[PATCH v3 1/2] drm/mediatek: fix kernel oops if no crtc is found

From: Michael Walle <mwalle@kernel.org>
To: "Nícolas F . R . A . Prado" <nfraprado@collabora.com>,
	"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>
Cc: "Nancy . Lin" <nancy.lin@mediatek.com>,
	Frank Wunderlich <frank-w@public-files.de>,
	Jitao Shi <jitao.shi@mediatek.com>,
	Stu Hsieh <stu.hsieh@mediatek.com>,
	dri-devel@lists.freedesktop.org,
	linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Michael Walle <mwalle@kernel.org>
Subject: [PATCH v3 1/2] drm/mediatek: fix kernel oops if no crtc is found
Date: Fri,  1 Sep 2023 19:45:56 +0200	[thread overview]
Message-ID: <20230901174557.3617839-1-mwalle@kernel.org> (raw)

drm_crtc_from_index(0) might return NULL if there are no CRTCs
registered at all which will lead to a kernel oops in
mtk_drm_crtc_dma_dev_get(). Add the missing return value check.

Fixes: 0d9eee9118b7 ("drm/mediatek: Add drm ovl_adaptor sub driver for MT8195")
Signed-off-by: Michael Walle <mwalle@kernel.org>
Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Tested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
---
v3:
 - none
v2:
 - collected tags
 - fixed typos
---
 drivers/gpu/drm/mediatek/mtk_drm_drv.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index 93552d76b6e7..2c582498817e 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -420,6 +420,7 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 	struct mtk_drm_private *private = drm->dev_private;
 	struct mtk_drm_private *priv_n;
 	struct device *dma_dev = NULL;
+	struct drm_crtc *crtc;
 	int ret, i, j;
 
 	if (drm_firmware_drivers_only())
@@ -494,7 +495,9 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 	}
 
 	/* Use OVL device for all DMA memory allocations */
-	dma_dev = mtk_drm_crtc_dma_dev_get(drm_crtc_from_index(drm, 0));
+	crtc = drm_crtc_from_index(drm, 0);
+	if (crtc)
+		dma_dev = mtk_drm_crtc_dma_dev_get(crtc);
 	if (!dma_dev) {
 		ret = -ENODEV;
 		dev_err(drm->dev, "Need at least one OVL device\n");
-- 
2.39.2


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