Allow the device name to be passed to linuxaudiodev.open(), for

consistency with the built-in open() (and every other sane open()
function, for that matter).  The two valid ways to call this open() are
now open(mode) and open(device, mode).

For backwards compatibility, retain the old open(mode) calling syntax --
this makes the error message when you call open(device) a bit confusing,
but oh well.

This is the first half of SF patch #644977.

Modules/linuxaudiodev.c

@@ -79,11 +79,21 @@ newladobject(PyObject *arg)
 {
     lad_t *xp;
     int fd, afmts, imode;
-    char *mode;
-    char *basedev;
+    char *basedev = NULL;
+    char *mode = NULL;
+
+    /* Two ways to call linuxaudiodev.open():
+         open(device, mode) (for consistency with builtin open())
+         open(mode)         (for backwards compatibility)
+       because the *first* argument is optional, parsing args is
+       a wee bit tricky. */
+    if (!PyArg_ParseTuple(arg, "s|s:open", &basedev, &mode))
+       return NULL;
+    if (mode == NULL) {                 /* only one arg supplied */
+       mode = basedev;
+       basedev = NULL;
+    }
 
-    /* Check arg for r/w/rw */
-    if (!PyArg_ParseTuple(arg, "s:open", &mode)) return NULL;
     if (strcmp(mode, "r") == 0)
         imode = O_RDONLY;
     else if (strcmp(mode, "w") == 0)
@@ -102,9 +112,11 @@ newladobject(PyObject *arg)
      * latter uses 8-bit unsigned encoding.
      */
 
-    basedev = getenv("AUDIODEV");
-    if (!basedev)
-        basedev = "/dev/dsp";
+    if (basedev == NULL) {              /* called with one arg */
+       basedev = getenv("AUDIODEV");
+       if (basedev == NULL)             /* $AUDIODEV not set */
+          basedev = "/dev/dsp";
+    }
 
     if ((fd = open(basedev, imode)) == -1) {
         PyErr_SetFromErrnoWithFilename(LinuxAudioError, basedev);