linux-kernel - [PATCH v1 1/1] drm/mediatek: Add return value check when reading DPCD

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Message-ID: <20240930092000.5385-1-liankun.yang@mediatek.com>
Date: Mon, 30 Sep 2024 17:17:41 +0800
From: Liankun Yang <liankun.yang@...iatek.com>
To: <chunkuang.hu@...nel.org>, <p.zabel@...gutronix.de>, <airlied@...il.com>,
	<simona@...ll.ch>, <matthias.bgg@...il.com>,
	<angelogioacchino.delregno@...labora.com>, <msp@...libre.com>,
	<rex-bc.chen@...iatek.com>, <dmitry.osipenko@...labora.com>,
	<ck.hu@...iatek.com>, <jitao.shi@...iatek.com>, <mac.shen@...iatek.com>,
	<peng.liu@...iatek.com>, <liankun.yang@...iatek.com>
CC: <Project_Global_Chrome_Upstream_Group@...iatek.com>,
	<dri-devel@...ts.freedesktop.org>, <linux-mediatek@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: [PATCH v1 1/1] drm/mediatek: Add return value check when reading DPCD

Returns the number of bytes transferred (1) on success.
Check the return value to confirm that AUX communication is successful.

Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort driver")

Signed-off-by: Liankun Yang <liankun.yang@...iatek.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index d8796a904eca..3cab65345d1e 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -2018,6 +2018,7 @@ static enum drm_connector_status mtk_dp_bdg_detect(struct drm_bridge *bridge)
 	enum drm_connector_status ret = connector_status_disconnected;
 	bool enabled = mtk_dp->enabled;
 	u8 sink_count = 0;
+	size_t value;
 
 	if (!mtk_dp->train_info.cable_plugged_in)
 		return ret;
@@ -2032,7 +2033,12 @@ static enum drm_connector_status mtk_dp_bdg_detect(struct drm_bridge *bridge)
 	 * function, we just need to check the HPD connection to check
 	 * whether we connect to a sink device.
 	 */
-	drm_dp_dpcd_readb(&mtk_dp->aux, DP_SINK_COUNT, &sink_count);
+	value = drm_dp_dpcd_readb(&mtk_dp->aux, DP_SINK_COUNT, &sink_count);
+	if (value < 0) {
+		drm_err(mtk_dp->drm_dev, "Failed to read DP Sink Count: %zd\n", value);
+		return ret;
+	}
+
 	if (DP_GET_SINK_COUNT(sink_count))
 		ret = connector_status_connected;
 
-- 
2.45.2