[PATCH v8 2/5] PCI: endpoint: Add BAR subrange mapping support

[Koichiro Den]

On Thu, Jan 15, 2026 at 09:52:58AM -0500, Frank Li wrote:
> On Thu, Jan 15, 2026 at 05:49:25PM +0900, Koichiro Den wrote:
> > Extend the PCI endpoint core to support mapping subranges within a BAR.
> > Add an optional 'submap' field in struct pci_epf_bar so an endpoint
> > function driver can request inbound mappings that fully cover the BAR.
> >
> > Introduce a new EPC feature bit, subrange_mapping, and reject submap
> > requests from pci_epc_set_bar() unless the controller advertises both
> > subrange_mapping and dynamic_inbound_mapping features.
> >
> > The submap array describes the complete BAR layout (no overlaps and no
> > gaps are allowed to avoid exposing untranslated address ranges). This
> > provides the generic infrastructure needed to map multiple logical
> > regions into a single BAR at different offsets, without assuming a
> > controller-specific inbound address translation mechanism.
> >
> > Signed-off-by: Koichiro Den <den at valinux.co.jp>
> > ---
> >  drivers/pci/endpoint/pci-epc-core.c |  8 ++++++++
> >  include/linux/pci-epc.h             |  4 ++++
> >  include/linux/pci-epf.h             | 27 +++++++++++++++++++++++++++
> >  3 files changed, 39 insertions(+)
> >
> > diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> > index ca7f19cc973a..068155819c57 100644
> > --- a/drivers/pci/endpoint/pci-epc-core.c
> > +++ b/drivers/pci/endpoint/pci-epc-core.c
> > @@ -596,6 +596,14 @@ int pci_epc_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> >  	if (!epc_features)
> >  		return -EINVAL;
> >
> > +	if (epf_bar->num_submap && !epf_bar->submap)
> > +		return -EINVAL;
> > +
> > +	if (epf_bar->num_submap &&
> > +	    !(epc_features->dynamic_inbound_mapping &&
> > +	      epc_features->subrange_mapping))
> > +		return -EINVAL;
> > +
> >  	if (epc_features->bar[bar].type == BAR_RESIZABLE &&
> >  	    (epf_bar->size < SZ_1M || (u64)epf_bar->size > (SZ_128G * 1024)))
> >  		return -EINVAL;
> > diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> > index 4c8516756c56..c021c7af175f 100644
> > --- a/include/linux/pci-epc.h
> > +++ b/include/linux/pci-epc.h
> > @@ -227,6 +227,9 @@ struct pci_epc_bar_desc {
> >   *                           inbound mappings for an already configured BAR
> >   *                           (i.e. allow calling pci_epc_set_bar() again
> >   *                           without first calling pci_epc_clear_bar())
> > + * @subrange_mapping: indicate if the EPC device can map inbound subranges for a
> > + *                    BAR. This feature depends on @dynamic_inbound_mapping
> > + *                    feature.
> >   * @msi_capable: indicate if the endpoint function has MSI capability
> >   * @msix_capable: indicate if the endpoint function has MSI-X capability
> >   * @intx_capable: indicate if the endpoint can raise INTx interrupts
> > @@ -236,6 +239,7 @@ struct pci_epc_bar_desc {
> >  struct pci_epc_features {
> >  	unsigned int	linkup_notifier : 1;
> >  	unsigned int	dynamic_inbound_mapping : 1;
> > +	unsigned int	subrange_mapping : 1;
> >  	unsigned int	msi_capable : 1;
> >  	unsigned int	msix_capable : 1;
> >  	unsigned int	intx_capable : 1;
> > diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
> > index 48f68c4dcfa5..46f817da6e24 100644
> > --- a/include/linux/pci-epf.h
> > +++ b/include/linux/pci-epf.h
> > @@ -110,6 +110,26 @@ struct pci_epf_driver {
> >
> >  #define to_pci_epf_driver(drv) container_of_const((drv), struct pci_epf_driver, driver)
> >
> > +/**
> > + * struct pci_epf_bar_submap - BAR subrange for inbound mapping
> > + * @phys_addr: target physical/DMA address for this subrange
> > + * @size: the size of the subrange to be mapped
> > + *
> > + * When pci_epf_bar.num_submap is >0, pci_epf_bar.submap describes the
> > + * complete BAR layout. This allows an EPC driver to program multiple
> > + * inbound translation windows for a single BAR when supported by the
> > + * controller. The array order defines the BAR layout (submap[0] at offset
> > + * 0, and each immediately follows the previous one).
> > + *
> > + * Note that the subranges:
> > + * - must be non-overlapping
> > + * - must exactly cover the BAR (i.e. no holes)
> 
> It is impossible after use 'size'. It can be removed.

Agreed, those notes (ie non-overlapping/no holes) are redundant now.
Thanks for pointing it out. I'll drop them.

Koichiro

> 
> > + */
> > +struct pci_epf_bar_submap {
> > +	dma_addr_t	phys_addr;
> > +	size_t		size;
> > +};
> > +
> >  /**
> >   * struct pci_epf_bar - represents the BAR of EPF device
> >   * @phys_addr: physical address that should be mapped to the BAR
> > @@ -119,6 +139,9 @@ struct pci_epf_driver {
> >   *            requirement
> >   * @barno: BAR number
> >   * @flags: flags that are set for the BAR
> > + * @num_submap: number of entries in @submap
> > + * @submap: array of subrange descriptors allocated by the caller. See
> > + *          struct pci_epf_bar_submap for the restrictions in detail.
> >   */
> >  struct pci_epf_bar {
> >  	dma_addr_t	phys_addr;
> > @@ -127,6 +150,10 @@ struct pci_epf_bar {
> >  	size_t		mem_size;
> >  	enum pci_barno	barno;
> >  	int		flags;
> > +
> > +	/* Optional sub-range mapping */
> > +	unsigned int	num_submap;
> > +	struct pci_epf_bar_submap	*submap;
> 
> struct pci_epf_bar_submap submap[] __counted_by(num_submap);
> 
> Not sure if use this simplify alloc/free.
> 
> Frank
> >  };
> >
> >  /**
> > --
> > 2.51.0
> >