glx/egl: fix LIBGL_KOPPER_DISABLE

when set, this disables the use of vk swapchains and lets the dri frontend
manage buffers like any other driver

also document some kopper env vars

Acked-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28137>

docs/envvars.rst

@@ -38,6 +38,22 @@ LibGL environment variables
 
    disable DRI3 if set to ``true``.
 
+.. envvar:: LIBGL_KOPPER_DISABLE
+
+   disable vulkan swapchains with zink if set to ``true``.
+   In general, this should not be used unless you know what you are
+   doing. Some examples of "knowing what you are doing" include:
+   - using a VK driver which has no WSI implementation for your display server
+   - profiling the DRI frontend against your VK driver's WSI implementation
+
+.. envvar:: LIBGL_KOPPER_DRI2
+
+   disable DRI3 with zink if set to ``true``.
+   In general, this should not be used unless you know what you are
+   doing. Some examples of "knowing what you are doing" include:
+   - running xrdp
+   - using a VK driver which doesn't support modifiers
+
 Core Mesa environment variables
 -------------------------------
 

src/egl/drivers/dri2/platform_x11.c

@@ -1803,7 +1803,8 @@ EGLBoolean
 dri2_initialize_x11(_EGLDisplay *disp)
 {
    enum dri2_egl_driver_fail status = DRI2_EGL_DRIVER_FAILED;
-   if (disp->Options.ForceSoftware || disp->Options.Zink)
+   if (disp->Options.ForceSoftware ||
+       (disp->Options.Zink && !debug_get_bool_option("LIBGL_KOPPER_DISABLE", false)))
       return dri2_initialize_x11_swrast(disp);
 
 #ifdef HAVE_DRI3

src/egl/drivers/dri2/platform_x11_dri3.c

@@ -635,7 +635,8 @@ dri3_x11_connect(struct dri2_egl_display *dri2_dpy)
    if (!dri2_dpy->driver_name)
       dri2_dpy->driver_name = loader_get_driver_for_fd(dri2_dpy->fd_render_gpu);
 
-   if (!strcmp(dri2_dpy->driver_name, "zink")) {
+   if (!strcmp(dri2_dpy->driver_name, "zink") &&
+       !debug_get_bool_option("LIBGL_KOPPER_DISABLE", false)) {
       close(dri2_dpy->fd_render_gpu);
       return DRI2_EGL_DRIVER_PREFER_ZINK;
    }

src/gallium/targets/dri/target.c

@@ -142,17 +142,13 @@ DEFINE_LOADER_DRM_ENTRYPOINT(lima)
 #endif
 
 #if defined(GALLIUM_ZINK)
-#if DETECT_OS_ANDROID
-DEFINE_LOADER_DRM_ENTRYPOINT(zink);
-#else
 const __DRIextension **__driDriverGetExtensions_zink(void);
 
 PUBLIC const __DRIextension **__driDriverGetExtensions_zink(void)
 {
-   return galliumvk_driver_extensions;
+   return debug_get_bool_option("LIBGL_KOPPER_DISABLE", false) ? galliumdrm_driver_extensions : galliumvk_driver_extensions;
 }
 #endif
-#endif
 
 #if defined(GALLIUM_D3D12)
 DEFINE_LOADER_DRM_ENTRYPOINT(d3d12);

src/glx/dri3_glx.c

@@ -78,6 +78,7 @@
 #include "loader.h"
 #include "loader_dri_helper.h"
 #include "dri2.h"
+#include "util/u_debug.h"
 
 static struct dri3_drawable *
 loader_drawable_to_dri3_drawable(struct loader_dri3_drawable *draw) {
@@ -836,7 +837,7 @@ dri3_create_screen(int screen, struct glx_display * priv)
       goto handle_error;
    }
 
-   if (!strcmp(driverName, "zink")) {
+   if (!strcmp(driverName, "zink") && !debug_get_bool_option("LIBGL_KOPPER_DISABLE", false)) {
       return_zink = true;
       goto handle_error;
    }

src/glx/glxext.c

@@ -907,7 +907,8 @@ __glXInitialize(Display * dpy)
     ** (e.g., those called in AllocAndFetchScreenConfigs).
     */
 #if defined(GLX_USE_DRM)
-   if (glx_direct && glx_accel && !zink) {
+   if (glx_direct && glx_accel &&
+       (!zink || debug_get_bool_option("LIBGL_KOPPER_DISABLE", false))) {
 #if defined(HAVE_DRI3)
       if (!debug_get_bool_option("LIBGL_DRI3_DISABLE", false)) {
          dpyPriv->dri3Display = dri3_create_display(dpy);