[Intel-gfx] [PATCH] drm/i915/cnp: Properly handle VBT ddc pin out of bounds.

[Lucas De Marchi]

On Thu, Jan 25, 2018 at 02:25:24PM -0800, Rodrigo Vivi wrote:
> If the table result is out of bounds on the array map
> there is something really wrong with VBT pin so we don't
> return that vbt_pin, but only return 0 instead.
> 
> This basically reverts commit 'a8e6f3888b05 ("drm/i915/cnp:
> Ignore VBT request for know invalid DDC pin.")'

In this version it's not really a revert anymore as the debug message is
still there. I'd say it fixes, but doesn't revert.

> 
> Also this properly fixes commit 9c3b2689d01f ("drm/i915/cnl:
> Map VBT DDC Pin to BSpec DDC Pin.")
> 
> v2: Do in a way that we don't break other platforms. (Jani)
> 
> v3: Keep debug message (Jani)
> 
> v4: Don't mess with 0 mapping was noticed by Jani and
>     addressed with a simple solution suggested by Lucas
>     that makes this even simpler.
> 
> Fixes: a8e6f3888b05 ("drm/i915/cnp: Ignore VBT request for know invalid DDC pin.")
> Fixes: 9c3b2689d01f ("drm/i915/cnl: Map VBT DDC Pin to BSpec DDC Pin.")
> Cc: Radhakrishna Sripada <radhakrishna.sripada at intel.com>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Cc: Kai Heng Feng <kai.heng.feng at canonical.com>
> Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> Suggested-by: Lucas De Marchi <lucas.demarchi at intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>

Not sure about the suggested-by vs reviewed-by, but:
Reviewed-by: Lucas De Marchi <lucas.demarchi at intel.com>


Lucas De Marchi

> ---
>  drivers/gpu/drm/i915/intel_bios.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index 95f0b310d656..cf3f8f1ba6f7 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -1107,6 +1107,7 @@ static void sanitize_aux_ch(struct drm_i915_private *dev_priv,
>  }
>  
>  static const u8 cnp_ddc_pin_map[] = {
> +	[0] = 0, /* N/A */
>  	[DDC_BUS_DDI_B] = GMBUS_PIN_1_BXT,
>  	[DDC_BUS_DDI_C] = GMBUS_PIN_2_BXT,
>  	[DDC_BUS_DDI_D] = GMBUS_PIN_4_CNP, /* sic */
> @@ -1116,9 +1117,9 @@ static const u8 cnp_ddc_pin_map[] = {
>  static u8 map_ddc_pin(struct drm_i915_private *dev_priv, u8 vbt_pin)
>  {
>  	if (HAS_PCH_CNP(dev_priv)) {
> -		if (vbt_pin > 0 && vbt_pin < ARRAY_SIZE(cnp_ddc_pin_map))
> +		if (vbt_pin < ARRAY_SIZE(cnp_ddc_pin_map)) {
>  			return cnp_ddc_pin_map[vbt_pin];
> -		if (vbt_pin > GMBUS_PIN_4_CNP) {
> +		} else {
>  			DRM_DEBUG_KMS("Ignoring alternate pin: VBT claims DDC pin %d, which is not valid for this platform\n", vbt_pin);
>  			return 0;
>  		}
> -- 
> 2.13.6
>