linux: Fix platform device probe for DT-based PCI

On a DT-base PCI platform, the sysfs path of vga device is like this:
/sys/devices/platform/bus@10000000/1a000000.pci/pci0000:00/0000:00:11.0/0000:04:00.0.

Then the ID_PATH from udev is platform-1a000000.pci-pci-0000:04:00.0 and
the BusID will be pci-0000:04:00.0, which causes Xorg start fail. This
is because config_udev_odev_setup_attribs() use strstr() to search the
first "pci-" in ID_PATH. To fix this, we implement a strrstr() function
and use it to search the last "pci-" in ID_PATH, which can get a correct
BusID.

(backported from commit 9fbd3e43)
Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Huacai Chen <chenhc@lemote.com>

config/udev.c

@@ -464,6 +464,31 @@ config_udev_fini(void)
 
 #ifdef CONFIG_UDEV_KMS
 
+/* Find the last occurrence of the needle in haystack */
+static char *strrstr(const char *haystack, const char *needle)
+{
+    char *prev, *last, *tmp;
+
+    prev = strstr(haystack, needle);
+    if (!prev)
+        return NULL;
+
+    last = prev;
+    tmp = prev + 1;
+
+    while (tmp) {
+        last = strstr(tmp, needle);
+        if (!last)
+            return prev;
+        else {
+            prev = last;
+            tmp = prev + 1;
+        }
+    }
+
+    return last;
+}
+
 static void
 config_udev_odev_setup_attribs(struct udev_device *udev_device, const char *path, const char *syspath,
                                int major, int minor,
@@ -478,7 +503,7 @@ config_udev_odev_setup_attribs(struct udev_device *udev_device, const char *path
     attribs->minor = minor;
 
     value = udev_device_get_property_value(udev_device, "ID_PATH");
-    if (value && (str = strstr(value, "pci-"))) {
+    if (value && (str = strrstr(value, "pci-"))) {
         attribs->busid = XNFstrdup(str);
         attribs->busid[3] = ':';
     }