netdev - [RFC PATCH v3 34/35] Documentation: PCI: endpoint: pci-epf-vntb: Update and add mwN

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Message-ID: <20251217151609.3162665-35-den@valinux.co.jp>
Date: Thu, 18 Dec 2025 00:16:08 +0900
From: Koichiro Den <den@...inux.co.jp>
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Subject: [RFC PATCH v3 34/35] Documentation: PCI: endpoint: pci-epf-vntb: Update and add mwN_offset usage

Add a concrete example showing how to place multiple memory windows in
the same BAR (one for data, one for interrupts) by using 'mwN_offset'
and 'mwN_bar'.

Signed-off-by: Koichiro Den <den@...inux.co.jp>
---
 Documentation/PCI/endpoint/pci-vntb-howto.rst | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/Documentation/PCI/endpoint/pci-vntb-howto.rst b/Documentation/PCI/endpoint/pci-vntb-howto.rst
index 9a7a2f0a6849..bfc3e51ab79f 100644
--- a/Documentation/PCI/endpoint/pci-vntb-howto.rst
+++ b/Documentation/PCI/endpoint/pci-vntb-howto.rst
@@ -90,9 +90,9 @@ of the function device and is populated with the following NTB specific
 attributes that can be configured by the user::
 
 	# ls functions/pci_epf_vntb/func1/pci_epf_vntb.0/
-	ctrl_bar  db_count  mw1_bar  mw2_bar  mw3_bar  mw4_bar	spad_count
-	db_bar	  mw1	    mw2      mw3      mw4      num_mws	vbus_number
-	vntb_vid  vntb_pid
+	ctrl_bar  mw1         mw2         mw3         mw4         num_mws      vntb_pid
+	db_bar    mw1_bar     mw2_bar     mw3_bar     mw4_bar     spad_count   vntb_vid
+	db_count  mw1_offset  mw2_offset  mw3_offset  mw4_offset  vbus_number
 
 A sample configuration for NTB function is given below::
 
@@ -111,6 +111,16 @@ A sample configuration for virtual NTB driver for virtual PCI bus::
 	# echo 0x080A > functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_pid
 	# echo 0x10 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/vbus_number
 
+When BAR resources are tight but you still need to create many memory
+windows, you can pack multiple windows into a single BAR via 'mwN_offset'
+and 'mwN_bar' as shown below::
+
+	# echo 0xE0000 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw1
+	# echo 0x20000 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw2
+	# echo 0xE0000 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw2_offset
+	# echo 2 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw1_bar
+	# echo 2 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw2_bar
+
 Binding pci-epf-ntb Device to EP Controller
 --------------------------------------------
 
-- 
2.51.0