backlight: include ID_PATH in file names for backlight settings

Much like for rfkill devices we should provide some stability regarding
enumeration order, hence include the stable bits of the device path in
the file name we store settings under.

1 files changed, 26 insertions, 3 deletions

diff --git a/src/backlight/backlight.c b/src/backlight/backlight.c
index 51a67a042a..e8cdad61ed 100644
--- a/src/backlight/backlight.c
+++ b/src/backlight/backlight.c
@@ -195,8 +195,8 @@ static bool validate_device(struct udev *udev, struct udev_device *device) {
 int main(int argc, char *argv[]) {
         _cleanup_udev_unref_ struct udev *udev = NULL;
         _cleanup_udev_device_unref_ struct udev_device *device = NULL;
-        _cleanup_free_ char *saved = NULL, *ss = NULL;
-        const char *sysname;
+        _cleanup_free_ char *saved = NULL, *ss = NULL, *escaped_ss = NULL, *escaped_sysname = NULL, *escaped_path_id = NULL;
+        const char *sysname, *path_id;
         int r;
 
         if (argc != 3) {
@@ -252,7 +252,30 @@ int main(int argc, char *argv[]) {
                 return EXIT_FAILURE;
         }
 
-        saved = strjoin("/var/lib/systemd/backlight/", ss, ":", sysname, NULL);
+        escaped_ss = cescape(ss);
+        if (!escaped_ss) {
+                log_oom();
+                return EXIT_FAILURE;
+        }
+
+        escaped_sysname = cescape(sysname);
+        if (!escaped_sysname) {
+                log_oom();
+                return EXIT_FAILURE;
+        }
+
+        path_id = udev_device_get_property_value(device, "ID_PATH");
+        if (path_id) {
+                escaped_path_id = cescape(path_id);
+                if (!escaped_path_id) {
+                        log_oom();
+                        return EXIT_FAILURE;
+                }
+
+                saved = strjoin("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname, NULL);
+        } else
+                saved = strjoin("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname, NULL);
+
         if (!saved) {
                 log_oom();
                 return EXIT_FAILURE;