From 46c42e55c6e0b08d9e7db989d6a10f073525e999 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Wed, 21 Jul 2021 15:58:01 +0200
Subject: [PATCH] backend/drm: add support for FB_DAMAGE_CLIPS

This allows the kernel to access our buffer damage. Some drivers
can take advantage of this, e.g. for PSR2 panels (Panel Self
Refresh) or for transfer over USB.

Closes: https://github.com/swaywm/wlroots/issues/1267
---
 backend/drm/atomic.c             | 21 +++++++++++++++++++++
 backend/drm/properties.c         |  1 +
 include/backend/drm/properties.h |  3 ++-
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/backend/drm/atomic.c b/backend/drm/atomic.c
index 35dca7d4..a1774f9c 100644
--- a/backend/drm/atomic.c
+++ b/backend/drm/atomic.c
@@ -201,6 +201,18 @@ static bool atomic_crtc_commit(struct wlr_drm_connector *conn,
 		}
 	}
 
+	uint32_t fb_damage_clips = 0;
+	if ((state->committed & WLR_OUTPUT_STATE_DAMAGE) &&
+			crtc->primary->props.fb_damage_clips != 0) {
+		int rects_len;
+		const pixman_box32_t *rects = pixman_region32_rectangles(
+			(pixman_region32_t *)&state->damage, &rects_len);
+		if (drmModeCreatePropertyBlob(drm->fd, rects,
+				sizeof(*rects) * rects_len, &fb_damage_clips) != 0) {
+			wlr_log_errno(WLR_ERROR, "Failed to create FB_DAMAGE_CLIPS property blob");
+		}
+	}
+
 	bool prev_vrr_enabled =
 		output->adaptive_sync_status == WLR_OUTPUT_ADAPTIVE_SYNC_ENABLED;
 	bool vrr_enabled = prev_vrr_enabled;
@@ -235,6 +247,10 @@ static bool atomic_crtc_commit(struct wlr_drm_connector *conn,
 			atomic_add(&atom, crtc->id, crtc->props.vrr_enabled, vrr_enabled);
 		}
 		set_plane_props(&atom, drm, crtc->primary, crtc->id, 0, 0);
+		if (crtc->primary->props.fb_damage_clips != 0) {
+			atomic_add(&atom, crtc->primary->id,
+				crtc->primary->props.fb_damage_clips, fb_damage_clips);
+		}
 		if (crtc->cursor) {
 			if (drm_connector_is_cursor_visible(conn)) {
 				set_plane_props(&atom, drm, crtc->cursor, crtc->id,
@@ -269,6 +285,11 @@ static bool atomic_crtc_commit(struct wlr_drm_connector *conn,
 		rollback_blob(drm, &crtc->gamma_lut, gamma_lut);
 	}
 
+	if (fb_damage_clips != 0 &&
+			drmModeDestroyPropertyBlob(drm->fd, fb_damage_clips) != 0) {
+		wlr_log_errno(WLR_ERROR, "Failed to destroy FB_DAMAGE_CLIPS property blob");
+	}
+
 	return ok;
 }
 
diff --git a/backend/drm/properties.c b/backend/drm/properties.c
index 5581a130..637eb4bd 100644
--- a/backend/drm/properties.c
+++ b/backend/drm/properties.c
@@ -47,6 +47,7 @@ static const struct prop_info plane_info[] = {
 	{ "CRTC_W", INDEX(crtc_w) },
 	{ "CRTC_X", INDEX(crtc_x) },
 	{ "CRTC_Y", INDEX(crtc_y) },
+	{ "FB_DAMAGE_CLIPS", INDEX(fb_damage_clips) },
 	{ "FB_ID", INDEX(fb_id) },
 	{ "IN_FORMATS", INDEX(in_formats) },
 	{ "SRC_H", INDEX(src_h) },
diff --git a/include/backend/drm/properties.h b/include/backend/drm/properties.h
index 9e1fe0b6..bd90871d 100644
--- a/include/backend/drm/properties.h
+++ b/include/backend/drm/properties.h
@@ -59,8 +59,9 @@ union wlr_drm_plane_props {
 		uint32_t crtc_h;
 		uint32_t fb_id;
 		uint32_t crtc_id;
+		uint32_t fb_damage_clips;
 	};
-	uint32_t props[13];
+	uint32_t props[14];
 };
 
 bool get_drm_connector_props(int fd, uint32_t id,