From bc5a7eb4955465a8d77c378fb26e43714e219088 Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Thu, 7 Oct 2021 10:20:38 +0200
Subject: [PATCH] rom_filter: support default input values

Fixes #4286
---
 repos/os/recipes/pkg/test-rom_filter/runtime  | 20 ++++++++++++++-----
 repos/os/src/server/rom_filter/README         |  3 +++
 .../server/rom_filter/input_rom_registry.h    |  3 +++
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/repos/os/recipes/pkg/test-rom_filter/runtime b/repos/os/recipes/pkg/test-rom_filter/runtime
index 31618cd2d5..ace93b41c8 100644
--- a/repos/os/recipes/pkg/test-rom_filter/runtime
+++ b/repos/os/recipes/pkg/test-rom_filter/runtime
@@ -6,13 +6,13 @@
 		<timeout meaning="failed" sec="20" />
 		<log meaning="succeeded">
 			[init -> rom_logger] ROM 'generated':
-			[init -> rom_logger]   &lt;config>&lt;!-- ... fallback ... -->&lt;/config>*
+			[init -> rom_logger]   &lt;config color="transparent">&lt;!-- ... fallback ... -->&lt;/config>*
 			[init -> rom_logger] ROM 'generated':
-			[init -> rom_logger]   &lt;config>&lt;!-- ... fallback ... -->&lt;/config>*
+			[init -> rom_logger]   &lt;config color="transparent">&lt;!-- ... fallback ... -->&lt;/config>*
 			[init -> rom_logger] ROM 'generated':
-			[init -> rom_logger]   &lt;config>&lt;!-- xray enabled -->&lt;/config>*
+			[init -> rom_logger]   &lt;config color="yellow">&lt;!-- xray enabled -->&lt;/config>*
 			[init -> rom_logger] ROM 'generated':
-			[init -> rom_logger]   &lt;config message="system locked">&lt;!-- ... fallback ... -->&lt;/config>*
+			[init -> rom_logger]   &lt;config message="system locked" color="transparent">&lt;!-- ... fallback ... -->&lt;/config>*
 			[init -> dynamic_rom] xray: change (finished)
 		</log>
 		<log meaning="failed">Error: </log>
@@ -54,7 +54,9 @@
 					</inline>
 					<sleep milliseconds="1000" />
 					<inline description="enable X-ray mode">
-						<xray enabled="yes"/>
+						<xray enabled="yes">
+							<style color="yellow"/>
+						</xray>
 					</inline>
 					<sleep milliseconds="1000" />
 					<inline description="leave X-ray mode undefined">
@@ -80,6 +82,13 @@
 					<attribute name="enabled" />
 				</input>
 
+				<!-- test fallback to default value -->
+				<input name="color" rom="xray" node="xray" default="transparent">
+					<node type="style">
+						<attribute name="color" />
+					</node>
+				</input>
+
 				<input name="diagnostic_message" rom="xray" node="xray">
 					<node type="details">
 						<node type="message" attribute="reason" value="no access">
@@ -90,6 +99,7 @@
 
 				<output node="config">
 					<attribute name="message" input="diagnostic_message"/>
+					<attribute name="color"   input="color"/>
 					<if>
 						<has_value input="xray_enabled" value="yes" />
 						<then>
diff --git a/repos/os/src/server/rom_filter/README b/repos/os/src/server/rom_filter/README
index 6e142d28f2..b94ce5ad35 100644
--- a/repos/os/src/server/rom_filter/README
+++ b/repos/os/src/server/rom_filter/README
@@ -17,6 +17,9 @@ attribute. The 'rom' attribute specifies the ROM module to take the input
 from. If not specified, the 'name' is used as the ROM name. The type of the
 top-level XML node can be specified via the 'node' attribute. If not present,
 the top-level XML node is expected to correspond to the 'name' attribute.
+The optional 'default' attribute defines the input value used whenever the
+ROM module lacks the structure or attribute expected by the '<input>'.
+
 The '<input>' node may contain a hierarchy of '<node type="type">' nodes that
 denote a path within the XML input. If specified, the optional attributes
 'attribute' and 'value' constrain the selection of the input depending of the
diff --git a/repos/os/src/server/rom_filter/input_rom_registry.h b/repos/os/src/server/rom_filter/input_rom_registry.h
index 4e5f8ce8dd..1f0f6ee1be 100644
--- a/repos/os/src/server/rom_filter/input_rom_registry.h
+++ b/repos/os/src/server/rom_filter/input_rom_registry.h
@@ -233,6 +233,9 @@ class Rom_filter::Input_rom_registry
 
 					} catch (...) { }
 
+					if (input_node.has_attribute("default"))
+						return input_node.attribute_value("default", Input_value(""));
+
 					throw Nonexistent_input_value();
 				}