From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Vinod Koul <vkoul@kernel.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 098/235] PCI: Add pci_find_vsec_capability() to find a specific VSEC
Date: Thu, 20 Aug 2026 16:55:34 +0200
Message-ID: <20260820145219.429100440@linuxfoundation.org>
In-Reply-To: <20260820145216.426568665@linuxfoundation.org>
References: <20260820145216.426568665@linuxfoundation.org>
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5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gustavo Pimentel <Gustavo.Pimentel@synopsys.com>

[ Upstream commit c124fd9a969acaa83f6dfa5e160a99a500af9e4b ]

Add pci_find_vsec_capability() to locate a Vendor-Specific Extended
Capability with the specified VSEC ID.

The Vendor-Specific Extended Capability (VSEC) allows one or more
proprietary capabilities defined by the vendor which aren't standard
or shared between vendors.

Signed-off-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/d89506834fb11c6fa0bd5d515c0dd55b13ac6958.1613674948.git.gustavo.pimentel@synopsys.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Stable-dep-of: 8ffba0171c6b ("dmaengine: dw-edma: Add spinlock to protect DONE_INT_MASK and ABORT_INT_MASK")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/pci/pci.c   |   30 ++++++++++++++++++++++++++++++
 include/linux/pci.h |    1 +
 2 files changed, 31 insertions(+)

--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -691,6 +691,36 @@ int pci_find_ht_capability(struct pci_de
 EXPORT_SYMBOL_GPL(pci_find_ht_capability);
 
 /**
+ * pci_find_vsec_capability - Find a vendor-specific extended capability
+ * @dev: PCI device to query
+ * @vendor: Vendor ID for which capability is defined
+ * @cap: Vendor-specific capability ID
+ *
+ * If @dev has Vendor ID @vendor, search for a VSEC capability with
+ * VSEC ID @cap. If found, return the capability offset in
+ * config space; otherwise return 0.
+ */
+u16 pci_find_vsec_capability(struct pci_dev *dev, u16 vendor, int cap)
+{
+	u16 vsec = 0;
+	u32 header;
+
+	if (vendor != dev->vendor)
+		return 0;
+
+	while ((vsec = pci_find_next_ext_capability(dev, vsec,
+						     PCI_EXT_CAP_ID_VNDR))) {
+		if (pci_read_config_dword(dev, vsec + PCI_VNDR_HEADER,
+					  &header) == PCIBIOS_SUCCESSFUL &&
+		    PCI_VNDR_HEADER_ID(header) == cap)
+			return vsec;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pci_find_vsec_capability);
+
+/**
  * pci_find_parent_resource - return resource region of parent bus of given
  *			      region
  * @dev: PCI device structure contains resources to be searched
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1101,6 +1101,7 @@ int pci_find_next_ext_capability(struct
 int pci_find_ht_capability(struct pci_dev *dev, int ht_cap);
 int pci_find_next_ht_capability(struct pci_dev *dev, int pos, int ht_cap);
 struct pci_bus *pci_find_next_bus(const struct pci_bus *from);
+u16 pci_find_vsec_capability(struct pci_dev *dev, u16 vendor, int cap);
 
 u64 pci_get_dsn(struct pci_dev *dev);