Where no modifiers are exposed, usually linear modifier is assumed.
However, userspace code is starting to expect IN_FORMATS even when the
only supported modifiers are linear [1].

To avoid possible issues, explicitly set the DRM_FORMAT_MOD_LINEAR
modifier.

[1] 
https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/599/diffs?commit_id=5aea1bc522f0874e6cc07f5120fbcf1736706536

Suggested-by: Chris Healy <cphe...@gmail.com>
Signed-off-by: José Expósito <jose.exposit...@gmail.com>

---

v2: Implement format_mod_supported (Simon Ser)
---
 drivers/gpu/drm/vkms/vkms_plane.c | 34 ++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vkms/vkms_plane.c 
b/drivers/gpu/drm/vkms/vkms_plane.c
index 76a06dd92ac1..7e0d021494c3 100644
--- a/drivers/gpu/drm/vkms/vkms_plane.c
+++ b/drivers/gpu/drm/vkms/vkms_plane.c
@@ -20,6 +20,11 @@ static const u32 vkms_plane_formats[] = {
        DRM_FORMAT_XRGB8888
 };
 
+static const u64 vkms_plane_modifiers[] = {
+       DRM_FORMAT_MOD_LINEAR,
+       DRM_FORMAT_MOD_INVALID
+};
+
 static struct drm_plane_state *
 vkms_plane_duplicate_state(struct drm_plane *plane)
 {
@@ -100,12 +105,39 @@ static void vkms_formats_for_plane_type(enum 
drm_plane_type type,
        }
 }
 
+static bool vkms_format_mod_supported(struct drm_plane *plane, u32 format,
+                                     u64 modifier)
+{
+       bool modifier_found = false;
+       unsigned int i;
+       const u32 *formats;
+       int nformats;
+
+       for (i = 0; i < ARRAY_SIZE(vkms_plane_modifiers) - 1; i++) {
+               if (vkms_plane_modifiers[i] == modifier)
+                       modifier_found = true;
+       }
+
+       if (!modifier_found)
+               return false;
+
+       vkms_formats_for_plane_type(plane->type, &formats, &nformats);
+
+       for (i = 0; i < nformats; i++) {
+               if (formats[i] == format)
+                       return true;
+       }
+
+       return false;
+}
+
 static const struct drm_plane_funcs vkms_plane_funcs = {
        .update_plane           = drm_atomic_helper_update_plane,
        .disable_plane          = drm_atomic_helper_disable_plane,
        .reset                  = vkms_plane_reset,
        .atomic_duplicate_state = vkms_plane_duplicate_state,
        .atomic_destroy_state   = vkms_plane_destroy_state,
+       .format_mod_supported   = vkms_format_mod_supported,
 };
 
 static void vkms_plane_atomic_update(struct drm_plane *plane,
@@ -190,7 +222,7 @@ struct vkms_plane *vkms_plane_init(struct vkms_device 
*vkmsdev,
        plane = drmm_universal_plane_alloc(dev, struct vkms_plane, base, 1 << 
index,
                                           &vkms_plane_funcs,
                                           formats, nformats,
-                                          NULL, type, NULL);
+                                          vkms_plane_modifiers, type, NULL);
        if (IS_ERR(plane))
                return plane;
 
-- 
2.25.1

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