services: gpm: Provide a default value and document 'gpm-service-type'.

* gnu/services/base.scm (%default-gpm-options): New variable.
(<gpm-configuration>)[gpm, options]: Add default values.
(gpm-service-type)[default-value]: New field.
(gpm-service): Use %DEFAULT-GPM-OPTIONS and mark as deprecated.
* doc/guix.texi (Base Services): Document 'gpm-service-type' and
'gpm-configuration'.  Remove 'gpm-service'.

doc/guix.texi

@@ -10383,15 +10383,31 @@ See @code{man loadkeys} for details.
 
 @cindex mouse
 @cindex gpm
-@deffn {Scheme Procedure} gpm-service [#:gpm @var{gpm}] @
-          [#:options]
-Run @var{gpm}, the general-purpose mouse daemon, with the given
-command-line @var{options}.  GPM allows users to use the mouse in the console,
-notably to select, copy, and paste text.  The default value of @var{options}
-uses the @code{ps2} protocol, which works for both USB and PS/2 mice.
+@defvr {Scheme Variable} gpm-service-type
+This is the type of the service that runs GPM, the @dfn{general-purpose
+mouse daemon}, which provides mouse support to the Linux console.  GPM
+allows users to use the mouse in the console, notably to select, copy,
+and paste text.
 
-This service is not part of @var{%base-services}.
-@end deffn
+The value for services of this type must be a @code{gpm-configuration}
+(see below).  This service is not part of @var{%base-services}.
+@end defvr
+
+@deftp {Data Type} gpm-configuration
+Data type representing the configuration of GPM.
+
+@table @asis
+@item @code{options} (default: @code{%default-gpm-options})
+Command-line options passed to @command{gpm}.  The default set of
+options instruct @command{gpm} to listen to mouse events on
+@file{/dev/input/mice}.  @xref{Command Line,,, gpm, gpm manual}, for
+more information.
+
+@item @code{gpm} (default: @code{gpm})
+The GPM package to use.
+
+@end table
+@end deftp
 
 @anchor{guix-publish-service-type}
 @deffn {Scheme Variable} guix-publish-service-type

gnu/services/base.scm

@@ -1962,10 +1962,16 @@ extra rules from the packages listed in @var{rules}."
   "Return a service that uses @var{device} as a swap device."
   (service swap-service-type device))
 
+(define %default-gpm-options
+  ;; Default options for GPM.
+  '("-m" "/dev/input/mice" "-t" "ps2"))
+
 (define-record-type* <gpm-configuration>
   gpm-configuration make-gpm-configuration gpm-configuration?
-  (gpm      gpm-configuration-gpm)                ;package
-  (options  gpm-configuration-options))           ;list of strings
+  (gpm      gpm-configuration-gpm                 ;package
+            (default gpm))
+  (options  gpm-configuration-options             ;list of strings
+            (default %default-gpm-options)))
 
 (define gpm-shepherd-service
   (match-lambda
@@ -2000,14 +2006,15 @@ extra rules from the packages listed in @var{rules}."
                 (extensions
                  (list (service-extension shepherd-root-service-type
                                           gpm-shepherd-service)))
+                (default-value (gpm-configuration))
                 (description
                  "Run GPM, the general-purpose mouse daemon, with the given
 command-line options.  GPM allows users to use the mouse in the console,
 notably to select, copy, and paste text.  The default options use the
 @code{ps2} protocol, which works for both USB and PS/2 mice.")))
 
-(define* (gpm-service #:key (gpm gpm)
-                      (options '("-m" "/dev/input/mice" "-t" "ps2")))
+(define* (gpm-service #:key (gpm gpm)             ;deprecated
+                      (options %default-gpm-options))
   "Run @var{gpm}, the general-purpose mouse daemon, with the given
 command-line @var{options}.  GPM allows users to use the mouse in the console,
 notably to select, copy, and paste text.  The default value of @var{options}