render/vulkan: prefer render node for wlr_renderer_get_drm_fd()

Instead of returning a primary node from wlr_renderer_get_drm_fd(),
prefer to return a render node if any.

include/render/vulkan.h

@@ -66,6 +66,7 @@ struct wlr_vk_device {
 // Tries to find the VkPhysicalDevice for the given drm fd.
 // Might find none and return VK_NULL_HANDLE.
 VkPhysicalDevice vulkan_find_drm_phdev(struct wlr_vk_instance *ini, int drm_fd);
+int vulkan_open_phdev_drm_fd(VkPhysicalDevice phdev);
 
 // Creates a device for the given instance and physical device.
 struct wlr_vk_device *vulkan_device_create(struct wlr_vk_instance *ini,

render/vulkan/renderer.c

@@ -2240,10 +2240,10 @@ struct wlr_renderer *wlr_vk_renderer_create_with_drm_fd(int drm_fd) {
 		return NULL;
 	}
 
-	// We duplicate it so it's not closed while we still need it.
-	dev->drm_fd = fcntl(drm_fd, F_DUPFD_CLOEXEC, 0);
+	// Do not use the drm_fd that was passed in: we should prefer the render
+	// node even if a primary node was provided
+	dev->drm_fd = vulkan_open_phdev_drm_fd(phdev);
 	if (dev->drm_fd < 0) {
-		wlr_log_errno(WLR_ERROR, "fcntl(F_DUPFD_CLOEXEC) failed");
 		vulkan_device_destroy(dev);
 		vulkan_instance_destroy(ini);
 		return NULL;

render/vulkan/vulkan.c

@@ -1,4 +1,8 @@
+#if !defined(__FreeBSD__)
+#define _POSIX_C_SOURCE 200809L
+#endif
 #include <assert.h>
+#include <fcntl.h>
 #include <math.h>
 #include <stdlib.h>
 #include <stdint.h>
@@ -366,6 +370,52 @@ VkPhysicalDevice vulkan_find_drm_phdev(struct wlr_vk_instance *ini, int drm_fd)
 	return VK_NULL_HANDLE;
 }
 
+int vulkan_open_phdev_drm_fd(VkPhysicalDevice phdev) {
+	// vulkan_find_drm_phdev() already checks that VK_EXT_physical_device_drm
+	// is supported
+	VkPhysicalDeviceDrmPropertiesEXT drm_props = {
+		.sType = VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_DRM_PROPERTIES_EXT,
+	};
+	VkPhysicalDeviceProperties2 props = {
+		.sType = VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_PROPERTIES_2,
+		.pNext = &drm_props,
+	};
+	vkGetPhysicalDeviceProperties2(phdev, &props);
+
+	dev_t devid;
+	if (drm_props.hasRender) {
+		devid = makedev(drm_props.renderMajor, drm_props.renderMinor);
+	} else if (drm_props.hasPrimary) {
+		devid = makedev(drm_props.primaryMajor, drm_props.primaryMinor);
+	} else {
+		wlr_log(WLR_ERROR, "Physical device is missing both render and primary nodes");
+		return -1;
+	}
+
+	drmDevice *device = NULL;
+	if (drmGetDeviceFromDevId(devid, 0, &device) != 0) {
+		wlr_log_errno(WLR_ERROR, "drmGetDeviceFromDevId failed");
+		return -1;
+	}
+
+	const char *name = NULL;
+	if (device->available_nodes & (1 << DRM_NODE_RENDER)) {
+		name = device->nodes[DRM_NODE_RENDER];
+	} else {
+		assert(device->available_nodes & (1 << DRM_NODE_PRIMARY));
+		name = device->nodes[DRM_NODE_PRIMARY];
+		wlr_log(WLR_DEBUG, "DRM device %s has no render node, "
+			"falling back to primary node", name);
+	}
+
+	int drm_fd = open(name, O_RDWR | O_NONBLOCK | O_CLOEXEC);
+	if (drm_fd < 0) {
+		wlr_log_errno(WLR_ERROR, "Failed to open DRM node %s", name);
+	}
+	drmFreeDevice(&device);
+	return drm_fd;
+}
+
 static void load_device_proc(struct wlr_vk_device *dev, const char *name,
 		void *proc_ptr) {
 	void *proc = (void *)vkGetDeviceProcAddr(dev->dev, name);