radeon: drmGetVersion can return NULL

Do not crash on scenarios where drmGetVersion returns NULL.
Make Radeon driver initialization more robust.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/476

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: David Heidelberg <david.heidelberg@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20402>

src/gallium/drivers/radeonsi/si_pipe.c

@@ -1486,8 +1486,12 @@ static struct pipe_screen *radeonsi_screen_create_impl(struct radeon_winsys *ws,
 
 struct pipe_screen *radeonsi_screen_create(int fd, const struct pipe_screen_config *config)
 {
-   drmVersionPtr version = drmGetVersion(fd);
    struct radeon_winsys *rw = NULL;
+   drmVersionPtr version;
+
+   version = drmGetVersion(fd);
+   if (!version)
+     return NULL;
 
    driParseConfigFiles(config->options, config->options_info, 0, "radeonsi",
                        NULL, NULL, NULL, 0, NULL, 0);

src/gallium/winsys/radeon/drm/radeon_drm_winsys.c

@@ -152,6 +152,9 @@ static bool do_winsys_init(struct radeon_drm_winsys *ws)
 
    /* Get DRM version. */
    version = drmGetVersion(ws->fd);
+   if (!version)
+      return false;
+
    if (version->version_major != 2 ||
        version->version_minor < 50) {
       fprintf(stderr, "%s: DRM version is %d.%d.%d but this driver is "