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From:   Alistair Francis <alistair23@gmail.com>
To:     bhelgaas@google.com, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     alistair23@gmail.com, Alistair Francis <alistair.francis@wdc.com>
Subject: [PATCH] PCI/DOE: Expose the DOE protocols via sysfs
Date:   Tue, 25 Jul 2023 13:57:55 +1000
Message-Id: <20230725035755.2621507-1-alistair.francis@wdc.com>
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The PCIe 6 specification added support for the Data Object Exchange (DOE).
When DOE is supported the Discovery Data Object Protocol must be
implemented. The protocol allows a requester to obtain information about
the other DOE protocols supported by the device.

The kernel is already querying the DOE protocols supported and cacheing
the values. This patch exposes the values via sysfs. This will allow
userspace to determine which DOE protocols are supported by the PCIe
device.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
 drivers/pci/doe.c       | 28 ++++++++++++++++++++++++++++
 drivers/pci/pci-sysfs.c | 27 +++++++++++++++++++++++++++
 include/linux/pci-doe.h |  2 ++
 3 files changed, 57 insertions(+)

diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
index 1b97a5ab71a9..cc1c23c78ac1 100644
--- a/drivers/pci/doe.c
+++ b/drivers/pci/doe.c
@@ -563,6 +563,34 @@ static bool pci_doe_supports_prot(struct pci_doe_mb *doe_mb, u16 vid, u8 type)
 	return false;
 }
 
+/**
+ * pci_doe_sysfs_proto_supports() - Write the supported DOE protocols
+ *			     to a sysfs buffer
+ * @doe_mb: DOE mailbox capability to query
+ * @buf: buffer to store the sysfs strings
+ * @offset: offset in buffer to store the sysfs strings
+ *
+ * RETURNS: The number of bytes written, 0 means an error occured
+ */
+unsigned long pci_doe_sysfs_proto_supports(struct pci_doe_mb *doe_mb,
+					   char *buf, ssize_t offset)
+{
+	unsigned long index;
+	ssize_t ret = offset, r;
+	void *entry;
+
+	xa_for_each(&doe_mb->prots, index, entry) {
+		r = sysfs_emit_at(buf, ret, "0x%08lX\n", xa_to_value(entry));
+
+		if (r == 0)
+			return 0;
+
+		ret += r;
+	}
+
+	return ret;
+}
+
 /**
  * pci_doe_submit_task() - Submit a task to be processed by the state machine
  *
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index ab32a91f287b..df93051e65bf 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -16,6 +16,7 @@
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/pci.h>
+#include <linux/pci-doe.h>
 #include <linux/stat.h>
 #include <linux/export.h>
 #include <linux/topology.h>
@@ -290,6 +291,29 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(modalias);
 
+#ifdef CONFIG_PCI_DOE
+static ssize_t doe_proto_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct pci_dev *pci_dev = to_pci_dev(dev);
+	unsigned long index;
+	ssize_t ret = 0, r;
+	struct pci_doe_mb *doe_mb;
+
+	xa_for_each(&pci_dev->doe_mbs, index, doe_mb) {
+		r = pci_doe_sysfs_proto_supports(doe_mb, buf, ret);
+
+		if (r == 0)
+			return 0;
+
+		ret += r;
+	}
+
+	return ret;
+}
+static DEVICE_ATTR_RO(doe_proto);
+#endif
+
 static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
 			     const char *buf, size_t count)
 {
@@ -603,6 +627,9 @@ static struct attribute *pci_dev_attrs[] = {
 	&dev_attr_local_cpus.attr,
 	&dev_attr_local_cpulist.attr,
 	&dev_attr_modalias.attr,
+#ifdef CONFIG_PCI_DOE
+	&dev_attr_doe_proto.attr,
+#endif
 #ifdef CONFIG_NUMA
 	&dev_attr_numa_node.attr,
 #endif
diff --git a/include/linux/pci-doe.h b/include/linux/pci-doe.h
index 1f14aed4354b..066494a4dba3 100644
--- a/include/linux/pci-doe.h
+++ b/include/linux/pci-doe.h
@@ -21,5 +21,7 @@ struct pci_doe_mb *pci_find_doe_mailbox(struct pci_dev *pdev, u16 vendor,
 int pci_doe(struct pci_doe_mb *doe_mb, u16 vendor, u8 type,
 	    const void *request, size_t request_sz,
 	    void *response, size_t response_sz);
+unsigned long pci_doe_sysfs_proto_supports(struct pci_doe_mb *doe_mb,
+					   char *buf, ssize_t offset);
 
 #endif
-- 
2.40.1