radeonsi: hide real modifier export behind AMD_DEBUG

Some applications are not ready to handle multi plane
modifiers.

User who want this feature can use AMD_DEBUG=export_modifier
to enable it again.

Fixes: 0a266f0256 ("radeonsi: really support eglExportDMABUFImageQueryMESA")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/13917
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37433>

docs/envvars.rst

@@ -1786,6 +1786,9 @@ RadeonSI driver environment variables
       Disable tier3 for video decode.
    ``noenctier2``
       Disable tier2 for video encode.
+   ``export_modifier``
+      Export real modifier instead of DRM_FORMAT_MOD_INVALID to user. For example
+      by eglExportDMABUFImageQueryMESA.
 
 r600 driver environment variables
 ---------------------------------

src/gallium/drivers/radeonsi/si_pipe.c

@@ -84,6 +84,7 @@ static const struct debug_named_value radeonsi_debug_options[] = {
 
    {"tmz", DBG(TMZ), "Force allocation of scanout/depth/stencil buffer as encrypted"},
    {"sqtt", DBG(SQTT), "Enable SQTT"},
+   {"export_modifier", DBG(EXPORT_MODIFIER), "Export real modifier instead of DRM_FORMAT_MOD_INVALID"},
 
    DEBUG_NAMED_VALUE_END /* must be last */
 };

src/gallium/drivers/radeonsi/si_pipe.h

@@ -212,6 +212,7 @@ enum
 
    DBG_TMZ,
    DBG_SQTT,
+   DBG_EXPORT_MODIFIER,
 
    DBG_COUNT
 };

src/gallium/drivers/radeonsi/si_texture.c

@@ -674,7 +674,8 @@ static bool si_resource_get_param(struct pipe_screen *screen, struct pipe_contex
     * PIPE_RESOURCE_PARAM_MODIFIER queries.
     */
    if ((param == PIPE_RESOURCE_PARAM_NPLANES || param == PIPE_RESOURCE_PARAM_MODIFIER) &&
-       resource->target != PIPE_BUFFER)
+       resource->target != PIPE_BUFFER &&
+       (sscreen->debug_flags & DBG(EXPORT_MODIFIER)))
          ac_compute_surface_modifier(&sscreen->info, &tex->surface, resource->nr_samples);
 
    switch (param) {