[PATCH] drm/mediatek: Add valid modifier check

[Justin Green]

Add a check to mtk_drm_mode_fb_create() that rejects any modifier that
is not the AFBC mode supported by MT8195's display overlays.

Tested by booting ChromeOS and verifying the UI works, and by running
the ChromeOS kms_addfb_basic binary, which has a test called
"addfb25-bad-modifier" that attempts to create a framebuffer with the
modifier DRM_FORMAT_MOD_INVALID and verifies the ADDFB2 ioctl returns
EINVAL.

Signed-off-by: Justin Green <greenjustin at chromium.org>
---
 drivers/gpu/drm/mediatek/mtk_drm_drv.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index cd5b18ef7951..2096e8a794ad 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -51,6 +51,13 @@ mtk_drm_mode_fb_create(struct drm_device *dev,
 	if (info->num_planes != 1)
 		return ERR_PTR(-EINVAL);
 
+	if (cmd->modifier[0] &&
+	    cmd->modifier[0] != DRM_FORMAT_MOD_ARM_AFBC(
+					AFBC_FORMAT_MOD_BLOCK_SIZE_32x8 |
+					AFBC_FORMAT_MOD_SPLIT |
+					AFBC_FORMAT_MOD_SPARSE))
+		return ERR_PTR(-EINVAL);
+
 	return drm_gem_fb_create(dev, file, cmd);
 }
 
-- 
2.41.0.162.gfafddb0af9-goog