The LINEAR modifier is advertised as default if a driver doesn't specify
modifiers. However, there are legacy drivers such as radeon that do not
support modifiers but infer the actual layout of the underlying buffer.
Therefore, a new flag not_support_fb_modifires is introduced for these
legacy drivers. Allow_fb_modifiers will be replaced with this new flag.

Signed-off-by: Tomohito Esaki <e...@igel.co.jp>
---
 drivers/gpu/drm/drm_plane.c   | 34 ++++++++++++++++++++++++++--------
 include/drm/drm_mode_config.h | 10 ++++++++++
 include/drm/drm_plane.h       |  3 +++
 3 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
index 82afb854141b..75308ee240c0 100644
--- a/drivers/gpu/drm/drm_plane.c
+++ b/drivers/gpu/drm/drm_plane.c
@@ -161,6 +161,16 @@ modifiers_ptr(struct drm_format_modifier_blob *blob)
        return (struct drm_format_modifier *)(((char *)blob) + 
blob->modifiers_offset);
 }
 
+static bool check_format_modifier(struct drm_plane *plane, uint32_t format,
+                                 uint64_t modifier)
+{
+       if (plane->funcs->format_mod_supported)
+               return plane->funcs->format_mod_supported(plane, format,
+                                                         modifier);
+
+       return modifier == DRM_FORMAT_MOD_LINEAR;
+}
+
 static int create_in_format_blob(struct drm_device *dev, struct drm_plane 
*plane)
 {
        const struct drm_mode_config *config = &dev->mode_config;
@@ -203,16 +213,15 @@ static int create_in_format_blob(struct drm_device *dev, 
struct drm_plane *plane
        memcpy(formats_ptr(blob_data), plane->format_types, formats_size);
 
        /* If we can't determine support, just bail */
-       if (!plane->funcs->format_mod_supported)
+       if (config->fb_modifiers_not_supported)
                goto done;
 
        mod = modifiers_ptr(blob_data);
        for (i = 0; i < plane->modifier_count; i++) {
                for (j = 0; j < plane->format_count; j++) {
-                       if (plane->funcs->format_mod_supported(plane,
-                                                              
plane->format_types[j],
-                                                              
plane->modifiers[i])) {
-
+                       if (check_format_modifier(plane,
+                                                 plane->format_types[j],
+                                                 plane->modifiers[i])) {
                                mod->formats |= 1ULL << j;
                        }
                }
@@ -242,6 +251,10 @@ static int __drm_universal_plane_init(struct drm_device 
*dev,
                                      const char *name, va_list ap)
 {
        struct drm_mode_config *config = &dev->mode_config;
+       const uint64_t default_modifiers[] = {
+               DRM_FORMAT_MOD_LINEAR,
+               DRM_FORMAT_MOD_INVALID
+       };
        unsigned int format_modifier_count = 0;
        int ret;
 
@@ -282,6 +295,11 @@ static int __drm_universal_plane_init(struct drm_device 
*dev,
 
                while (*temp_modifiers++ != DRM_FORMAT_MOD_INVALID)
                        format_modifier_count++;
+       } else {
+               if (!dev->mode_config.fb_modifiers_not_supported) {
+                       format_modifiers = default_modifiers;
+                       format_modifier_count = 1;
+               }
        }
 
        /* autoset the cap and check for consistency across all planes */
@@ -346,7 +364,7 @@ static int __drm_universal_plane_init(struct drm_device 
*dev,
                drm_object_attach_property(&plane->base, config->prop_src_h, 0);
        }
 
-       if (config->allow_fb_modifiers)
+       if (format_modifier_count)
                create_in_format_blob(dev, plane);
 
        return 0;
@@ -373,8 +391,8 @@ static int __drm_universal_plane_init(struct drm_device 
*dev,
  * drm_universal_plane_init() to let the DRM managed resource infrastructure
  * take care of cleanup and deallocation.
  *
- * Drivers supporting modifiers must set @format_modifiers on all their planes,
- * even those that only support DRM_FORMAT_MOD_LINEAR.
+ * For drivers supporting modifiers, all planes will advertise
+ * DRM_FORMAT_MOD_LINEAR support, if @format_modifiers is not set.
  *
  * Returns:
  * Zero on success, error code on failure.
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index 48b7de80daf5..c56f298c55bd 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -920,6 +920,16 @@ struct drm_mode_config {
         */
        bool allow_fb_modifiers;
 
+       /**
+        * @fb_modifiers_not_supported:
+        *
+        * This flag is for legacy drivers such as radeon that do not support
+        * modifiers but infer the actual layout of the underlying buffer.
+        * Generally, each drivers must support modifiers, this flag should not
+        * be set.
+        */
+       bool fb_modifiers_not_supported;
+
        /**
         * @normalize_zpos:
         *
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index 0c1102dc4d88..cad641b1f797 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -803,6 +803,9 @@ void *__drmm_universal_plane_alloc(struct drm_device *dev,
  *
  * The @drm_plane_funcs.destroy hook must be NULL.
  *
+ * For drivers supporting modifiers, all planes will advertise
+ * DRM_FORMAT_MOD_LINEAR support, if @format_modifiers is not set.
+ *
  * Returns:
  * Pointer to new plane, or ERR_PTR on failure.
  */
-- 
2.17.1

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