From 5714a49f14b93fc51185c6d37af101d24fc5dbd2 Mon Sep 17 00:00:00 2001
From: Ray Kinsella <mdr@ashroe.eu>
Date: Tue, 2 Nov 2021 13:33:44 +0000
Subject: [PATCH] vlib: retrieve the root bus of a given pci device

Added a function to parse sysfs, determine the root bus & domain of a given pci
device.

Type: improvement

Signed-off-by: Ray Kinsella <mdr@ashroe.eu>
Change-Id: I36778116ecaa2d591617450fe5ae0bdb46b4424b
---
 src/vlib/linux/pci.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/vlib/pci/pci.c   |  6 ++++++
 src/vlib/pci/pci.h   |  8 ++++---
 3 files changed, 70 insertions(+), 3 deletions(-)

diff --git a/src/vlib/linux/pci.c b/src/vlib/linux/pci.c
index 1e5ab67b25d..d968fe26695 100644
--- a/src/vlib/linux/pci.c
+++ b/src/vlib/linux/pci.c
@@ -55,6 +55,7 @@
 #include <linux/vfio.h>
 #include <sys/eventfd.h>
 
+#define SYSFS_DEVICES_PCI "/sys/devices/pci"
 static const char *sysfs_pci_dev_path = "/sys/bus/pci/devices";
 static const char *sysfs_pci_drv_path = "/sys/bus/pci/drivers";
 static char *sysfs_mod_vfio_noiommu =
@@ -383,6 +384,64 @@ done:
   return di;
 }
 
+clib_error_t *__attribute__ ((weak))
+vlib_pci_get_device_root_bus (vlib_pci_addr_t *addr, vlib_pci_addr_t *root_bus)
+{
+  u8 *rel_path = 0, *abs_path = 0, *link_path = 0;
+  unformat_input_t input;
+  u32 fd = open (sysfs_pci_dev_path, O_RDONLY);
+  u32 size = 0;
+  u32 domain = 0, bus;
+  clib_error_t *err = NULL;
+
+  if (fd < 0)
+    return clib_error_return_unix (0, "failed to open %s", sysfs_pci_dev_path);
+
+  vec_alloc (rel_path, PATH_MAX);
+  vec_alloc (abs_path, PATH_MAX);
+
+  link_path =
+    format (0, "%s/%U", sysfs_pci_dev_path, format_vlib_pci_addr, addr);
+  size = readlinkat (fd, (char *) link_path, (char *) rel_path, PATH_MAX);
+  if (size < 0)
+    {
+      err = clib_error_return_unix (0, "failed to read %s", rel_path);
+      goto done;
+    }
+
+  rel_path[size] = '\0';
+  vec_free (link_path);
+
+  link_path = format (0, "%s/%s", sysfs_pci_dev_path, rel_path);
+  if (!realpath ((char *) link_path, (char *) abs_path))
+    {
+      err = clib_error_return_unix (0, "failed to resolve %s", link_path);
+      goto done;
+    }
+
+  unformat_init_string (&input, (char *) abs_path,
+			clib_strnlen ((char *) abs_path, PATH_MAX));
+
+  if (!unformat (&input, SYSFS_DEVICES_PCI "%x:%x/%s", &domain, &bus,
+		 link_path))
+    {
+      err = clib_error_return (0, "unknown input '%U'", format_unformat_error,
+			       input);
+      goto done;
+    }
+
+  root_bus->domain = domain;
+  root_bus->bus = bus;
+
+done:
+  vec_free (abs_path);
+  vec_free (link_path);
+  vec_free (rel_path);
+  close (fd);
+
+  return err;
+}
+
 static int
 directory_exists (char *path)
 {
diff --git a/src/vlib/pci/pci.c b/src/vlib/pci/pci.c
index 18d93acbf08..5535eb1709c 100644
--- a/src/vlib/pci/pci.c
+++ b/src/vlib/pci/pci.c
@@ -61,6 +61,12 @@ vlib_pci_get_device_info (vlib_main_t * vm, vlib_pci_addr_t * addr,
   return 0;
 }
 
+clib_error_t *__attribute__ ((weak))
+vlib_pci_get_device_root_bus (vlib_pci_addr_t *addr, vlib_pci_addr_t *root_bus)
+{
+  return 0;
+}
+
 vlib_pci_addr_t * __attribute__ ((weak)) vlib_pci_get_all_dev_addrs ()
 {
   return 0;
diff --git a/src/vlib/pci/pci.h b/src/vlib/pci/pci.h
index 01f7d5b9669..1dc4ce6ea36 100644
--- a/src/vlib/pci/pci.h
+++ b/src/vlib/pci/pci.h
@@ -96,9 +96,11 @@ typedef struct vlib_pci_device_info
 
 typedef u32 vlib_pci_dev_handle_t;
 
-vlib_pci_device_info_t *vlib_pci_get_device_info (vlib_main_t * vm,
-						  vlib_pci_addr_t * addr,
-						  clib_error_t ** error);
+vlib_pci_device_info_t *vlib_pci_get_device_info (vlib_main_t *vm,
+						  vlib_pci_addr_t *addr,
+						  clib_error_t **error);
+clib_error_t *vlib_pci_get_device_root_bus (vlib_pci_addr_t *addr,
+					    vlib_pci_addr_t *root_bus);
 vlib_pci_addr_t *vlib_pci_get_all_dev_addrs ();
 vlib_pci_addr_t *vlib_pci_get_addr (vlib_main_t * vm,
 				    vlib_pci_dev_handle_t h);
-- 
2.16.6