[WIP PATCH v3 7/7] PCI: endpoint: pci-epf-ntb: Document EPF-owned MSI-X layout

[Koichiro Den]

pci-epf-ntb reads host-programmed MSI-X Table entries through epf_bar[]
to set up peer outbound mappings. A hardware-owned Table does not have
that backing.

Document why pci-epf-ntb keeps its Table and PBA in EPF-owned memory
instead of selecting a hardware-owned layout like the other converted
EPF drivers.

Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
---
Changes in v3:
  - New patch.
---
 drivers/pci/endpoint/functions/pci-epf-ntb.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/pci/endpoint/functions/pci-epf-ntb.c b/drivers/pci/endpoint/functions/pci-epf-ntb.c
index f3e0e1b3ffb9..adef3b9dc2fc 100644
--- a/drivers/pci/endpoint/functions/pci-epf-ntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-ntb.c
@@ -1031,6 +1031,12 @@ static int epf_ntb_config_spad_bar_alloc(struct epf_ntb *ntb,
 	ctrl_size = sizeof(struct epf_ntb_ctrl);
 	spad_size = spad_count * 4;
 
+	/*
+	 * Keep the MSI-X Table and PBA in EPF-owned memory.
+	 * epf_ntb_configure_msix() reads host-programmed Table entries through
+	 * epf_bar[] to set up peer outbound mappings. A hardware-owned Table has
+	 * no such backing.
+	 */
 	msix_capable = epc_features->msix_capable;
 	if (msix_capable) {
 		msix_table_size = PCI_MSIX_ENTRY_SIZE * ntb->db_count;
-- 
2.51.0

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Best regards,
Koichiro

> 
> 
> Kind regards,
> Niklas