From 7dd2e1776eef60a8a5c739b5cad67d649946d393 Mon Sep 17 00:00:00 2001
From: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Date: Tue, 30 Apr 2019 01:32:59 -0300
Subject: [PATCH] sane-backends: rebind printers to usblp after scan

While scanning, sane unbinds usb device from usblp module. This
patch creates a saned wrapper that keep track of all usb devices
binded to usblp before saned is launched and rebind them back
if not still bound after saned exits.

This workaround is only effective if saned is launched by a super
daemon like xinetd as it needs to exit after scan job finish. If
not, printing will not be available while saned service is running.

Write access to /sys/bus/usb/drivers/usblp/bind is required. So,
normally it would require root access.

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
---
 utils/sane-backends/Makefile                  | 10 ++++----
 .../xinetd.d/sane-port}                       |  0
 utils/sane-backends/files/usr/sbin/saned      | 24 +++++++++++++++++++
 3 files changed, 30 insertions(+), 4 deletions(-)
 rename utils/sane-backends/files/{xinet.d_sane-port => etc/xinetd.d/sane-port} (100%)
 create mode 100755 utils/sane-backends/files/usr/sbin/saned

diff --git a/utils/sane-backends/Makefile b/utils/sane-backends/Makefile
index f4077c3a1..774428d7f 100644
--- a/utils/sane-backends/Makefile
+++ b/utils/sane-backends/Makefile
@@ -1,6 +1,6 @@
 #
 # Copyright (C) 2006-2016 OpenWrt.org
-# Copyright (C) 2017-2018 Luiz Angelo Daros de Luca <luizluca@gmail.com>
+# Copyright (C) 2017-2019 Luiz Angelo Daros de Luca <luizluca@gmail.com>
 #
 # This is free software, licensed under the GNU General Public License v2.
 # See /LICENSE for more information.
@@ -10,7 +10,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=sane-backends
 PKG_VERSION:=1.0.27
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=http://fossies.org/linux/misc \
     https://alioth.debian.org/frs/download.php/file/4146/
@@ -193,9 +193,11 @@ define Package/sane-daemon/install
 	$(INSTALL_DIR) $(1)/etc/sane.d
 	$(INSTALL_CONF) $(PKG_INSTALL_DIR)/etc/sane.d/saned.conf $(1)/etc/sane.d/
 	$(INSTALL_DIR) $(1)/usr/sbin
-	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/sbin/* $(1)/usr/sbin/
+	$(INSTALL_BIN) ./files/usr/sbin/saned $(1)/usr/sbin/saned
+	$(INSTALL_DIR) $(1)/usr/lib/sane/
+	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/sbin/saned $(1)/usr/lib/sane/saned
 	$(INSTALL_DIR) $(1)/etc/xinetd.d
-	$(CP) ./files/xinet.d_sane-port $(1)/etc/xinetd.d/sane-port
+	$(CP) ./files/etc/xinetd.d/sane-port $(1)/etc/xinetd.d/sane-port
 endef
 
 define Package/sane-daemon/conffiles
diff --git a/utils/sane-backends/files/xinet.d_sane-port b/utils/sane-backends/files/etc/xinetd.d/sane-port
similarity index 100%
rename from utils/sane-backends/files/xinet.d_sane-port
rename to utils/sane-backends/files/etc/xinetd.d/sane-port
diff --git a/utils/sane-backends/files/usr/sbin/saned b/utils/sane-backends/files/usr/sbin/saned
new file mode 100755
index 000000000..711492633
--- /dev/null
+++ b/utils/sane-backends/files/usr/sbin/saned
@@ -0,0 +1,24 @@
+#!/bin/sh
+
+usblp_driver="/sys/bus/usb/drivers/usblp"
+
+inuse=""
+if [ -e /sys/bus/usb/devices ]; then
+	for usbdev_driver in /sys/bus/usb/devices/*/driver; do
+		[ -e "$usbdev_driver" ] || continue
+		[ "$(readlink -f "$usbdev_driver")" = "$usblp_driver" ] || continue
+		usbdev="${usbdev_driver%/*}"
+		inuse="$inuse ${usbdev##*/}"
+	done
+fi
+
+/usr/lib/sane/saned "$@"
+err=$?
+
+for usbdev in $inuse; do
+	[ -e "/sys/bus/usb/devices/$usbdev/driver" ] && continue
+	logger -t saned "binding device $usbdev back to usblp..."
+	printf '%s' "$usbdev" > "$usblp_driver/bind"
+done
+
+exit $err