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From: Wojciech Macek <wmacek@chromium.org>
To: Chun-Kuang Hu <chunkuang.hu@kernel.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	David Airlie <airlied@gmail.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>,
	dri-devel@lists.freedesktop.org,
	linux-mediatek@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	chrome-platform@lists.linux.dev
Cc: Wojciech Macek <wmacek@chromium.com>
Subject: [PATCH] drm/mediatek/dp: fix mtk_dp_aux_transfer return value
Date: Tue,  2 Apr 2024 07:11:13 +0000
Message-ID: <20240402071113.3135903-1-wmacek@chromium.org>
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From: Wojciech Macek <wmacek@chromium.com>

In case there is no DP device attached to the port the
transfer function should return IO error, similar to what
other drivers do.
In case EAGAIN is returned then any read from /dev/drm_dp_aux
device ends up in an infinite loop as the upper layers
constantly repeats the transfer request.

Signed-off-by: Wojciech Macek <wmacek@chromium.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 0ba72102636a..536366956447 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -2104,7 +2104,7 @@ static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,
 
 	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP &&
 	    !mtk_dp->train_info.cable_plugged_in) {
-		ret = -EAGAIN;
+		ret = -EIO;
 		goto err;
 	}
 
-- 
2.44.0.478.gd926399ef9-goog