2 files changed, 44 insertions, 14 deletions

diff --git a/backend/drm/atomic.c b/backend/drm/atomic.c
index 61d2f6e1..40a272a1 100644
--- a/backend/drm/atomic.c
+++ b/backend/drm/atomic.c
@@ -199,14 +199,18 @@ static bool atomic_crtc_move_cursor(struct wlr_drm_backend *drm,
 static bool atomic_crtc_set_gamma(struct wlr_drm_backend *drm,
 		struct wlr_drm_crtc *crtc, uint16_t *r, uint16_t *g, uint16_t *b,
 		uint32_t size) {
-	struct drm_color_lut gamma[size];
-
 	// Fallback to legacy gamma interface when gamma properties are not available
 	// (can happen on older intel gpu's that support gamma but not degamma)
 	if (crtc->props.gamma_lut == 0) {
 		return legacy_iface.crtc_set_gamma(drm, crtc, r, g, b, size);
 	}
 
+	struct drm_color_lut *gamma = malloc(size * sizeof(struct drm_color_lut));
+	if (gamma == NULL) {
+		wlr_log(WLR_ERROR, "Failed to allocate gamma table");
+		return false;
+	}
+
 	for (uint32_t i = 0; i < size; i++) {
 		gamma[i].red = r[i];
 		gamma[i].green = g[i];
@@ -218,10 +222,12 @@ static bool atomic_crtc_set_gamma(struct wlr_drm_backend *drm,
 	}
 
 	if (drmModeCreatePropertyBlob(drm->fd, gamma,
-				sizeof(struct drm_color_lut) * size, &crtc->gamma_lut)) {
+			size * sizeof(struct drm_color_lut), &crtc->gamma_lut)) {
+		free(gamma);
 		wlr_log_errno(WLR_ERROR, "Unable to create property blob");
 		return false;
 	}
+	free(gamma);
 
 	struct atomic atom;
 	atomic_begin(crtc, &atom);
diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index c4674235..9d030dff 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -228,30 +228,54 @@ static bool drm_connector_swap_buffers(struct wlr_output *output,
 	return true;
 }
 
-static void drm_connector_set_gamma(struct wlr_output *output,
-		uint32_t size, uint16_t *r, uint16_t *g, uint16_t *b) {
+static void fill_empty_gamma_table(uint32_t size,
+		uint16_t *r, uint16_t *g, uint16_t *b) {
+	for (uint32_t i = 0; i < size; ++i) {
+		uint16_t val = (uint32_t)0xffff * i / (size - 1);
+		r[i] = g[i] = b[i] = val;
+	}
+}
+
+static uint32_t drm_connector_get_gamma_size(struct wlr_output *output) {
 	struct wlr_drm_connector *conn = (struct wlr_drm_connector *)output;
 	struct wlr_drm_backend *drm = (struct wlr_drm_backend *)output->backend;
-	bool ok;
 
 	if (conn->crtc) {
-		ok = drm->iface->crtc_set_gamma(drm, conn->crtc, r, g, b, size);
-		if (ok) {
-			wlr_output_update_needs_swap(output);
-		}
+		return drm->iface->crtc_get_gamma_size(drm, conn->crtc);
 	}
 
+	return 0;
 }
 
-static uint32_t drm_connector_get_gamma_size(struct wlr_output *output) {
+static bool drm_connector_set_gamma(struct wlr_output *output,
+		uint32_t size, uint16_t *r, uint16_t *g, uint16_t *b) {
 	struct wlr_drm_connector *conn = (struct wlr_drm_connector *)output;
 	struct wlr_drm_backend *drm = (struct wlr_drm_backend *)output->backend;
 
-	if (conn->crtc) {
-		return drm->iface->crtc_get_gamma_size(drm, conn->crtc);
+	if (!conn->crtc) {
+		return false;
 	}
 
-	return 0;
+	uint16_t *reset_table = NULL;
+	if (size == 0) {
+		size = drm_connector_get_gamma_size(output);
+		reset_table = malloc(3 * size * sizeof(uint16_t));
+		if (reset_table == NULL) {
+			wlr_log(WLR_ERROR, "Failed to allocate gamma table");
+			return false;
+		}
+		r = reset_table;
+		g = reset_table + size;
+		b = reset_table + 2 * size;
+		fill_empty_gamma_table(size, r, g, b);
+	}
+
+	bool ok = drm->iface->crtc_set_gamma(drm, conn->crtc, r, g, b, size);
+	if (ok) {
+		wlr_output_update_needs_swap(output);
+	}
+	free(reset_table);
+	return ok;
 }
 
 static bool drm_connector_export_dmabuf(struct wlr_output *output,