Re: [PATCH v3] drm/msm/dp: populate connector of struct dp_panel

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Thu 06 Jan 09:15 PST 2022, Kuogee Hsieh wrote:

> We never assign struct dp_panel::connector, instead the connector is
> stored in struct msm_dp::connector. When we run compliance testing test
> case 4.2.2.6 dp_panel_handle_sink_request() won't have a valid edid set

I unfortunately have no idea what test 4.2.2.6 is or how it ends up in
dp_panel_handle_sink_request() with panel->connector being NULL.

Your new commit message is much better, but I still would like to have
something describing why this particular test case triggers this bug,
how does it differ from normal execution, is it a race, does the test
involve failing edid reads???

> in struct dp_panel::edid so we'll try to use the connectors
> real_edid_checksum and hit a NULL pointer dereference error because the
> connector pointer is never assigned.
> 
> Changes in V2:
> -- populate panel connector at msm_dp_modeset_init() instead of at dp_panel_read_sink_caps()
> 
> Changes in V3:
> -- remove unhelpful kernel crash trace commit text
> -- remove renaming dp_display parameter to dp
> 
> Fixes: 7948fe12d47 ("drm/msm/dp: return correct edid checksum after corrupted edid checksum read")
> Signee-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 3449d3f..40a059d 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1499,6 +1499,7 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev,
>  			struct drm_encoder *encoder)
>  {
>  	struct msm_drm_private *priv;
> +	struct dp_display_private *dp_priv;
>  	int ret;
>  
>  	if (WARN_ON(!encoder) || WARN_ON(!dp_display) || WARN_ON(!dev))
> @@ -1507,6 +1508,8 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev,
>  	priv = dev->dev_private;
>  	dp_display->drm_dev = dev;
>  
> +	dp_priv = container_of(dp_display, struct dp_display_private, dp_display);
> +
>  	ret = dp_display_request_irq(dp_display);
>  	if (ret) {
>  		DRM_ERROR("request_irq failed, ret=%d\n", ret);
> @@ -1524,6 +1527,8 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev,
>  		return ret;
>  	}
>  
> +	dp_priv->panel->connector = dp_display->connector;

The placement of this assignment in msm_dp_modeset_init() makes much
more sense than what you had in v1, so I think this looks good.

Thanks,
Bjorn

> +
>  	priv->connectors[priv->num_connectors++] = dp_display->connector;
>  	return 0;
>  }
> -- 
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