nxp.com>]

On Wed, Feb 25, 2026 at 06:03:27PM +0100, Niklas Cassel wrote:
> Add a pci_epc_bar_type BAR_DISABLED to more clearly differentiate from
> BAR_RESERVED.
>
> This BAR type will only be used to describe a BAR that the EPC driver
> should disable, and will thus never be available to an EPF drive.
> (Unlike BAR_RESERVED, which will never be disabled by default by an EPC
> driver.)
>
> Tested-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
> Reviewed-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
> Co-developed-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
> Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
> Signed-off-by: Niklas Cassel <cassel@kernel.org>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>
>  drivers/pci/endpoint/pci-epc-core.c |  5 +++--
>  include/linux/pci-epc.h             | 12 ++++++++++--
>  2 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index 1ad2f62963c8..32cf9a9bc365 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -103,9 +103,10 @@ enum pci_barno pci_epc_get_next_free_bar(const struct pci_epc_features
>  		bar++;
>
>  	for (i = bar; i < PCI_STD_NUM_BARS; i++) {
> -		/* If the BAR is not reserved, return it. */
> +		/* If the BAR is not reserved or disabled, return it. */
>  		if (epc_features->bar[i].type != BAR_RESERVED &&
> -		    epc_features->bar[i].type != BAR_64BIT_UPPER)
> +		    epc_features->bar[i].type != BAR_64BIT_UPPER &&
> +		    epc_features->bar[i].type != BAR_DISABLED)
>  			return i;
>  	}
>
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index f7f48f43d370..63a24ebf144c 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -191,7 +191,14 @@ struct pci_epc {
>   * @BAR_RESIZABLE: The BAR implements the PCI-SIG Resizable BAR Capability.
>   *		   NOTE: An EPC driver can currently only set a single supported
>   *		   size.
> - * @BAR_RESERVED: The BAR should not be touched by an EPF driver.
> + * @BAR_RESERVED: Used for HW-backed BARs (e.g. MSI-X table, DMA regs). The BAR
> + *		  should not be disabled by an EPC driver. The BAR should not be
> + *		  reprogrammed by an EPF driver. An EPF driver is allowed to
> + *		  disable the BAR if absolutely necessary. (However, right now
> + *		  there is no EPC operation to disable a BAR that has not been
> + *		  programmed using pci_epc_set_bar().)
> + * @BAR_DISABLED: The BAR should be disabled by an EPC driver. The BAR will be
> + *		  unavailable to an EPF driver.
>   * @BAR_64BIT_UPPER: Should only be set on a BAR if the preceding BAR is marked
>   *		     as only_64bit.
>   */
> @@ -200,6 +207,7 @@ enum pci_epc_bar_type {
>  	BAR_FIXED,
>  	BAR_RESIZABLE,
>  	BAR_RESERVED,
> +	BAR_DISABLED,
>  	BAR_64BIT_UPPER,
>  };
>
> @@ -238,7 +246,7 @@ struct pci_epc_bar_rsvd_region {
>   *
>   *		only_64bit should not be set on a BAR of type BAR_RESERVED.
>   *		(If BARx is a 64-bit BAR that an EPF driver is not allowed to
> - *		touch, then both BARx and BARx+1 must be set to type
> + *		reprogram, then both BARx and BARx+1 must be set to type
>   *		BAR_RESERVED.)
>   * @nr_rsvd_regions: number of fixed subregions described for BAR_RESERVED
>   * @rsvd_regions: fixed subregions behind BAR_RESERVED
> --
> 2.53.0
>