[Intel-gfx] [PATCH] drm/i915/bios: filter out invalid DDC pins from VBT child devices

[Chris Wilson]

Quoting Jani Nikula (2018-04-11 13:53:09)
> On Wed, 11 Apr 2018, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > Quoting Jani Nikula (2018-04-11 10:01:46)
> >> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> >> index c5c7530ba157..6db845991a69 100644
> >> --- a/drivers/gpu/drm/i915/intel_bios.c
> >> +++ b/drivers/gpu/drm/i915/intel_bios.c
> >> @@ -1256,7 +1256,6 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
> >>                 return;
> >>  
> >>         aux_channel = child->aux_channel;
> >> -       ddc_pin = child->ddc_pin;
> >
> > Could we scope ddc_pin better?
> 
> I thought I'd leave that for follow-up, scoping aux_channel similarly.
> 
> >
> >>         is_dvi = child->device_type & DEVICE_TYPE_TMDS_DVI_SIGNALING;
> >>         is_dp = child->device_type & DEVICE_TYPE_DISPLAYPORT_OUTPUT;
> >> @@ -1303,9 +1302,15 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
> >>                 DRM_DEBUG_KMS("Port %c is internal DP\n", port_name(port));
> >>  
> >>         if (is_dvi) {
> >> -               info->alternate_ddc_pin = map_ddc_pin(dev_priv, ddc_pin);
> >> -
> >> -               sanitize_ddc_pin(dev_priv, port);
> >> +               ddc_pin = map_ddc_pin(dev_priv, child->ddc_pin);
> >> +               if (intel_gmbus_is_valid_pin(dev_priv, ddc_pin)) {
> >> +                       info->alternate_ddc_pin = ddc_pin;
> >> +                       sanitize_ddc_pin(dev_priv, port);
> >> +               } else {
> >> +                       DRM_DEBUG_KMS("Port %c has invalid DDC pin %d, "
> >> +                                     "reverting to defaults\n",
> >> +                                     port_name(port), ddc_pin);
> >
> > Do we know what the default pin is here?
> 
> It's in intel_hdmi_ddc_pin(). I'd rather not call that from here, as all
> such functions need to be independent of a lot of driver and output
> setup.
> 
> > s/reverting/sticking/?
> >
> > "invalid DDC pin %d in VBT" ? Not sure if that would be clear from the
> > message otherwise.
> 
> It's a debug, it'll be surrounded by other VBT stuff and will include a
> BIOS-related function name.
> 
> So...
> 
>                         DRM_DEBUG_KMS("Port %c has invalid DDC pin %d, "
>                                       "sticking to defaults\n",
>                                       port_name(port), ddc_pin);
> 
> is this fine?

Sure, I just doubted my ability to remember this was VBT ;)
-Chris