Allow the filter device type to be omitted, to match any device type.

* libguile-udev/udev-monitor-func.c (udev-monitor-add-filter!): Adjust
definition and doc to make the last argument, DEVTYPE, optional.
* doc/guile-udev.texi (API Reference) <udev-monitor-add-filter!>: Document it.
<make-udev-monitor>: Adjust documentation.
* modules/udev/monitor.scm (make-udev-monitor): Add doc string.

doc/guile-udev.texi

@@ -198,8 +198,9 @@ Default value: @code{(const #f)}
 Udev event filter.
 
 Expected type: a list with two elements: the first element is the subsystem
-name, while the second element is the device type.  If needed, more filters
-can be installed via the @code{udev-monitor-add-filter!} procedure.
+name, while the second element is the device type.  To match @emph{any} device
+type, you may use @code{#f} instead of an actual device type.  If needed, more
+filters can be installed via the @code{udev-monitor-add-filter!} procedure.
 
 Default value: @code{#f}
 
@@ -240,9 +241,12 @@ Check if @var{x} is an udev-monitor object. Return @code{#t} if it is, or
 @code{#f} otherwise.
 @end deffn
 
-@deffn {Scheme Procedure} udev-monitor-add-filter! udev-monitor sybsystem devtype
+@deffn {Scheme Procedure} udev-monitor-add-filter! udev-monitor subsystem [devtype]
 Add a new filter for the events on @var{udev-monitor} that will trigger the
-provided callback. This procedure must be called before starting the scanning.
+provided callback, for a device of type @var{devtype} belonging to the
+@var{subsystem} subsystem.  @var{devtype} is optional; when omitted, devices
+of @emph{any} type are matched.  This procedure must be called before starting
+the scanning.
 @end deffn
 
 @deffn {Scheme Procedure} udev-monitor-remove-filters! udev-monitor

libguile-udev/udev-monitor-func.c

@@ -30,9 +30,11 @@
 #include "udev-device-type.h"
 #include "error.h"
 
-SCM_DEFINE_N(gudev_add_filter_x, "udev-monitor-add-filter!", 3,
-             (SCM udev_monitor, SCM subsystem, SCM devtype),
-             "Add a filter to the monitor.")
+SCM_DEFINE(gudev_add_filter_x, "udev-monitor-add-filter!", 2, 1, 0,
+           (SCM udev_monitor, SCM subsystem, SCM devtype),
+           "Add a filter to the monitor.  @var{subsystem} is the subsystem\n"
+	   "associated with a device while @var{devtype} is its device type.\n"
+	   "The @var{devtype} argument is optional.")
 #define FUNC_NAME s_gudev_add_filter_x
 {
     char* c_subsystem = NULL;
@@ -41,14 +43,17 @@ SCM_DEFINE_N(gudev_add_filter_x, "udev-monitor-add-filter!", 3,
     int result;
 
     SCM_ASSERT(scm_is_string(subsystem), subsystem, SCM_ARG1, FUNC_NAME);
-    SCM_ASSERT(scm_is_string(devtype),   devtype,   SCM_ARG2, FUNC_NAME);
+    SCM_ASSERT(scm_is_string(devtype) || SCM_UNBNDP(devtype), devtype,
+	       SCM_ARG2, FUNC_NAME);
 
     scm_dynwind_begin(0);
 
     c_subsystem = scm_to_locale_string(subsystem);
     scm_dynwind_free(c_subsystem);
 
-    c_devtype   = scm_to_locale_string(devtype);
+    if (!SCM_UNBNDP(devtype))
+        c_devtype = scm_to_locale_string(devtype);
+
     scm_dynwind_free(c_devtype);
 
     result = udev_monitor_filter_add_match_subsystem_devtype(umd->udev_monitor,

modules/udev/monitor.scm

@@ -24,12 +24,21 @@
                             (filter       #f)
                             (timeout-usec 0)
                             (timeout-sec  0))
+  "Create a new 'udev-monitor' object configured with the specified parameters.
+CALLBACK is a one argument procedure (receiving a 'udev-device' object) called
+when an event matching the specified FILTER.  FILTER is a list whose first
+element is the device subsystem, and whose second argument is the device type,
+or #f to match any type."
   (let ((monitor (%make-udev-monitor udev)))
     (udev-monitor-set-timeout!  monitor timeout-sec timeout-usec)
     (udev-monitor-set-callback! monitor callback)
     (udev-monitor-set-error-callback! monitor callback)
     (when filter
-      (udev-monitor-add-filter! monitor (car filter) (cadr filter)))
+      (let ((subsystem (car filter))
+            (devtype (cadr filter)))
+        (if devtype
+            (udev-monitor-add-filter! monitor subsystem devtype)
+            (udev-monitor-add-filter! monitor subsystem))))
     monitor))
 
 (load-extension "libguile-udev" "init_udev_monitor")