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

Hi, Angelo:

AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com 於 2021年12月13日 週一 下午6:02寫道：

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@collabora.com

---

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.

Applied to mediatek-drm-fixes [1], thanks.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?...

Regards, Chun-Kuang.

Thanks,

• Angelo