[PATCH v5 08/23] libxl: generalise 'driver_path' xenstore access functions in libxl_pci.c

[Paul Durrant <paul@xen.org>]

From: Paul Durrant <pdurrant@amazon.com>

For the purposes of re-binding a device to its previous driver
libxl__device_pci_assignable_add() writes the driver path into xenstore.
This path is then read back in libxl__device_pci_assignable_remove().

The functions that support this writing to and reading from xenstore are
currently dedicated for this purpose and hence the node name 'driver_path'
is hard-coded. This patch generalizes these utility functions and passes
'driver_path' as an argument. Subsequent patches will invoke them to
access other nodes.

NOTE: Because functions will have a broader use (other than storing a
      driver path in lieu of pciback) the base xenstore path is also
      changed from '/libxl/pciback' to '/libxl/pci'.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
Cc: Ian Jackson <iwj@xenproject.org>
Cc: Wei Liu <wl@xen.org>
---
 tools/libs/light/libxl_pci.c | 66 +++++++++++++++++-------------------
 1 file changed, 32 insertions(+), 34 deletions(-)

diff --git a/tools/libs/light/libxl_pci.c b/tools/libs/light/libxl_pci.c
index 31eaa95923c4..57cf6ffc85de 100644
--- a/tools/libs/light/libxl_pci.c
+++ b/tools/libs/light/libxl_pci.c
@@ -737,48 +737,46 @@ static int pciback_dev_unassign(libxl__gc *gc, libxl_device_pci *pci)
     return 0;
 }
 
-#define PCIBACK_INFO_PATH "/libxl/pciback"
+#define PCI_INFO_PATH "/libxl/pci"
 
-static void pci_assignable_driver_path_write(libxl__gc *gc,
-                                            libxl_device_pci *pci,
-                                            char *driver_path)
+static char *pci_info_xs_path(libxl__gc *gc, libxl_device_pci *pci,
+                              const char *node)
 {
-    char *path;
+    return node ?
+        GCSPRINTF(PCI_INFO_PATH"/"PCI_BDF_XSPATH"/%s",
+                  pci->domain, pci->bus, pci->dev, pci->func,
+                  node) :
+        GCSPRINTF(PCI_INFO_PATH"/"PCI_BDF_XSPATH,
+                  pci->domain, pci->bus, pci->dev, pci->func);
+}
 
-    path = GCSPRINTF(PCIBACK_INFO_PATH"/"PCI_BDF_XSPATH"/driver_path",
-                     pci->domain,
-                     pci->bus,
-                     pci->dev,
-                     pci->func);
-    if ( libxl__xs_printf(gc, XBT_NULL, path, "%s", driver_path) < 0 ) {
-        LOGE(WARN, "Write of %s to node %s failed.", driver_path, path);
+
+static void pci_info_xs_write(libxl__gc *gc, libxl_device_pci *pci,
+                              const char *node, const char *val)
+{
+    char *path = pci_info_xs_path(gc, pci, node);
+
+    if ( libxl__xs_printf(gc, XBT_NULL, path, "%s", val) < 0 ) {
+        LOGE(WARN, "Write of %s to node %s failed.", val, path);
     }
 }
 
-static char * pci_assignable_driver_path_read(libxl__gc *gc,
-                                              libxl_device_pci *pci)
+static char *pci_info_xs_read(libxl__gc *gc, libxl_device_pci *pci,
+                              const char *node)
 {
-    return libxl__xs_read(gc, XBT_NULL,
-                          GCSPRINTF(
-                           PCIBACK_INFO_PATH "/" PCI_BDF_XSPATH "/driver_path",
-                           pci->domain,
-                           pci->bus,
-                           pci->dev,
-                           pci->func));
+    char *path = pci_info_xs_path(gc, pci, node);
+
+    return libxl__xs_read(gc, XBT_NULL, path);
 }
 
-static void pci_assignable_driver_path_remove(libxl__gc *gc,
-                                              libxl_device_pci *pci)
+static void pci_info_xs_remove(libxl__gc *gc, libxl_device_pci *pci,
+                               const char *node)
 {
+    char *path = pci_info_xs_path(gc, pci, node);
     libxl_ctx *ctx = libxl__gc_owner(gc);
 
     /* Remove the xenstore entry */
-    xs_rm(ctx->xsh, XBT_NULL,
-          GCSPRINTF(PCIBACK_INFO_PATH "/" PCI_BDF_XSPATH,
-                    pci->domain,
-                    pci->bus,
-                    pci->dev,
-                    pci->func) );
+    xs_rm(ctx->xsh, XBT_NULL, path);
 }
 
 static int libxl__device_pci_assignable_add(libxl__gc *gc,
@@ -824,9 +822,9 @@ static int libxl__device_pci_assignable_add(libxl__gc *gc,
     /* Store driver_path for rebinding to dom0 */
     if ( rebind ) {
         if ( driver_path ) {
-            pci_assignable_driver_path_write(gc, pci, driver_path);
+            pci_info_xs_write(gc, pci, "driver_path", driver_path);
         } else if ( (driver_path =
-                     pci_assignable_driver_path_read(gc, pci)) != NULL ) {
+                     pci_info_xs_read(gc, pci, "driver_path")) != NULL ) {
             LOG(INFO, PCI_BDF" not bound to a driver, will be rebound to %s",
                 dom, bus, dev, func, driver_path);
         } else {
@@ -834,7 +832,7 @@ static int libxl__device_pci_assignable_add(libxl__gc *gc,
                 dom, bus, dev, func);
         }
     } else {
-        pci_assignable_driver_path_remove(gc, pci);
+        pci_info_xs_remove(gc, pci, "driver_path");
     }
 
     if ( pciback_dev_assign(gc, pci) ) {
@@ -884,7 +882,7 @@ static int libxl__device_pci_assignable_remove(libxl__gc *gc,
     }
 
     /* Rebind if necessary */
-    driver_path = pci_assignable_driver_path_read(gc, pci);
+    driver_path = pci_info_xs_read(gc, pci, "driver_path");
 
     if ( driver_path ) {
         if ( rebind ) {
@@ -897,7 +895,7 @@ static int libxl__device_pci_assignable_remove(libxl__gc *gc,
                 return -1;
             }
 
-            pci_assignable_driver_path_remove(gc, pci);
+            pci_info_xs_remove(gc, pci, "driver_path");
         }
     } else {
         if ( rebind ) {
-- 
2.20.1