linux-kernel - [PATCH] drm/panel: novatek-nt35950: Improve error handling

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Message-Id: <20230415-konrad-longbois-next-v1-1-ce695dc9df84@linaro.org>
Date:   Sat, 15 Apr 2023 13:00:30 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Neil Armstrong <neil.armstrong@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     Marijn Suijten <marijn.suijten@...ainline.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Konrad Dybcio <konrad.dybcio@...aro.org>
Subject: [PATCH] drm/panel: novatek-nt35950: Improve error handling

In a very peculiar case when probing and registering with the secondary
DSI host succeeds, but the OF backlight or DSI attachment fails, the
primary DSI device is automatically cleaned up, but the secondary one
is not, leading to -EEXIST when the driver core tries to handle
-EPROBE_DEFER.

Unregister the DSI1 device manually on failure to prevent that.

Fixes: 623a3531e9cf ("drm/panel: Add driver for Novatek NT35950 DSI DriverIC panels")
Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
---
 drivers/gpu/drm/panel/panel-novatek-nt35950.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panel/panel-novatek-nt35950.c b/drivers/gpu/drm/panel/panel-novatek-nt35950.c
index abf752b36a52..7498fc6258bb 100644
--- a/drivers/gpu/drm/panel/panel-novatek-nt35950.c
+++ b/drivers/gpu/drm/panel/panel-novatek-nt35950.c
@@ -585,8 +585,11 @@ static int nt35950_probe(struct mipi_dsi_device *dsi)
 		       DRM_MODE_CONNECTOR_DSI);
 
 	ret = drm_panel_of_backlight(&nt->panel);
-	if (ret)
+	if (ret) {
+		mipi_dsi_device_unregister(nt->dsi[1]);
+
 		return dev_err_probe(dev, ret, "Failed to get backlight\n");
+	}
 
 	drm_panel_add(&nt->panel);
 
@@ -602,6 +605,9 @@ static int nt35950_probe(struct mipi_dsi_device *dsi)
 
 		ret = mipi_dsi_attach(nt->dsi[i]);
 		if (ret < 0) {
+			/* If we fail to attach to either host, we're done */
+			mipi_dsi_device_unregister(nt->dsi[1]);
+
 			return dev_err_probe(dev, ret,
 					     "Cannot attach to DSI%d host.\n", i);
 		}

---
base-commit: 035ba5f9cf511b9299fd9c9d0688ef930d33c886
change-id: 20230415-konrad-longbois-next-847d57abb4d2

Best regards,
-- 
Konrad Dybcio <konrad.dybcio@...aro.org>