linux-kernel - [PATCH v6 1/9] drm/omap: add sanity plane state check

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Message-Id: <20211018142842.2511200-2-narmstrong@baylibre.com>
Date:   Mon, 18 Oct 2021 16:28:34 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     tomba@...nel.org
Cc:     linux-omap@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, khilman@...libre.com,
        Neil Armstrong <narmstrong@...libre.com>,
        Benoit Parrot <bparrot@...com>
Subject: [PATCH v6 1/9] drm/omap: add sanity plane state check

Call drm_atomic_helper_check_plane_state() from the plane
atomic_check() callback in order to add plane state sanity
checking.

It will permit filtering out totally bad scaling factors, even
if the real check are done later in the atomic commit.

Signed-off-by: Benoit Parrot <bparrot@...com>
Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
---
 drivers/gpu/drm/omapdrm/omap_plane.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c b/drivers/gpu/drm/omapdrm/omap_plane.c
index 512af976b7e9..c3de4f339387 100644
--- a/drivers/gpu/drm/omapdrm/omap_plane.c
+++ b/drivers/gpu/drm/omapdrm/omap_plane.c
@@ -104,12 +104,15 @@ static void omap_plane_atomic_disable(struct drm_plane *plane,
 	dispc_ovl_enable(priv->dispc, omap_plane->id, false);
 }
 
+#define FRAC_16_16(mult, div)    (((mult) << 16) / (div))
+
 static int omap_plane_atomic_check(struct drm_plane *plane,
 				   struct drm_atomic_state *state)
 {
 	struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(state,
 										 plane);
 	struct drm_crtc_state *crtc_state;
+	int ret;
 
 	if (!new_plane_state->fb)
 		return 0;
@@ -127,6 +130,18 @@ static int omap_plane_atomic_check(struct drm_plane *plane,
 	if (!crtc_state->enable)
 		return 0;
 
+	/*
+	 * Note: these are just sanity checks to filter out totally bad scaling
+	 * factors. The real limits must be calculated case by case, and
+	 * unfortunately we currently do those checks only at the commit
+	 * phase in dispc.
+	 */
+	ret = drm_atomic_helper_check_plane_state(new_plane_state, crtc_state,
+						  FRAC_16_16(1, 8), FRAC_16_16(8, 1),
+						  true, true);
+	if (ret)
+		return ret;
+
 	if (new_plane_state->crtc_x < 0 || new_plane_state->crtc_y < 0)
 		return -EINVAL;
 
-- 
2.25.1