linux-kernel - [PATCH v3 08/10] PCI: Add pci_find_dvsec

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Date:   Sat, 09 Oct 2021 09:44:39 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     linux-cxl@...r.kernel.org
Cc:     "David E. Box" <david.e.box@...ux.intel.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Ben Widawsky <ben.widawsky@...el.com>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, hch@....de
Subject: [PATCH v3 08/10] PCI: Add pci_find_dvsec_capability to find
 designated VSEC

From: Ben Widawsky <ben.widawsky@...el.com>

Add pci_find_dvsec_capability to locate a Designated Vendor-Specific
Extended Capability with the specified Vendor ID and Capability ID.

The Designated Vendor-Specific Extended Capability (DVSEC) allows one or
more "vendor" specific capabilities that are not tied to the Vendor ID
of the PCI component. Where the DVSEC Vendor may be a standards body
like CXL.

Cc: David E. Box <david.e.box@...ux.intel.com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: linux-pci@...r.kernel.org
Cc: linuxppc-dev@...ts.ozlabs.org
Cc: Andrew Donnellan <ajd@...ux.ibm.com>
Cc: Lu Baolu <baolu.lu@...ux.intel.com>
Reviewed-by: Frederic Barrat <fbarrat@...ux.ibm.com>
Signed-off-by: Ben Widawsky <ben.widawsky@...el.com>
Reviewed-by: Andrew Donnellan <ajd@...ux.ibm.com>
Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
Tested-by: Kan Liang <kan.liang@...ux.intel.com>
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 drivers/pci/pci.c   |   32 ++++++++++++++++++++++++++++++++
 include/linux/pci.h |    1 +
 2 files changed, 33 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index ce2ab62b64cf..94ac86ff28b0 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -732,6 +732,38 @@ u16 pci_find_vsec_capability(struct pci_dev *dev, u16 vendor, int cap)
 }
 EXPORT_SYMBOL_GPL(pci_find_vsec_capability);
 
+/**
+ * pci_find_dvsec_capability - Find DVSEC for vendor
+ * @dev: PCI device to query
+ * @vendor: Vendor ID to match for the DVSEC
+ * @dvsec: Designated Vendor-specific capability ID
+ *
+ * If DVSEC has Vendor ID @vendor and DVSEC ID @dvsec return the capability
+ * offset in config space; otherwise return 0.
+ */
+u16 pci_find_dvsec_capability(struct pci_dev *dev, u16 vendor, u16 dvsec)
+{
+	int pos;
+
+	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DVSEC);
+	if (!pos)
+		return 0;
+
+	while (pos) {
+		u16 v, id;
+
+		pci_read_config_word(dev, pos + PCI_DVSEC_HEADER1, &v);
+		pci_read_config_word(dev, pos + PCI_DVSEC_HEADER2, &id);
+		if (vendor == v && dvsec == id)
+			return pos;
+
+		pos = pci_find_next_ext_capability(dev, pos, PCI_EXT_CAP_ID_DVSEC);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pci_find_dvsec_capability);
+
 /**
  * pci_find_parent_resource - return resource region of parent bus of given
  *			      region
diff --git a/include/linux/pci.h b/include/linux/pci.h
index cd8aa6fce204..c93ccfa4571b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1130,6 +1130,7 @@ u16 pci_find_ext_capability(struct pci_dev *dev, int cap);
 u16 pci_find_next_ext_capability(struct pci_dev *dev, u16 pos, int 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);
+u16 pci_find_dvsec_capability(struct pci_dev *dev, u16 vendor, u16 dvsec);
 
 u64 pci_get_dsn(struct pci_dev *dev);