services: dbus: Add rtkit service.

* gnu/services/dbus.scm (rtkit-service-type): New variable.
(rtkit-configuration): New record.

Change-Id: I5078cb5032824c7799e7d26962911bbc67527562
Signed-off-by: Liliana Marie Prikler <liliana.prikler@gmail.com>

doc/guix.texi

@@ -27860,6 +27860,23 @@ Log level to output logs. Possible values: @samp{"silent"}, @samp{"error"},
 @end table
 @end deftp
 
+@defvar rtkit-service-type
+Type for the service that allows D-Bus to start the RealtimeKit D-Bus
+service. The RTKit service provides a system D-Bus interface for user
+processes, such as PipeWire, to securely use realtime scheduling.
+
+The value for this service is a @code{<rtkit-configuration>} object.
+@end defvar
+
+@deftp {Data Type} rtkit-configuration
+Data type representing the configuration for @code{rtkit-service-type}.
+
+@table @asis
+@item @code{rtkit} (default: @code{rtkit}) (type: file-like)
+Package object for RTKit.
+
+@end table
+@end deftp
 
 @node Sound Services
 @subsection Sound Services

gnu/services/dbus.scm

@@ -29,6 +29,7 @@
   #:use-module ((gnu packages glib) #:select (dbus))
   #:use-module (gnu packages polkit)
   #:use-module (gnu packages admin)
+  #:use-module (gnu packages freedesktop)
   #:use-module (guix deprecation)
   #:use-module (guix gexp)
   #:use-module ((guix packages) #:select (package-name))
@@ -45,7 +46,10 @@
             polkit-configuration
             polkit-configuration?
             polkit-service-type
-            polkit-service))  ; deprecated
+            polkit-service  ; deprecated
+
+            rtkit-configuration
+            rtkit-service-type))  
 
 ;;;
 ;;; D-Bus.
@@ -442,4 +446,36 @@ the capability to suspend the system if the user is logged in locally."
   (service polkit-service-type
            (polkit-configuration (polkit polkit))))
 
+(define-record-type* <rtkit-configuration>
+  rtkit-configuration make-rtkit-configuration
+  rtkit-configuration?
+  (rtkit rtkit-configuration-rtkit
+         (default rtkit)))
+
+(define %rtkit-account
+  ;; Account used by rtkit.
+  (user-account
+    (name "rtkit")
+    (group "nogroup")
+    (system? #t)
+    (comment "Realtime kit user")
+    (home-directory "/var/empty")
+    (shell (file-append shadow "/sbin/nologin"))))
+
+(define rtkit-service-type
+  (let ((rtkit-package (compose list rtkit-configuration-rtkit)))
+    (service-type
+      (name 'rtkit)
+      (extensions
+       (list (service-extension
+              polkit-service-type rtkit-package)
+	     (service-extension dbus-root-service-type rtkit-package)
+	     (service-extension
+              account-service-type
+              (const (list %rtkit-account)))))
+      (default-value (rtkit-configuration))
+      (description
+       "Return a service that sets up D-Bus and PolKit so that the Realtime Kit
+daemon is readily usable."))))
+
 ;;; dbus.scm ends here