linux-kernel - [PATCH 1/3] PCI: Establish document for PCI host bridge sysfs attributes

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Message-ID: <20250716160835.680486-2-dan.j.williams@intel.com>
Date: Wed, 16 Jul 2025 09:08:33 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: <bhelgaas@...gle.com>
CC: <linux-pci@...r.kernel.org>, <lukas@...ner.de>,
	<linux-kernel@...r.kernel.org>, <Jonathan.Cameron@...wei.com>
Subject: [PATCH 1/3] PCI: Establish document for PCI host bridge sysfs attributes

In preparation for adding more host bridge sysfs attributes, document the
existing naming format and 'firmware_node' attribute.

Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 .../ABI/testing/sysfs-devices-pci-host-bridge | 19 +++++++++++++++++++
 MAINTAINERS                                   |  1 +
 2 files changed, 20 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-devices-pci-host-bridge

diff --git a/Documentation/ABI/testing/sysfs-devices-pci-host-bridge b/Documentation/ABI/testing/sysfs-devices-pci-host-bridge
new file mode 100644
index 000000000000..8c3a652799f1
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-pci-host-bridge
@@ -0,0 +1,19 @@
+What:		/sys/devices/pciDDDD:BB
+		/sys/devices/.../pciDDDD:BB
+Contact:	linux-pci@...r.kernel.org
+Description:
+		A PCI host bridge device parents a PCI bus device topology. PCI
+		controllers may also parent host bridges. The DDDD:BB format
+		conveys the PCI domain (ACPI segment) number and root bus number
+		(in hexadecimal) of the host bridge. Note that the domain number
+		may be larger than the 16-bits that the "DDDD" format implies
+		for emulated host-bridges.
+
+What:		pciDDDD:BB/firmware_node
+Contact:	linux-pci@...r.kernel.org
+Description:
+		(RO) Symlink to the platform firmware device object "companion"
+		of the host bridge. For example, an ACPI device with an _HID of
+		PNP0A08 (/sys/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00). See
+		/sys/devices/pciDDDD:BB entry for details about the DDDD:BB
+		format.
diff --git a/MAINTAINERS b/MAINTAINERS
index 0c1d245bf7b8..368ca0bfdb9f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19198,6 +19198,7 @@ Q:	https://patchwork.kernel.org/project/linux-pci/list/
 B:	https://bugzilla.kernel.org
 C:	irc://irc.oftc.net/linux-pci
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git
+F:	Documentation/ABI/testing/sysfs-devices-pci-host-bridge
 F:	Documentation/PCI/
 F:	Documentation/devicetree/bindings/pci/
 F:	arch/x86/kernel/early-quirks.c
-- 
2.50.1