[PATCH v5 7/7] libweston: fbdev: Follow the same logic as compositor-drm, and favor the boot_vga device

[nerdopolis]

virtual framebuffer devices that are created by a modesetting driver have the same parent
as the drm card devices.
---
 libweston/compositor-fbdev.c | 40 ++++++++++++++++++++++++++++++++++------
 1 file changed, 34 insertions(+), 6 deletions(-)

diff --git a/libweston/compositor-fbdev.c b/libweston/compositor-fbdev.c
index 34e6c2f3..139d6624 100644
--- a/libweston/compositor-fbdev.c
+++ b/libweston/compositor-fbdev.c
@@ -717,8 +717,8 @@ find_framebuffer_device(struct fbdev_backend *b, const char *seat)
 	struct udev_enumerate *e;
 	struct udev_list_entry *entry;
 	const char *path, *device_seat;
-	char *fb_device;
-	struct udev_device *device;
+	char *fb_device, *find_device, *id;
+	struct udev_device *device, *pci;
 
 	e = udev_enumerate_new(b->udev);
 	udev_enumerate_add_match_subsystem(e, "graphics");
@@ -727,20 +727,48 @@ find_framebuffer_device(struct fbdev_backend *b, const char *seat)
 	udev_enumerate_scan_devices(e);
 	fb_device = NULL;
 	udev_list_entry_foreach(entry, udev_enumerate_get_list_entry(e)) {
+		bool is_boot_vga = false;
 
 		path = udev_list_entry_get_name(entry);
 		device = udev_device_new_from_syspath(b->udev, path);
+		find_device = udev_device_get_devnode(device);
 		if (!device)
 			continue;
 		device_seat = udev_device_get_property_value(device, "ID_SEAT");
 		if (!device_seat)
 			device_seat = default_seat;
-		if (!strcmp(device_seat, seat)) {
-			fb_device = udev_device_get_devnode(device);
-			udev_enumerate_unref(e);
+		if (strcmp(device_seat, seat)) {
+			udev_device_unref(device);
+			continue;
+		}
+
+		pci = udev_device_get_parent_with_subsystem_devtype(device,
+								"pci", NULL);
+		if (pci) {
+			id = udev_device_get_sysattr_value(pci, "boot_vga");
+			if (id && !strcmp(id, "1"))
+				is_boot_vga = true;
+		}
+
+		/* If a framebuffer device was found, and this device isn't
+		 * the boot-VGA device, don't use it. */
+		if (!is_boot_vga && fb_device) {
+			udev_device_unref(device);
+			continue;
+		}
+
+		/* There can only be one boot_vga device. Try to use it
+		 * at all costs. */
+		if (is_boot_vga) {
+			fb_device = find_device;
 			break;
 		}
-		udev_device_unref(device);
+
+		/* Per the (!is_boot_vga && fb_device) test above, only
+		 * trump existing saved devices with boot-VGA devices, so if
+		 * the test ends up here, this must be the first device seen. */
+		assert(!fb_device);
+		fb_device = find_device;
 	}
 
 	udev_enumerate_unref(e);
-- 
2.14.1