kerneldevice,generic: implement ATTRS matching for any attribute

Until now we did not support ATTRS{} matches against attributes we
don't support in the core codebase. Implement now a simple lookup
mechanism which traverses the tree of sysfs path from the port sysfs
path to the physical device sysfs path, looking up the attribute
requested.

This is not completely equivalent to what udev does, because the udev
rules matching ATTRS would usually also include an additional previous
matching e.g. SUBSYSTEMS and such, so that the ATTRS is looked up
exactly in the device that also matches the additional previous
rules. In our case, we just simplify the logic and return the first
one found.

1 files changed, 36 insertions, 2 deletions

diff --git a/src/kerneldevice/mm-kernel-device-generic.c b/src/kerneldevice/mm-kernel-device-generic.c
index e6e69b67..3b9956b2 100644
--- a/src/kerneldevice/mm-kernel-device-generic.c
+++ b/src/kerneldevice/mm-kernel-device-generic.c
@@ -123,6 +123,36 @@ read_sysfs_attribute_link_basename (const gchar *path,
     return g_path_get_basename (canonicalized_path);
 }
 
+static gchar *
+lookup_sysfs_attribute_as_string (MMKernelDeviceGeneric *self,
+                                  const gchar           *attribute)
+{
+    g_autofree gchar *iter = NULL;
+
+    /* if there is no parent sysfs path set, we look for the attribute
+     * only in the port sysfs path */
+    if (!self->priv->physdev_sysfs_path)
+        return read_sysfs_attribute_as_string (self->priv->sysfs_path, attribute);
+
+    iter = g_strdup (self->priv->sysfs_path);
+    while (iter) {
+        g_autofree gchar *parent = NULL;
+        gchar            *value;
+
+        /* return first one found */
+        if ((value = read_sysfs_attribute_as_string (iter, attribute)) != NULL)
+            return value;
+
+        if (g_strcmp0 (iter, self->priv->physdev_sysfs_path) == 0)
+            break;
+        parent = g_path_get_dirname (iter);
+        g_clear_pointer (&iter, g_free);
+        iter = g_steal_pointer (&parent);
+    }
+
+    return NULL;
+}
+
 /*****************************************************************************/
 /* Load contents */
 
@@ -780,8 +810,12 @@ check_condition (MMKernelDeviceGeneric *self,
         else if (g_str_equal (attribute, "bInterfaceNumber"))
             result = (g_str_equal (match->value, "?*") || ((mm_get_uint_from_hex_str (match->value, &val)) &&
                                                            ((self->priv->interface_number == val) == condition_equal)));
-        else
-            mm_obj_warn (self, "unknown attribute: %s", attribute);
+        else {
+            g_autofree gchar *found_value = NULL;
+
+            found_value = lookup_sysfs_attribute_as_string (self, attribute);
+            result = ((found_value && g_str_equal (found_value, match->value)) == condition_equal);
+        }
 
         g_free (contents);
         g_free (attribute);