services: Improve the upower-service-type.

Add a description and default value. Switch the documentation to mention the
service-type and the configuration record, rather than the upower-service
procedure.

* gnu/services/desktop.scm (upower-service-type)[description, default-value]:
Define these fields.
(%desktop-services): Change (upower-service) to (service upower-service-type).
* doc/guix.texi (Desktop Services): Update the upower service documentation.

doc/guix.texi

@@ -34,6 +34,7 @@ Copyright @copyright{} 2016, 2017 Nils Gillmann@*
 Copyright @copyright{} 2016, 2017, 2018 Jan Nieuwenhuizen@*
 Copyright @copyright{} 2016 Julien Lepiller@*
 Copyright @copyright{} 2016 Alex ter Weele@*
+Copyright @copyright{} 2016, 2017, 2018, 2019 Christopher Baines@*
 Copyright @copyright{} 2017, 2018 Clément Lassieur@*
 Copyright @copyright{} 2017, 2018 Mathieu Othacehe@*
 Copyright @copyright{} 2017 Federico Beffa@*
@@ -14291,24 +14292,79 @@ capabilities to ordinary users.  For example, an ordinary user can be granted
 the capability to suspend the system if the user is logged in locally.
 @end deffn
-@deffn {Scheme Procedure} upower-service [#:upower @var{upower}] @
-                         [#:watts-up-pro? #f] @
-                         [#:poll-batteries? #t] @
-                         [#:ignore-lid? #f] @
-                         [#:use-percentage-for-policy? #f] @
-                         [#:percentage-low 10] @
-                         [#:percentage-critical 3] @
-                         [#:percentage-action 2] @
-                         [#:time-low 1200] @
-                         [#:time-critical 300] @
-                         [#:time-action 120] @
-                         [#:critical-power-action 'hybrid-sleep]
-Return a service that runs @uref{http://upower.freedesktop.org/,
-@command{upowerd}}, a system-wide monitor for power consumption and battery
-levels, with the given configuration settings.  It implements the
-@code{org.freedesktop.UPower} D-Bus interface, and is notably used by
-GNOME.
-@end deffn
+@defvr {Scheme Variable} upower-service-type
+Service that runs @uref{http://upower.freedesktop.org/, @command{upowerd}}, a
+system-wide monitor for power consumption and battery levels, with the given
+configuration settings.
+
+It implements the @code{org.freedesktop.UPower} D-Bus interface, and is
+notably used by GNOME.
+@end defvr
+
+@deftp {Data Type} upower-configuration
+Data type representation the configuration for UPower.
+
+@table @asis
+
+@item @code{upower} (default: @var{upower})
+Package to use for @code{upower}.
+
+@item @code{watts-up-pro?} (default: @code{#f})
+Enable the Watts Up Pro device.
+
+@item @code{poll-batteries?} (default: @code{#t})
+Enable polling the kernel for battery level changes.
+
+@item @code{ignore-lid?} (default: @code{#f})
+Ignore the lid state, this can be useful if it's incorrect on a device.
+
+@item @code{use-percentage-for-policy?} (default: @code{#f})
+Whether battery percentage based policy should be used.  The default is to use
+the time left, change to @code{#t} to use the percentage.
+
+@item @code{percentage-low} (default: @code{10})
+When @code{use-percentage-for-policy?} is @code{#t}, this sets the percentage
+at which the battery is considered low.
+
+@item @code{percentage-critical} (default: @code{3})
+When @code{use-percentage-for-policy?} is @code{#t}, this sets the percentage
+at which the battery is considered critical.
+
+@item @code{percentage-action} (default: @code{2})
+When @code{use-percentage-for-policy?} is @code{#t}, this sets the percentage
+at which action will be taken.
+
+@item @code{time-low} (default: @code{1200})
+When @code{use-time-for-policy?} is @code{#f}, this sets the time remaining in
+seconds at which the battery is considered low.
+
+@item @code{time-critical} (default: @code{300})
+When @code{use-time-for-policy?} is @code{#f}, this sets the time remaining in
+seconds at which the battery is considered critical.
+
+@item @code{time-action} (default: @code{120})
+When @code{use-time-for-policy?} is @code{#f}, this sets the time remaining in
+seconds at which action will be taken.
+
+@item @code{critical-power-action} (default: @code{'hybrid-sleep})
+The action taken when @code{percentage-action} or @code{time-action} is
+reached (depending on the configuration of @code{use-percentage-for-policy?}).
+
+Possible values are:
+
+@itemize @bullet
+@item
+@code{'power-off}
+
+@item
+@code{'hibernate}
+
+@item
+@code{'hybrid-sleep}.
+@end itemize
+
+@end table
+@end deftp
 @deffn {Scheme Procedure} udisks-service [#:udisks @var{udisks}]
 Return a service for @uref{http://udisks.freedesktop.org/docs/latest/,

gnu/services/desktop.scm

@@ -273,6 +273,11 @@ (define (upower-shepherd-service config)
 (define upower-service-type
   (let ((upower-package (compose list upower-configuration-upower)))
     (service-type (name 'upower)
+                  (description
+                   "Run @command{upowerd}}, a system-wide monitor for power
+consumption and battery levels, with the given configuration settings.  It
+implements the @code{org.freedesktop.UPower} D-Bus interface, and is notably
+used by GNOME.")
                   (extensions
                    (list (service-extension dbus-root-service-type
                                             upower-dbus-service)
@@ -285,7 +290,8 @@ (define upower-service-type
 
                          ;; Make the 'upower' command visible.
                          (service-extension profile-service-type
-                                            upower-package))))))
+                                            upower-package)))
+                  (default-value (upower-configuration)))))
 
 (define* (upower-service #:key (upower upower)
                          (watts-up-pro? #f)
@@ -1029,7 +1035,7 @@ (define %desktop-services
          (service wpa-supplicant-service-type)    ;needed by NetworkManager
          (service avahi-service-type)
          (udisks-service)
-         (upower-service)
+         (service upower-service-type)
          (accountsservice-service)
          (service cups-pk-helper-service-type)
          (colord-service)