linux-kernel - [PATCH 1/3] PCI: host-common: Add an API to check for any device under the Root Ports

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Message-ID: <20251106061326.8241-2-manivannan.sadhasivam@oss.qualcomm.com>
Date: Thu,  6 Nov 2025 11:43:24 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
To: lpieralisi@...nel.org, kwilczynski@...nel.org, mani@...nel.org,
        bhelgaas@...gle.com
Cc: will@...nel.org, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        robh@...nel.org, linux-arm-msm@...r.kernel.org,
        zhangsenchuan@...incomputing.com,
        Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
Subject: [PATCH 1/3] PCI: host-common: Add an API to check for any device under the Root Ports

Some controller drivers need to check if there is any device available
under the Root Ports. So add an API that returns 'true' if a device is
found under any of the Root Ports, 'false' otherwise.

Controller drivers can use this API for usecases like turning off the
controller resources only if there are no devices under the Root Ports,
skipping PME_Turn_Off broadcast etc...

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
---
 drivers/pci/controller/pci-host-common.c | 21 +++++++++++++++++++++
 drivers/pci/controller/pci-host-common.h |  2 ++
 2 files changed, 23 insertions(+)

diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c
index 810d1c8de24e..6b4f90903dc6 100644
--- a/drivers/pci/controller/pci-host-common.c
+++ b/drivers/pci/controller/pci-host-common.c
@@ -17,6 +17,27 @@
 
 #include "pci-host-common.h"
 
+/**
+ * pci_root_ports_have_device - Check if the Root Ports under the Root bus have
+ *				any device underneath
+ * @dev: Root bus
+ *
+ * Return: true if a device is found, false otherwise
+ */
+bool pci_root_ports_have_device(struct pci_bus *root_bus)
+{
+	struct pci_bus *child;
+
+	/* Iterate over the Root Port busses and look for any device */
+	list_for_each_entry(child, &root_bus->children, node) {
+		if (list_count_nodes(&child->devices))
+			return true;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(pci_root_ports_have_device);
+
 static void gen_pci_unmap_cfg(void *ptr)
 {
 	pci_ecam_free((struct pci_config_window *)ptr);
diff --git a/drivers/pci/controller/pci-host-common.h b/drivers/pci/controller/pci-host-common.h
index 51c35ec0cf37..ff1c2ff98043 100644
--- a/drivers/pci/controller/pci-host-common.h
+++ b/drivers/pci/controller/pci-host-common.h
@@ -19,4 +19,6 @@ void pci_host_common_remove(struct platform_device *pdev);
 
 struct pci_config_window *pci_host_common_ecam_create(struct device *dev,
 	struct pci_host_bridge *bridge, const struct pci_ecam_ops *ops);
+
+bool pci_root_ports_have_device(struct pci_bus *root_bus);
 #endif
-- 
2.48.1