From 0da45161507ce0f944834483972234ab41c3ea2d Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Tue, 16 Apr 2024 16:26:12 +0200
Subject: [PATCH] edid-drm: Handle monitors in stand-by mode

---
 edid-drm | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/edid-drm b/edid-drm
index abe755d..5e1bb90 100755
--- a/edid-drm
+++ b/edid-drm
@@ -1,10 +1,24 @@
 #!/bin/sh
+# Scan all output of all video cards known to Linux Direct Rendering Manager
+# and identify connected displays.
+
 set -e
+exit_code=0
 for a in /sys/class/drm/card*-* ; do
-	if [ -f $a/edid -a "$(cat 2>/dev/null $a/enabled)" = enabled ] ; then
-		echo "### $(basename $a) ###"
-		echo
-		$(dirname $0)/edid <$a/edid
-		echo
+	if [ -f $a/edid ] ; then
+		# This is tricky: for disconnected outputs, the edid file exists,
+		# but it is empty. Monitors in stand-by mode have the "enabled"
+		# attribute set to "disabled", but the edid file is still valid.
+		# Since the file is purely virtual, we need to copy it first.
+		x=$(mktemp)
+		cp $a/edid $x
+		if [ -s $x ] ; then
+			echo "### $(basename $a) ###"
+			echo
+			edid <$x || exit_code=1
+			echo
+		fi
+		rm -f $x
 	fi
 done
+exit $exit_code
-- 
2.39.2