fan_generic: Support setting a TEMPLATE on SET_FAN_SPEED commands

Signed-off-by: Kevin O'Connor <[email protected]>

docs/G-Codes.md

@@ -476,6 +476,20 @@ enabled.
 `SET_FAN_SPEED FAN=config_name SPEED=<speed>` This command sets the
 speed of a fan. "speed" must be between 0.0 and 1.0.
 
+`SET_FAN_SPEED PIN=config_name TEMPLATE=<template_name>
+[<param_x>=<literal>]`: If `TEMPLATE` is specified then it assigns a
+[display_template](Config_Reference.md#display_template) to the given
+fan. For example, if one defined a `[display_template
+my_fan_template]` config section then one could assign
+`TEMPLATE=my_fan_template` here. The display_template should produce a
+string containing a floating point number with the desired value. The
+template will be continuously evaluated and the fan will be
+automatically set to the resulting speed. One may set display_template
+parameters to use during template evaluation (parameters will be
+parsed as Python literals). If TEMPLATE is an empty string then this
+command will clear any previous template assigned to the pin (one can
+then use `SET_FAN_SPEED` commands to manage the values directly).
+
 ### [filament_switch_sensor]
 
 The following command is available when a

klippy/extras/fan_generic.py

@@ -1,9 +1,9 @@
 # Support fans that are controlled by gcode
 #
-# Copyright (C) 2016-2020  Kevin O'Connor <[email protected]>
+# Copyright (C) 2016-2024  Kevin O'Connor <[email protected]>
 #
 # This file may be distributed under the terms of the GNU GPLv3 license.
-from . import fan
+from . import fan, output_pin
 
 class PrinterFanGeneric:
     cmd_SET_FAN_SPEED_help = "Sets the speed of a fan"
@@ -12,6 +12,9 @@ def __init__(self, config):
         self.fan = fan.Fan(config, default_shutdown_speed=0.)
         self.fan_name = config.get_name().split()[-1]
 
+        # Template handling
+        self.template_eval = output_pin.lookup_template_eval(config)
+
         gcode = self.printer.lookup_object("gcode")
         gcode.register_mux_command("SET_FAN_SPEED", "FAN",
                                    self.fan_name,
@@ -20,8 +23,21 @@ def __init__(self, config):
 
     def get_status(self, eventtime):
         return self.fan.get_status(eventtime)
+    def _template_update(self, text):
+        try:
+            value = float(text)
+        except ValueError as e:
+            logging.exception("fan_generic template render error")
+        self.fan.set_speed(value)
     def cmd_SET_FAN_SPEED(self, gcmd):
-        speed = gcmd.get_float('SPEED', 0.)
+        speed = gcmd.get_float('SPEED', None, 0.)
+        template = gcmd.get('TEMPLATE', None)
+        if (speed is None) == (template is None):
+            raise gcmd.error("SET_FAN_SPEED must specify SPEED or TEMPLATE")
+        # Check for template setting
+        if template is not None:
+            self.template_eval.set_template(gcmd, self._template_update)
+            return
         self.fan.set_speed_from_command(speed)
 
 def load_config_prefix(config):