tool: change the hwdb generator to the libwacom-update-db tool

Previously, the tool generated the hwdb and the rest was left to the user,
requiring more hand-holding in bug reports and more extensive documentation.

Change this to be a one-stop tool that takes care of all steps required by a
user, so a user can just run this tool with /etc/libwacom as argument and the
hwdb will be updated. Notably: the default invocation with /etc/libwacom an
*auxilary* hwdb based on the user's files rather than writing
out the whole one, overwriting the system one.

This is the 99%-case version of the tool, custom prefixes etc. will not be
handled as well as they can be but that's a niche case anyway and not worth
the effort. The vast majority of users will put the new file in to
/etc/libwacom and have the system installation in /usr/share/libwacom.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

4 files changed, 136 insertions, 57 deletions

diff --git a/README.md b/README.md
index 6d14407..7acb6f4 100644
--- a/README.md
+++ b/README.md
@@ -33,46 +33,52 @@ the tablet is not in that list.
 
 You must update udev after installing the file, see below.
 
-## To add support for a tablet to an older libwacom
+## To add support for a tablet to an installed libwacom
 
 If the system-provided libwacom does not include a `.tablet` file, it is
 possible to "backport" that `.tablet` file to the system-provided libwacom.
-Simply copy the `.tablet` file from the upstream git tree into the local
-directory `/etc/libwacom/`. Create that directory if necessary.
 
-For versions of libwacom older than 1.9, the file should be copied to
-`/usr/share/libwacom`. It may be overwritten on updates.
-
-You must update udev after installing the file, see below.
-
-## Updating udev's hwdb
-
-The new device must be added to the udev hwdb to ensure all required udev
-properties are set. Without a hwdb entry, the device may not be detected as
-tablet and may not work correctly.
+### libwacom 1.10 and newer
 
-### When building from source
+Copy the `.tablet` file into `/etc/libwacom` and run the
+`libwacom-update-db` tool:
 
-Generate an updated hwdb with `tools/generate-hwdb.py` after adding the
-tablet description to the `data/` directory. This is done automatically during
-the build, look for the `65-libwacom.hwdb` file in the build tree.
-This file is installed as part of `ninja install` or `make install`. Run the following
-command to activate the new hwdb set:
 ```
-$ sudo systemd-hwdb update
+$ cp my-tablet-file-from-upstream.tablet /etc/libwacom/
+$ libwacom-update-db /etc/libwacom
 ```
-Now disconnect and reconnect the device and it should be detected by libwacom.
 
-### When adding files to an installed version of libwacom
+The tool will take care of updating udev, the hwdb, etc.
+
+### libwacom 1.9 and earlier
 
-After installing the `.tablet` file in `/etc/libwacom/`, run
-the [`generate-hwdb.py`](https://github.com/linuxwacom/libwacom/blob/master/tools/generate-hwdb.py) tool:
-This tool can be run from the source tree.
+For versions of libwacom <= 1.9, the file must be copied to
+`/usr/share/libwacom`. It may be overwritten on updates.
+
+You must update udev after installing the file. The simplest (and broadest)
+way to do this is outlined below:
 
 ```
-$ generate-hwdb.py /etc/libwacom > 66-libwacom-local.hwdb
-$ sudo cp 66-libwacom-local.hwdb /etc/udev/hwdb.d/
-$ sudo systemd-hwdb update
+# create the hwdb file
+$ cat <EOF > /etc/udev/hwdb.d/66-libwacom.hwdb
+# WARNING: change "Your Device Name" to the actual name of your device
+libwacom:name:Your Device Name*:input:*
+ ID_INPUT=1
+ ID_INPUT_TABLET=1
+ ID_INPUT_JOYSTICK=0
+
+libwacom:name:Your Device Name Pad:input:*
+ ID_INPUT_TABLET_PAD=1
+
+# Use this if the device is an external tablet
+libwacom:name:Your Device Name Finger:input:*
+ ID_INPUT_TOUCHPAD=1
+
+# Use this if the device is a screen tablet
+libwacom:name:Your Device Name Finger:input:*
+ ID_INPUT_TOUCHSCREEN=1
+
+EOF
+$ systemd-hwdb --update
 ```
-
 Now disconnect and reconnect the device and it should be detected by libwacom.
diff --git a/meson.build b/meson.build
index 5450375..7e5ab82 100644
--- a/meson.build
+++ b/meson.build
@@ -154,11 +154,13 @@ executable('libwacom-list-local-devices',
 
 tools_cflags = ['-DDATABASEPATH="@0@"'.format(dir_src_data)]
 
-hwdb_generator = find_program('tools/generate-hwdb.py')
+updatedb = configure_file(input: 'tools/libwacom-update-db.py',
+			  output: '@BASENAME@',
+			  copy: true,
+			  install: true,
+			  install_dir: dir_bin)
 custom_target('hwdb',
-	      command: [python, hwdb_generator,
-		        '--include-wireless-accessory-kit',
-			dir_src_data],
+	      command: [python, updatedb, '--buildsystem-mode', dir_src_data],
 	      capture: true,
 	      output: '65-libwacom.hwdb',
 	      install: true,
diff --git a/tools/Makefile.am b/tools/Makefile.am
index d08ec97..b7d9fef 100644
--- a/tools/Makefile.am
+++ b/tools/Makefile.am
@@ -31,13 +31,15 @@ hwdb = 65-libwacom.hwdb
 udev_hwdbdir=$(UDEV_DIR)/hwdb.d
 dist_udev_hwdb_DATA = $(hwdb)
 
-$(hwdb): $(srcdir)/generate-hwdb.py
-	$(PYTHON) $(srcdir)/generate-hwdb.py --include-wireless-accessory-kit $(abs_top_srcdir)/data > $@
+$(hwdb): libwacom-update-db
+	$(PYTHON) $(builddir)/libwacom-update-db --buildsystem-mode $(abs_top_srcdir)/data > $@
 
-bin_SCRIPTS = libwacom-show-stylus
+bin_SCRIPTS = libwacom-show-stylus libwacom-update-db
 libwacom-show-stylus: show-stylus.py
 	sed -e 's|@DATADIR@|$(datadir)/libwacom|' -e 's|@ETCDIR@|$(sysconfdir)/libwacom|' $< > $@
 
+libwacom-update-db: libwacom-update-db.py
+	cp $< $@
 
 CLEANFILES = $(hwdb) $(bin_SCRIPTS)
-EXTRA_DIST = $(rules) $(hwdb) show-stylus.py generate-hwdb.py
+EXTRA_DIST = $(rules) $(hwdb) show-stylus.py libwacom-update-db.py
diff --git a/tools/generate-hwdb.py b/tools/libwacom-update-db.py
index 94488db..1531d1b 100755
--- a/tools/generate-hwdb.py
+++ b/tools/libwacom-update-db.py
@@ -23,6 +23,8 @@
 
 import argparse
 import configparser
+import sys
+import subprocess
 from pathlib import Path
 
 
@@ -84,20 +86,21 @@ class HWDBFile:
 
         return "\n".join(lines)
 
-    def print(self):
-        print("# hwdb entries for libwacom supported devices")
-        print("# This file is generated by libwacom, do not edit")
-        print("#")
-        print(
-            "# The lookup key is a contract between the udev rules and the hwdb entries."
+    def print(self, file=sys.stdout):
+        header = (
+            "# hwdb entries for libwacom supported devices",
+            "# This file is generated by libwacom, do not edit",
+            "#",
+            "# The lookup key is a contract between the udev rules and the hwdb entries.",
+            "# It is not considered public API and may change.",
+            "",
         )
-        print("# It is not considered public API and may change.")
-        print("")
+        print("\n".join(header), file=file)
 
         for t in self.tablets:
             entry = self._tablet_entry(t)
             if entry:
-                print(entry)
+                print(entry, file=file)
 
 
 class TabletDatabase:
@@ -142,34 +145,100 @@ class TabletDatabase:
                 yield t
 
 
+# Guess the udev directory based on path. For the case of /usr/share, the
+# udev directory is probably in /usr/lib so let's fallback to that.
+def find_udev_base_dir(path):
+    for parent in path.parents:
+        d = Path(parent / "udev" / "rules.d")
+        if d.exists():
+            return d.parent
+
+    # /usr/share but also any custom prefixes
+    for parent in path.parents:
+        d = Path(parent / "lib" / "udev" / "rules.d")
+        if d.exists():
+            return d.parent
+
+    raise FileNotFoundError(path)
+
+
+# udev's behaviour is that where a file X exists in two locations,
+# only the highest-precedence one is read. Our files in /etc are
+# supposed to be complimentary to the system ones so we have to
+# change the filename accordingly. We do so based on the prefix.
+def guess_hwdb_filename(basedir):
+    hwdbdir = Path(basedir) / "hwdb.d"
+    if not hwdbdir.exists():
+        raise FileNotFoundError(hwdbdir)
+
+    number = 66 if str(hwdbdir).startswith("/etc/") else 66
+    fname = hwdbdir / f"{number}-libwacom.hwdb"
+    return fname
+
+
 if __name__ == "__main__":
-    parser = argparse.ArgumentParser(description="hwdb generation tool")
+    parser = argparse.ArgumentParser(
+        description="Update the system according to the current set of tablet data files"
+    )
     parser.add_argument(
-        "paths", nargs="+", type=str, help="Directories to load .tablet files from"
+        "path", nargs="?", type=Path, default='/etc/libwacom',
+        help="Directory to load .tablet files from"
     )
+    # buildsystem-mode is what we use from meson/autotools, it changes the
+    # the behavior to just generate the file
     parser.add_argument(
-        "--include-wireless-accessory-kit",
+        "--buildsystem-mode",
         action="store_true",
         default=False,
-        help="Include an extra entry for the Wacom Wireless Accessory Kit",
+        help="be used by the build system only",
+    )
+    parser.add_argument(
+        "--skip-systemd-hwdb-update",
+        action="store_true",
+        default=False,
+        help="Do not run systemd-hwdb --update (Note: updates to tablet files will not be reflected in udev)",
+    )
+    parser.add_argument(
+        "--udev-base-dir",
+        type=Path,
+        default=None,
+        help="The udev base directory (default: guessed based on the path)",
     )
     ns = parser.parse_args()
 
-    tablets = []
-
-    for path in ns.paths:
-        tablets.extend(TabletDatabase(path).tablets)
+    db = TabletDatabase(ns.path)
 
     hwdb = HWDBFile()
     # Bamboo and Intuos devices connected to the system via Wacom's
     # Wireless Accessory Kit appear to udev as having the PID of the
     # dongle rather than the actual tablet. Make sure we properly tag
     # such devices.
-    if ns.include_wireless_accessory_kit:
+    #
+    # We only really care about this in the official hwdb files
+    if ns.buildsystem_mode:
         wwak = Tablet("Wacom Wireless Accessory Kit", "usb", "056A", "0084")
         wwak.has_pad = True
         wwak.has_touch = True
         hwdb.tablets.append(wwak)
 
-    hwdb.tablets.extend(tablets)
-    hwdb.print()
+    hwdb.tablets.extend(db.tablets)
+    if ns.buildsystem_mode:
+        hwdb.print()
+    else:
+        try:
+            udevdir = ns.udev_base_dir or find_udev_base_dir(ns.path)
+            hwdbfile = guess_hwdb_filename(udevdir)
+            with open(hwdbfile, "w") as fd:
+                hwdb.print(fd)
+            print(f"New hwdb file: {hwdbfile}")
+
+            if not ns.skip_systemd_hwdb_update:
+                subprocess.run(["systemd-hwdb", "update"],
+                        capture_output=True, check=True, text=True)
+            print("Finished, please unplug and replug your device")
+        except PermissionError as e:
+            print(f"{e}, please run me as root")
+        except FileNotFoundError as e:
+            print(f"Unable to find udev base directory: {e}")
+        except subprocess.CalledProcessError as e:
+            print(f"hwdb update failed: {e.stderr}")