Re: [PATCH] drm/mediatek: hdmi: Perform NULL pointer check for mtk_hdmi_conf

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Il 28/10/21 09:43, AngeloGioacchino Del Regno ha scritto:
In commit 41ca9caaae0b ("drm/mediatek: hdmi: Add check for CEA modes only")
a check for CEA modes was added to function mtk_hdmi_bridge_mode_valid()
in order to address possible issues on MT8167; moreover, with commit
c91026a938c2 ("drm/mediatek: hdmi: Add optional limit on maximal HDMI mode clock")
another similar check was introduced.

Unfortunately though, at the time of writing, MT8173 does not provide
any mtk_hdmi_conf structure and this is crashing the kernel with NULL
pointer upon entering mtk_hdmi_bridge_mode_valid(), which happens as
soon as a HDMI cable gets plugged in.

To fix this regression, add a NULL pointer check for hdmi->conf in the
said function, restoring HDMI functionality and avoiding NULL pointer
kernel panics.

Fixes: 41ca9caaae0b ("drm/mediatek: hdmi: Add check for CEA modes only")
Fixes: c91026a938c2 ("drm/mediatek: hdmi: Add optional limit on maximal HDMI mode clock")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
---
  drivers/gpu/drm/mediatek/mtk_hdmi.c | 12 +++++++-----
  1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c
index 5838c44cbf6f..3196189429bc 100644
--- a/drivers/gpu/drm/mediatek/mtk_hdmi.c
+++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c
@@ -1224,12 +1224,14 @@ static int mtk_hdmi_bridge_mode_valid(struct drm_bridge *bridge,
  			return MODE_BAD;
  	}
- if (hdmi->conf->cea_modes_only && !drm_match_cea_mode(mode))
-		return MODE_BAD;
+	if (hdmi->conf) {
+		if (hdmi->conf->cea_modes_only && !drm_match_cea_mode(mode))
+			return MODE_BAD;
- if (hdmi->conf->max_mode_clock &&
-	    mode->clock > hdmi->conf->max_mode_clock)
-		return MODE_CLOCK_HIGH;
+		if (hdmi->conf->max_mode_clock &&
+		    mode->clock > hdmi->conf->max_mode_clock)
+			return MODE_CLOCK_HIGH;
+	}
if (mode->clock < 27000)
  		return MODE_CLOCK_LOW;


Hello, friendly ping!

Can I please get a review (or merge) of this commit?

This is an important fix for a null pointer KP and restores HDMI functionality.

Thanks,
- Angelo



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