From 1baf39daf718861e36af3ec166c76e4569411fd2 Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Sun, 24 Jul 2022 19:36:50 +0300
Subject: [PATCH] backends/drm: Improve device seat assignment handling

This fixes the drm backend adding hotplugged gpus that belong to other
seats and makes the udev helper depend on less stuff from the layer
above backends.
---
 src/backends/drm/drm_backend.cpp | 16 +++++++++++++---
 src/utils/udev.cpp               | 25 +++++++++++--------------
 src/utils/udev.h                 |  1 +
 3 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/src/backends/drm/drm_backend.cpp b/src/backends/drm/drm_backend.cpp
index f54d8b1fb3..86c6569e27 100644
--- a/src/backends/drm/drm_backend.cpp
+++ b/src/backends/drm/drm_backend.cpp
@@ -215,7 +215,9 @@ bool DrmBackend::initialize()
     } else {
         const auto devices = m_udev->listGPUs();
         for (const UdevDevice::Ptr &device : devices) {
-            addGpu(device->devNode());
+            if (device->seat() == m_session->seat()) {
+                addGpu(device->devNode());
+            }
         }
     }
 
@@ -244,8 +246,16 @@ void DrmBackend::handleUdevEvent()
         if (!m_active) {
             continue;
         }
-        if (!m_explicitGpus.isEmpty() && !m_explicitGpus.contains(device->devNode())) {
-            continue;
+
+        // Ignore the device seat if the KWIN_DRM_DEVICES envvar is set.
+        if (!m_explicitGpus.isEmpty()) {
+            if (!m_explicitGpus.contains(device->devNode())) {
+                continue;
+            }
+        } else {
+            if (device->seat() != m_session->seat()) {
+                continue;
+            }
         }
 
         if (device->action() == QStringLiteral("add")) {
diff --git a/src/utils/udev.cpp b/src/utils/udev.cpp
index 02dec3960e..398fed7d9c 100644
--- a/src/utils/udev.cpp
+++ b/src/utils/udev.cpp
@@ -7,9 +7,6 @@
     SPDX-License-Identifier: GPL-2.0-or-later
 */
 #include "udev.h"
-#include "main.h"
-#include "platform.h"
-#include "session.h"
 #include "utils/common.h"
 // Qt
 #include <QByteArray>
@@ -102,23 +99,14 @@ std::vector<UdevDevice::Ptr> UdevEnumerate::find()
         return {};
     }
     std::vector<UdevDevice::Ptr> vect;
-    QString defaultSeat = QStringLiteral("seat0");
     udev_list_entry *it = udev_enumerate_get_list_entry(m_enumerate.data());
     while (it) {
         auto current = it;
         it = udev_list_entry_get_next(it);
         auto device = m_udev->deviceFromSyspath(udev_list_entry_get_name(current));
-        if (!device) {
-            continue;
+        if (device) {
+            vect.push_back(std::move(device));
         }
-        QString deviceSeat = device->property("ID_SEAT");
-        if (deviceSeat.isEmpty()) {
-            deviceSeat = defaultSeat;
-        }
-        if (deviceSeat != kwinApp()->session()->seat()) {
-            continue;
-        }
-        vect.push_back(std::move(device));
     }
     return vect;
 }
@@ -230,6 +218,15 @@ bool UdevDevice::isBootVga() const
     return systAttrValue && qstrcmp(systAttrValue, "1") == 0;
 }
 
+QString UdevDevice::seat() const
+{
+    QString deviceSeat = udev_device_get_property_value(m_device, "ID_SEAT");
+    if (deviceSeat.isEmpty()) {
+        deviceSeat = QStringLiteral("seat0");
+    }
+    return deviceSeat;
+}
+
 QString UdevDevice::action() const
 {
     return QString::fromLocal8Bit(udev_device_get_action(m_device));
diff --git a/src/utils/udev.h b/src/utils/udev.h
index 96a0c47e9b..9a5538b54f 100644
--- a/src/utils/udev.h
+++ b/src/utils/udev.h
@@ -38,6 +38,7 @@ public:
 
     QMap<QByteArray, QByteArray> properties() const;
     bool isBootVga() const;
+    QString seat() const;
 
     operator udev_device *() const
     {