kdrive/fbdev: Set glvnd vendor even if not explicitly given by the user

This makes it so that glamor glx can properly initialize even
if no glvnd vendor was given explicitly.

This commit and 6b4f7ba
fix the issue described in #1832 (comment)

Now, `FBConfig`s corresponding to the choosen accelerated `EGLDevice`
are choosen by `glXChooseFBConfig`.

Signed-off-by: stefan11111 <stefan11111@shitposting.expert>

Author: stefan11111

hw/kdrive/fbdev/fb_glamor.c

@@ -168,12 +168,26 @@ fbdev_glamor_query_devices_ext(EGLDeviceEXT **devices, EGLint *num_devices)
     return TRUE;
 }
 
+/**
+ * Find the desired EGLDevice for our config.
+ *
+ * If strict == 2, we are looking for EGLDevices with names and,
+ * if a glvnd vendor was passed, an exact match between the
+ * device's name, and the desired vendor.
+ *
+ * If strict == 1, we are looking for EGLDevices with names and,
+ * if a glvnd vendor was passed, a match between the gl vendor library
+ * provider and the desired vendor's library.
+ *
+ * If strict == 0, we accept all devices, even those with no names.
+ *
+ * Regardless of success/failure, and regardless of strictness level,
+ * we save the statically allocated string with the EGLDevice's name
+ * in *out_driver_name, even if that name is NULL.
+ */
 static inline Bool
-fbdev_glamor_egl_device_matches_config(EGLDeviceEXT device, int strict)
+fbdev_glamor_egl_device_matches_config(EGLDeviceEXT device, int strict, const char** out_driver_name)
 {
-    if (strict <= 0 || !fbdev_glvnd_provider) {
-        return TRUE;
-    }
 /**
  * For some reason, this isn't part of the epoxy headers.
  * It is part of EGL/eglext.h, but we can't include that
@@ -187,10 +201,20 @@ fbdev_glamor_egl_device_matches_config(EGLDeviceEXT device, int strict)
 #endif
 
     const char *driver_name = eglQueryDeviceStringEXT(device, EGL_DRIVER_NAME_EXT);
+    *out_driver_name = driver_name;
+
+    if (strict <= 0) {
+        return TRUE;
+    }
+
     if (!driver_name) {
         return FALSE;
     }
 
+    if (!fbdev_glvnd_provider) {
+        return TRUE;
+    }
+
     if (!strcmp(driver_name, fbdev_glvnd_provider)) {
         return TRUE;
     }
@@ -216,10 +240,16 @@ fbdev_glamor_egl_init_display(FbdevScrPriv *scrpriv)
     EGLDeviceEXT *devices = NULL;
     EGLint num_devices = 0;
 
+    /* Statically allocated according to EGL_EXT_device_persistent_id */
+    const char *driver_name = NULL;
+
 #define GLAMOR_EGL_TRY_PLATFORM(platform, native, platform_fallback) \
     scrpriv->display = glamor_egl_get_display2(platform, native, platform_fallback); \
     if (scrpriv->display != EGL_NO_DISPLAY) { \
         if (eglInitialize(scrpriv->display, NULL, NULL)) { \
+            if (driver_name) { \
+                fbdev_glvnd_provider = driver_name; \
+            } \
             free(devices); \
             return TRUE; \
         } \
@@ -230,7 +260,7 @@ fbdev_glamor_egl_init_display(FbdevScrPriv *scrpriv)
     if (fbdev_glamor_query_devices_ext(&devices, &num_devices)) {
 #define GLAMOR_EGL_TRY_PLATFORM_DEVICE(strict) \
         for (uint32_t i = 0; i < num_devices; i++) { \
-            if (fbdev_glamor_egl_device_matches_config(devices[i], strict)) { \
+            if (fbdev_glamor_egl_device_matches_config(devices[i], strict, &driver_name)) { \
                 GLAMOR_EGL_TRY_PLATFORM(EGL_PLATFORM_DEVICE_EXT, devices[i], TRUE); \
             } \
         }