Fix directory listing for /dev subdirectories

read_driver_parent_directory() was generating paths without a leading
'/' (e.g. "dmgpio8/") while DMVFS passes paths with a leading '/'
(e.g. "/dmgpio8"). This caused all path comparisons in is_directory()
and related functions to fail, resulting in:

  dmdevfs: [ERROR] Directory not found: /dmgpio8
  dmdevfs: [ERROR] File not found: /dmgpio8

Fix:
- read_driver_parent_directory: add leading '/' to non-root parent
  paths ("/%s%u/" and "/%sx/" instead of "%s%u/" and "%sx/")
- read_next_subdir_name: when listing from root '/', skip the leading
  '/' now present in full_path before extracting the next component

Co-authored-by: JohnAmadis <17320783+JohnAmadis@users.noreply.github.com>

Author: Copilot

src/dmdevfs.c

@@ -1161,16 +1161,16 @@ static void read_dir_name_from_path(const char* path, char* dir_name, size_t nam
 
 /**
  * @brief Extract the first path component of full_path that comes after base_path
- * @param base_path The directory currently being listed (e.g., "/" or "foo/")
- * @param full_path The driver's parent directory path (e.g., "foo/bar/")
+ * @param base_path The directory currently being listed (e.g., "/" or "/foo")
+ * @param full_path The driver's parent directory path (e.g., "/foo/bar/")
  * @param dir_name  Output buffer for the immediate subdirectory name
  * @param name_size Size of the output buffer
  *
  * Examples:
- * - base="/",      full="dmgpio8/"   -> "dmgpio8"
- * - base="/",      full="a/b/c/"     -> "a"
- * - base="a/",     full="a/b/c/"     -> "b"
- * - base="a/b/",   full="a/b/c/"     -> "c"
+ * - base="/",       full="/dmgpio8/"   -> "dmgpio8"
+ * - base="/",       full="/a/b/c/"     -> "a"
+ * - base="/a",      full="/a/b/c/"     -> "b"
+ * - base="/a/b",    full="/a/b/c/"     -> "c"
  */
 static void read_next_subdir_name(const char* base_path, const char* full_path, char* dir_name, size_t name_size)
 {
@@ -1193,8 +1193,8 @@ static void read_next_subdir_name(const char* base_path, const char* full_path,
     const char* start;
     if (base_len == 1 && base_path[0] == '/')
     {
-        // Base is the root directory; full_path has no leading slash
-        start = full_path;
+        // Base is the root directory; skip the leading '/' in full_path if present
+        start = (full_path[0] == '/') ? full_path + 1 : full_path;
     }
     else
     {
@@ -1327,11 +1327,11 @@ static int read_driver_parent_directory( const driver_node_t* node, char* path_b
     bool minor_given = (node->dev_num.flags & DMDRVI_NUM_MINOR) != 0;
     if(major_given && minor_given)
     {
-        Dmod_SnPrintf(path_buffer, buffer_size, "%s%u/", driver_name, node->dev_num.major);
+        Dmod_SnPrintf(path_buffer, buffer_size, "/%s%u/", driver_name, node->dev_num.major);
     }
     else if(minor_given)
     {
-        Dmod_SnPrintf(path_buffer, buffer_size, "%sx/", driver_name);
+        Dmod_SnPrintf(path_buffer, buffer_size, "/%sx/", driver_name);
     }
     else 
     {