input-device: Check for sections matching key udev properties

This patch adds additional checks for input-device sections in the config
file. It checks for ID_PATH, ID_SERIAL, LIBINPUT_DEVICE_GROUP then falls
back to the device name and finally the global input-device section. In
addition, DEVPATH is printed to log when WF_PRINT_UDEV_DEVPATH is set and
'-d' is passed to wayfire, for matching the correct device in i.e.
'udevadm info --tree'. The sections that wayfire checks for are also
logged with '-d'. This makes it so users can match devices, especially
identical devices lacking many of the usual differentiating properties.

Fixes #2504.

meson.build

@@ -34,6 +34,7 @@ pixman         = dependency('pixman-1')
 xkbcommon      = dependency('xkbcommon')
 libdl          = meson.get_compiler('cpp').find_library('dl')
 json           = dependency('nlohmann_json', version: '>= 3.11.2')
+udev           = dependency('libudev')
 
 # We're not to use system wlroots: So we'll use the subproject
 if get_option('use_system_wlroots').disabled()

src/core/plugin.cpp

@@ -5,6 +5,7 @@
 #include "wayfire/signal-definitions.hpp"
 #include <wayfire/util/log.hpp>
 #include <wayfire/config-backend.hpp>
+#include <libudev.h>
 
 void wf::plugin_interface_t::fini()
 {}
@@ -27,18 +28,76 @@ std::shared_ptr<config::section_t> wf::config_backend_t::get_output_section(
     return config.get_section(name);
 }
 
+static struct udev_property_and_desc
+{
+    char const *property_name;
+    char const *description;
+} properties_and_descs[] =
+{
+    {"ID_PATH", "stable physical connection path"},
+    {"ID_SERIAL", "stable vendor+pn+sn info"},
+    {"LIBINPUT_DEVICE_GROUP", "stable libinput info"},
+    // sometimes it contains info "by path", sometimes "by id"
+    {"DEVPATH", "unstable devpath"},
+    // used for debugging, to find DEVPATH and match the right
+    // device in `udevadm info --tree`
+};
+
 std::shared_ptr<config::section_t> wf::config_backend_t::get_input_device_section(
     wlr_input_device *device)
 {
+    auto& config = wf::get_core().config;
+    std::shared_ptr<wf::config::section_t> section;
+    auto print_devpath = getenv("WF_PRINT_UDEV_DEVPATH");
+
+    if (wlr_input_device_is_libinput(device))
+    {
+        auto libinput_dev = wlr_libinput_get_device_handle(device);
+        if (libinput_dev)
+        {
+            udev_device *udev_dev = libinput_device_get_udev_device(libinput_dev);
+            if (udev_dev)
+            {
+                for (struct udev_property_and_desc const & pd : properties_and_descs)
+                {
+                    if (!print_devpath && !strncmp(pd.property_name, "DEVPATH", strlen("DEVPATH")))
+                    {
+                        continue;
+                    }
+
+                    const char *value = udev_device_get_property_value(udev_dev, pd.property_name);
+                    if (value == nullptr)
+                    {
+                        continue;
+                    }
+
+                    std::string name = std::string("input-device:") + nonull(value);
+                    LOGD("Checking for config section [", name, "] ",
+                        pd.property_name, " (", pd.description, ")");
+                    section = config.get_section(name);
+                    if (section)
+                    {
+                        LOGD("Using config section [", name, "] for ", nonull(device->name));
+                        return section;
+                    }
+                }
+            }
+        }
+    }
+
     std::string name = nonull(device->name);
     name = "input-device:" + name;
-    auto& config = wf::get_core().config;
-    if (!config.get_section(name))
+    LOGD("Checking for config section [", name, "]");
+    section = config.get_section(name);
+    if (section)
     {
-        config.merge_section(
-            config.get_section("input-device")->clone_with_name(name));
+        LOGD("Using config section [", name, "]");
+        return section;
     }
 
+    config.merge_section(
+        config.get_section("input-device")->clone_with_name(name));
+
     return config.get_section(name);
 }
 

src/meson.build

@@ -64,7 +64,8 @@ wayfire_sources = ['geometry.cpp',
 
 wayfire_dependencies = [wayland_server, wlroots, xkbcommon, libinput,
                        pixman, drm, egl, glesv2, glm, wf_protos, libdl,
-                       wfconfig, libinotify, backtrace, wfutils, xcb, wftouch, json]
+                       wfconfig, libinotify, backtrace, wfutils, xcb,
+                       wftouch, json, udev]
 
 if conf_data.get('BUILD_WITH_IMAGEIO')
     wayfire_dependencies += [jpeg, png]