From d3d31eadcb4c210aea86698438af4371b9c4febc Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Sat, 19 Mar 2022 14:05:24 +0100
Subject: dev_add: add devices by name regex rather than path

Also, watch for new devices using udevadm monitor.
---
 README  |   5 +--
 dev_add | 109 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----------
 2 files changed, 93 insertions(+), 21 deletions(-)

diff --git a/README b/README
index 8f6361f..e7fedf4 100644
--- a/README
+++ b/README
@@ -57,5 +57,6 @@ The commands are:
 dev_add
 -------
 A helper tool that accepts the name (or full path) of the control FIFO and a
-real device node. It adds that device through the FIFO, then sleeps until
-interrupted. On exit it removes the device it added.
+regex pattern. It adds all input devices whose name matches the pattern
+(monitoring newly newly added devices using udevadm). On exit it clears all
+bound devices (unless the --no-clear option is used).
diff --git a/dev_add b/dev_add
index ba7ab6b..1e0b092 100755
--- a/dev_add
+++ b/dev_add
@@ -1,37 +1,108 @@
 #!/usr/bin/python3
 
+import argparse
 import contextlib
+import glob
+import logging
 import os
+import re
 import selectors
+import subprocess
 import sys
 import time
 
-control_path = os.path.expanduser(sys.argv[1])
+def dev_match(evpath, pattern, logger):
+    try:
+        with open(evpath + '/device/name', 'r') as f:
+            name = f.read()
+        with open(evpath + '/device/phys', 'r') as f:
+            phys = f.read()
+
+        if not 'uinput' in phys and re.search(pattern, name):
+            logger.debug('%s matched the pattern', evpath)
+            return True
+    except IOError:
+        pass
+
+    logger.debug('%s did not match the pattern', evpath)
+    return False
+
+def dev_add(control, syspath, logger):
+    devpath = '/dev/input/' + os.path.basename(syspath)
+    control.write('add ' + devpath + '\n')
+    control.flush()
+
+    logger.info('Added device: %s', devpath)
+
+parser = argparse.ArgumentParser()
+
+parser.add_argument('-v', '--verbose',  action = 'count', default = 0)
+parser.add_argument('-q', '--quiet',    action = 'count', default = 0)
+parser.add_argument('-n', '--no-clear', action = 'store_true')
+parser.add_argument('control')
+parser.add_argument('device')
+
+args = parser.parse_args(sys.argv[1:])
+
+# setup logging
+# default to 20 (INFO), every -q goes a level up, every -v a level down
+log_level  = max(10 * (2 + args.quiet - args.verbose), 0)
+log_format = '%(asctime)s:%(name)s:%(levelname)s: %(message)s'
+logging.basicConfig(format = log_format, datefmt = '%F %T', level = log_level)
+logger = logging.getLogger(os.path.basename(sys.argv[0]))
+
+control_path = os.path.expanduser(args.control)
 if not control_path or control_path[0] != '/':
     control_path = os.path.join(os.path.expanduser('~/.cache/inputfwd'),
-                                sys.argv[1])
+                                args.control)
 
 if not os.path.exists(control_path):
-    sys.stderr.write('Control path "%s"->"%s" does not exist.\n' % (sys.argv[1], control_path))
-
-devpath = sys.argv[2]
-if not os.path.exists(devpath):
-    sys.stderr.write('Device path "%s" does not exist.\n' % devpath)
+    sys.stderr.write('Control path "%s"->"%s" does not exist.\n' % (args.control, control_path))
 
 with contextlib.ExitStack() as stack:
     sel = stack.enter_context(selectors.DefaultSelector())
 
-    f = stack.enter_context(open(control_path, 'w'))
+    # open the control FIFO
+    control = stack.enter_context(open(control_path, 'w'))
+
+    # do the initial scan
+    for dev in glob.glob('/sys/class/input/event*'):
+        if dev_match(dev, args.device, logger):
+            dev_add(control, dev, logger)
+
+    # monitor new input devices
+    udevadm = subprocess.Popen(['udevadm', 'monitor', '--subsystem-match=input', '--udev'],
+                               stdout = subprocess.PIPE, bufsize = 0)
+    stack.callback(lambda p: p.terminate(), udevadm)
+
+    sel.register(control,        selectors.EVENT_READ)
+    sel.register(udevadm.stdout, selectors.EVENT_READ)
+
+    while True:
+        try:
+            events = sel.select()
+        except KeyboardInterrupt:
+            logger.info('Interrupted')
+            if not args.no_clear:
+                logger.info('Clearing devices')
+                control.write('clear\n')
+                control.flush()
+            break
+
+        for key, mask in events:
+            # read event on the control pipe means remote hangup
+            if key.fileobj == control:
+                logger.error('Remote end hung up, terminating')
+                break
+
+            # udevadm event
+            line = key.fileobj.read(4096).decode('ascii').strip()
+            logger.debug('udevadm line: %s', line)
+
+            m = re.search(r'add\s+(\S+/event\d+)', line)
+            if m is not None:
+                syspath = '/sys' + m.group(1)
+                if dev_match(syspath, args.device, logger):
+                    dev_add(control, syspath, logger)
 
-    f.write('add ' + devpath + '\n')
-    f.flush()
 
-    # sleep until interrupted
-    sel.register(f, selectors.EVENT_READ)
-    try:
-        sel.select()
-        sys.stderr.write('Remote end hung up.\n')
-    except KeyboardInterrupt:
-        sys.stderr.write('Interrupted, removing device and existing\n')
-        f.write('remove ' + devpath + '\n')
-        f.flush()
-- 
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