[slx-brightness] Add new module to control backlit displays

We do this raw by reading /dev/input/eventX to make sure no running
program (e.g. VMware Player) can grab the keyboard and prevent any other
running daemon (e.g. xfce-power-manager) from seeing the keystrokes.

Another advantage is that this will work everywhere (tty, lightdm, VM,
desktop session) since the daemon starts on system bootup.

7 files changed, 418 insertions, 0 deletions

diff --git a/core/modules/debug-report-bwlp/data/opt/openslx/bin/debug_report b/core/modules/debug-report-bwlp/data/opt/openslx/bin/debug_report
index 4f676f5c..f228e9c5 100755
--- a/core/modules/debug-report-bwlp/data/opt/openslx/bin/debug_report
+++ b/core/modules/debug-report-bwlp/data/opt/openslx/bin/debug_report
@@ -15,6 +15,7 @@ TOOLS=(
 	mount
 	dmesg
 	dmidecode
+	"slx-brightness -l"
 )
 
 URLS="
diff --git a/core/modules/slx-brightness/data/etc/systemd/system/multi-user.target.wants/slx-brightness.service b/core/modules/slx-brightness/data/etc/systemd/system/multi-user.target.wants/slx-brightness.service
new file mode 120000
index 00000000..6cbe2a91
--- /dev/null
+++ b/core/modules/slx-brightness/data/etc/systemd/system/multi-user.target.wants/slx-brightness.service
@@ -0,0 +1 @@
+../slx-brightness.service
\ No newline at end of file
diff --git a/core/modules/slx-brightness/data/etc/systemd/system/slx-brightness.service b/core/modules/slx-brightness/data/etc/systemd/system/slx-brightness.service
new file mode 100644
index 00000000..c75fdaf0
--- /dev/null
+++ b/core/modules/slx-brightness/data/etc/systemd/system/slx-brightness.service
@@ -0,0 +1,7 @@
+[Unit]
+Description=Handle display brightness keys
+
+[Service]
+Type=forking
+ExecStart=/opt/openslx/scripts/systemd-slx_brightness
+Restart=on-failure
diff --git a/core/modules/slx-brightness/data/opt/openslx/scripts/systemd-slx_brightness b/core/modules/slx-brightness/data/opt/openslx/scripts/systemd-slx_brightness
new file mode 100755
index 00000000..25925df8
--- /dev/null
+++ b/core/modules/slx-brightness/data/opt/openslx/scripts/systemd-slx_brightness
@@ -0,0 +1,78 @@
+#!/bin/bash
+
+if ! command -v slx-brightness &> /dev/null; then
+	echo "Error: Required tool slx-brightness not in path"
+	exit 1
+fi
+
+# How many steps we want from min to max
+declare -rg steps=15
+
+# Look for brightness config file
+#
+max_file="/sys/class/backlight/intel_backlight/max_brightness"
+cur_file="/sys/class/backlight/intel_backlight/brightness"
+
+if ! [ -e "$max_file" ] || ! [ -e "$cur_file" ]; then
+	for max_file in /sys/class/backlight/*/max_brightness; do
+		cur_file="${max_file%/*}/brightness"
+		[ -e "$max_file" ] && [ -e "$cur_file" ] && break
+	done
+fi
+
+if ! [ -e "$max_file" ] || ! [ -e "$cur_file" ]; then
+	echo "No brightness controls found, exiting"
+	exit 0
+fi
+
+# Calc sane limits
+#
+max=$( cat "$max_file" )
+if ! (( max > 0 )); then
+	echo "Max brightness is '$max', doing nothing"
+	exit 0
+fi
+
+min=$(( max / ( steps + 1 ) ))
+
+# Start our daemon
+#
+slx-brightness "$cur_file" "$min" "$max" "$steps" &
+pid=$!
+
+# Give it time to start
+sleep 3
+
+if ! kill -0 "$pid"; then
+	# slx-brightness exits if it doesn't find a known input device for brightness control
+	echo "slx-brightness didn't find a suitable device :-("
+	t="$( mktemp )"
+	if [ -n "$t" ]; then
+		slx-brightness -l &> "$t"
+		slxlog --delete --sync "screen-brightness" \
+			"Device seems to have controllable backlight, but cannot find suitable input device" "$t"
+	fi
+	exit 0
+fi
+
+# Disable handling of keys by xfce-power-manager
+#
+pmfile="/etc/xdg/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml"
+if ! [ -s "$pmfile" ]; then
+	mkdir -p "${pmfile%/*}"
+	cat > "$pmfile" <<-EOF
+		<?xml version="1.0" encoding="UTF-8"?>
+
+		<channel name="xfce4-power-manager" version="1.0" locked="*" unlocked="root">
+			<property name="xfce4-power-manager" type="empty">
+				<property name="handle-brightness-keys" type="bool" value="false"/>
+			</property>
+		</channel>
+EOF
+else
+	xmlstarlet ed -u '/channel/property/property[@name="handle-brightness-keys"]/@value' \
+			-v "false" "$pmfile" > "$pmfile.tmp" \
+		&& mv -f "$pmfile.tmp" "$pmfile"
+fi
+
+exit 0
diff --git a/core/modules/slx-brightness/module.build b/core/modules/slx-brightness/module.build
new file mode 100644
index 00000000..c6b478c4
--- /dev/null
+++ b/core/modules/slx-brightness/module.build
@@ -0,0 +1,8 @@
+#!/bin/bash
+
+build() {
+	local dest="${MODULE_BUILD_DIR}/opt/openslx/sbin"
+	mkdir -p "$dest" || perror "Cannot create $dest"
+	gcc -Wall -pedantic -Wextra -Werror -o "$dest/slx-brightness" "${MODULE_DIR}/src/main.c" \
+		|| perror "Cannot compile slx-brightness"
+}
diff --git a/core/modules/slx-brightness/module.conf b/core/modules/slx-brightness/module.conf
new file mode 100644
index 00000000..f4705015
--- /dev/null
+++ b/core/modules/slx-brightness/module.conf
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+REQUIRED_BINARIES="
+	slx-brightness
+"
diff --git a/core/modules/slx-brightness/src/main.c b/core/modules/slx-brightness/src/main.c
new file mode 100644
index 00000000..410154e0
--- /dev/null
+++ b/core/modules/slx-brightness/src/main.c
@@ -0,0 +1,318 @@
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <sys/epoll.h>
+#include <stdio.h>
+#include <linux/input.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+int open_events( int ep );
+
+bool handle_fd( int fd );
+
+void handle_message( struct input_event *ev );
+
+ssize_t file_get_contents( const char *filename, char *buffer, size_t len );
+
+ssize_t file_put_contents( const char *filename, const char *buffer, size_t len );
+
+int _min, _max, _step;
+const char *_brightness_file;
+bool _all;
+
+int main( int argc, char **argv )
+{
+	int steps, ep, num, valid;
+	struct epoll_event events[10];
+
+	// List all devices by name
+	if ( argc > 1 && strcmp( "-l", argv[1] ) == 0 ) {
+		open_events( -1 );
+		return 0;
+	}
+
+	// Listen to all devices
+	if ( argc > 1 && strcmp( "-a", argv[1] ) == 0 ) {
+		_all = true;
+		argc--;
+		argv++;
+	}
+
+	if ( argc < 5 ) {
+		fprintf( stderr, "%s <path> <min> <max> <num_steps>\n", argv[0] );
+		return 1;
+	}
+
+	// Sanity checks, calculate step size
+	_brightness_file = argv[1];
+	_min = atoi( argv[2] );
+	_max = atoi( argv[3] );
+	steps = atoi( argv[4] );
+	if ( _max <= _min || steps < 1 ) {
+		fprintf( stderr, "Error: min(%d) >= max(%d), or steps(%d) < 1\n", _min, _max, steps );
+		return 1;
+	}
+	_step = ( _max - _min ) / steps;
+	if ( _step < 1 ) {
+		_step = 1;
+	}
+
+	ep = epoll_create( 100 );
+	if ( ep == -1 ) {
+		perror( "Cannot epoll_create" );
+		return 1;
+	}
+
+	// Scan all input-event devices, open all that potentially have brightness keys
+	// As of now, we match only one so epoll is pointless, but I only checked two
+	// laptop models, so maybe there are different ways out there. Let's be prepared.
+	valid = open_events( ep );
+	if ( valid < 1 ) {
+		fprintf( stderr, "Nothing to wait for, exiting\n" );
+		return 0;
+	}
+
+	printf( "Waiting...\n" );
+	while ( ( num = epoll_wait( ep, events, 10, -1 ) ) > 0
+			|| ( num == -1 && errno == EINTR ) ) {
+		for ( int i = 0; i < num; ++i ) {
+			if ( !handle_fd( events[i].data.fd ) ) {
+				// Try to remove
+				if ( epoll_ctl( ep, EPOLL_CTL_DEL, events[i].data.fd, NULL ) == 0 ) {
+					valid--;
+					close( events[i].data.fd );
+				}
+			}
+		}
+	}
+	if ( num == -1 ) {
+		perror( "epoll error" );
+		return 1;
+	}
+	fprintf( stderr, "Unexpected loop exit\n" );
+	return 0;
+}
+
+/**
+ * Open all /dev/input/eventX, check the name against known ones with
+ * brightness controls.
+ * Pass ep == -1 to just print all the device names.
+ */
+int open_events( int ep )
+{
+	int opened = 0;
+	int fails = 0;
+	int h, len;
+	char fn[200];
+
+	for ( int id = 0 ;; ++id ) {
+		if ( snprintf( fn, sizeof(fn), "/dev/input/event%d", id ) == -1 ) {
+			perror( "snprintf broken" );
+			break;
+		}
+
+		// Open and see if success
+		h = open( fn, O_RDONLY );
+		if ( h == -1 ) {
+			if ( errno == ENOENT ) {
+				// Not found - potentially no more devices, but keep going for a bit, since for example
+				// unplugging a USB device would leave a gap in the numbering.
+				if ( ++fails < 10 )
+					continue;
+			} else {
+				perror( "Cannot open eventX" );
+			}
+			break;
+		}
+		// Success, inspect
+		if ( ep == -1 ) {
+			printf( "Opened %s: ", fn );
+		}
+		fails = 0;
+		len = ioctl( h, EVIOCGNAME( sizeof(fn) ), fn );
+		if ( len <= 0 ) {
+			perror( "Could not get device name" );
+			close( h );
+			continue;
+		}
+		if ( ep == -1 ) {
+			printf( "%.*s\n", len, fn );
+			close( h );
+			continue;
+		}
+
+		if ( !_all && strcmp( "Video Bus", fn ) != 0 ) {
+			printf( "Ignoring '%s'\n", fn );
+			close( h );
+			continue;
+		}
+
+		printf( "Listening on '%s'\n", fn );
+		// Make nonblocking, add to epoll set
+		fcntl( h, F_SETFL, O_NONBLOCK );
+		struct epoll_event ee = {
+			.events = EPOLLIN,
+			.data.fd = h,
+		};
+		if ( epoll_ctl( ep, EPOLL_CTL_ADD, h, &ee ) == -1 ) {
+			perror( "Cannot add eventX fd to epoll set" );
+			close( h );
+		} else {
+			opened++;
+		}
+	}
+
+	return opened;
+}
+
+/**
+ * Read events from fd.
+ */
+bool handle_fd( int fd )
+{
+	int num;
+	int done = 0;
+	struct input_event buf;
+
+	while ( ( num = read( fd, ( (char*)&buf ) + done, sizeof(buf) - done ) ) > 0
+			|| ( num == -1 && errno == EINTR ) ) {
+		if ( num + done == sizeof(buf) ) {
+			handle_message( &buf );
+			if ( done != 0 ) {
+				done = 0;
+				// Switch to nonblocking again
+				fcntl( fd, F_SETFL, O_NONBLOCK );
+			}
+		} else {
+			printf( "WARNING: PARTIAL READ\n" );
+			// Switch to blocking so we can finish the message
+			fcntl( fd, F_SETFL, 0 );
+			done += num;
+		}
+	}
+	if ( num == -1 && errno != EAGAIN ) {
+		perror( "Error reading event" );
+		return false;
+	}
+	return true;
+}
+
+/**
+ * Gets passed read events in input_event struct,
+ * check and handle brightness keys.
+ */
+void handle_message( struct input_event *ev )
+{
+	ssize_t len;
+	int val, newval;
+	char buf[100];
+
+	//printf( "Type: %d, Key %d, Value %d\n", (int)ev->type, (int)ev->code, (int)ev->value );
+	if ( ev->type != EV_KEY )
+		return;
+	if ( ev->value != 1 && ev->value != 2 )
+		return; // Down or Repeat only
+	if ( ev->code != KEY_BRIGHTNESSDOWN && ev->code != KEY_BRIGHTNESSUP )
+		return; // Match our keys
+
+	// Get current brightness
+	len = file_get_contents( _brightness_file, buf, sizeof(buf) );
+	if ( len <= 0 ) {
+		fprintf( stderr, "Cannot read brightness\n" );
+		return;
+	}
+
+	// Calculate new brightness
+	val = atoi( buf );
+	newval = val +  _step * ( ev->code == KEY_BRIGHTNESSUP ? 1 : -1 );
+	if ( newval < _min ) {
+		newval = _min;
+	} else if ( newval > _max ) {
+		newval = _max;
+	}
+	if ( val == newval )
+		return;
+
+	// Set new brightness
+	len = snprintf( buf, sizeof(buf), "%d", newval );
+	if ( len == -1 ) {
+		perror( "Brightness snprintf fail" );
+	} else if ( len == 0 ) {
+		fprintf( stderr, "Brightness snprintf returned zero\n" );
+	} else {
+		file_put_contents( _brightness_file, buf, (size_t)len );
+	}
+}
+
+/**
+ * Read file contents into buffer.
+ */
+ssize_t file_get_contents( const char *filename, char *buffer, size_t len )
+{
+	ssize_t ret;
+	size_t done = 0;
+	ssize_t bytes_read = -1;
+	int fd;
+
+	if ( len <= 1 ) {
+		if ( len == 1 ) {
+			buffer[0] = '\0';
+		}
+		return 0;
+	}
+	len--;
+
+	fd = open( filename, O_RDONLY );
+	if ( fd == -1 ) {
+		fprintf( stderr, "%s: ", filename );
+		perror( "Error opening file" );
+		return -1;
+	}
+
+	while ( done < len && ( bytes_read = read( fd, buffer + done, len - done ) ) > 0 ) {
+		done += bytes_read;
+	}
+	if ( bytes_read == -1 ) {
+		fprintf( stderr, "%s: ", filename );
+		perror( "Error reading file" );
+		ret = -1;
+	} else {
+		ret = (ssize_t)done;
+		buffer[done] = '\0';
+	}
+
+	close( fd );
+	return ret;
+}
+
+/**
+ * Write buffer contents to file.
+ */
+ssize_t file_put_contents( const char *filename, const char *buffer, size_t len )
+{
+	ssize_t ret;
+	size_t done = 0;
+	ssize_t bytes_written = -1;
+	int fd = open( filename, O_WRONLY | O_CREAT | O_TRUNC, 0644 );
+
+	if ( fd == -1 ) {
+		fprintf( stderr, "%s: ", filename );
+		perror( "Error opening file" );
+		return -1;
+	}
+
+	while ( done < len && ( bytes_written = write( fd, buffer + done, len - done ) ) > 0 ) {
+		done += bytes_written;
+	}
+	if ( bytes_written == -1 ) {
+		fprintf( stderr, "%s: ", filename );
+		perror( "Error writing file" );
+		ret = -1;
+	} else {
+		ret = (ssize_t)done;
+	}
+	close( fd );
+	return ret;
+}