From dfedd67148d4128aff99cbd417e9f7d0bd210555 Mon Sep 17 00:00:00 2001
From: Tom Englund <tomenglund26@gmail.com>
Date: Sat, 19 Jul 2025 01:35:31 +0200
Subject: [PATCH] core: add a rendernode fallback

if no matching rendernode is found, fallback to first available.
---
 src/backend/Session.cpp | 53 +++++++++++++++++++++++++++++++----------
 1 file changed, 40 insertions(+), 13 deletions(-)

diff --git a/src/backend/Session.cpp b/src/backend/Session.cpp
index 7fa4604..b8608ad 100644
--- a/src/backend/Session.cpp
+++ b/src/backend/Session.cpp
@@ -165,13 +165,8 @@ void Aquamarine::CSessionDevice::resolveMatchingRenderNode(struct udev_device* c
     if (!cardDevice)
         return;
 
-    auto pciParent = udev_device_get_parent_with_subsystem_devtype(cardDevice, "pci", nullptr);
-    if (!pciParent)
-        return;
-
-    const char* pciSyspath = udev_device_get_syspath(pciParent);
-    if (!pciSyspath)
-        return;
+    auto                   pciParent  = udev_device_get_parent_with_subsystem_devtype(cardDevice, "pci", nullptr);
+    const auto*            pciSyspath = pciParent ? udev_device_get_syspath(pciParent) : nullptr;
 
     struct udev_enumerate* enumerate = udev_enumerate_new(session->udevHandle);
     if (!enumerate)
@@ -183,25 +178,30 @@ void Aquamarine::CSessionDevice::resolveMatchingRenderNode(struct udev_device* c
     struct udev_list_entry* devices = udev_enumerate_get_list_entry(enumerate);
     struct udev_list_entry* entry   = nullptr;
 
+    bool                    matched = false;
+
     udev_list_entry_foreach(entry, devices) {
-        const char*         path = udev_list_entry_get_name(entry);
-        struct udev_device* dev  = udev_device_new_from_syspath(session->udevHandle, path);
+        const auto* path = udev_list_entry_get_name(entry);
+        auto        dev  = udev_device_new_from_syspath(session->udevHandle, path);
         if (!dev)
             continue;
 
-        const char* devnode = udev_device_get_devnode(dev);
-        const char* devtype = udev_device_get_devtype(dev);
+        const auto* devnode = udev_device_get_devnode(dev);
+        const auto* devtype = udev_device_get_devtype(dev);
 
         if (!devnode || !devtype || strcmp(devtype, "drm_minor") != 0 || !strstr(devnode, "renderD")) {
             udev_device_unref(dev);
             continue;
         }
 
-        struct udev_device* devParent = udev_device_get_parent_with_subsystem_devtype(dev, "pci", nullptr);
-        if (devParent && strcmp(udev_device_get_syspath(devParent), pciSyspath) == 0) {
+        auto devParent = udev_device_get_parent_with_subsystem_devtype(dev, "pci", nullptr);
+        if (devParent && pciSyspath && strcmp(udev_device_get_syspath(devParent), pciSyspath) == 0) {
             renderNodeFd = open(devnode, O_RDWR | O_CLOEXEC);
             if (renderNodeFd < 0)
                 session->backend->log(AQ_LOG_WARNING, std::format("drm: Failed to open matching render node {}", devnode));
+            else
+                matched = true;
+
             udev_device_unref(dev);
             break;
         }
@@ -209,6 +209,33 @@ void Aquamarine::CSessionDevice::resolveMatchingRenderNode(struct udev_device* c
         udev_device_unref(dev);
     }
 
+    if (!matched) {
+        // fallback to the first render node
+        udev_list_entry_foreach(entry, devices) {
+            const auto* path = udev_list_entry_get_name(entry);
+            auto        dev  = udev_device_new_from_syspath(session->udevHandle, path);
+            if (!dev)
+                continue;
+
+            const auto* devnode = udev_device_get_devnode(dev);
+            const auto* devtype = udev_device_get_devtype(dev);
+
+            if (!devnode || !devtype || strcmp(devtype, "drm_minor") != 0 || !strstr(devnode, "renderD")) {
+                udev_device_unref(dev);
+                continue;
+            }
+
+            renderNodeFd = open(devnode, O_RDWR | O_CLOEXEC);
+            if (renderNodeFd >= 0) {
+                session->backend->log(AQ_LOG_WARNING, std::format("drm: No matching render node for {}, falling back to {}", path, devnode));
+                udev_device_unref(dev);
+                break;
+            }
+
+            udev_device_unref(dev);
+        }
+    }
+
     udev_enumerate_unref(enumerate);
 }