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

[Lucas De Marchi]

On Thu, Jan 25, 2018 at 05:52:26PM +0200, Jani Nikula wrote:
> On Thu, 25 Jan 2018, Rodrigo Vivi <rodrigo.vivi at intel.com> 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.")'
> >
> > 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)
> >
> > 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>
> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_bios.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> > index 95f0b310d656..06526b17a011 100644
> > --- a/drivers/gpu/drm/i915/intel_bios.c
> > +++ b/drivers/gpu/drm/i915/intel_bios.c
> > @@ -1116,9 +1116,9 @@ 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 > 0 && vbt_pin < ARRAY_SIZE(cnp_ddc_pin_map)) {
> >  			return cnp_ddc_pin_map[vbt_pin];
> > -		if (vbt_pin > GMBUS_PIN_4_CNP) {
> > +		} else {
> 
> You're going to hate me, but I just realized this will now complain
> about vbt_pin == 0, which I guess is valid for N/A.
> 
> Why are simple things so hard sometimes... :(
> 
> else if (vbt_pin) ?

vpt_pin is unsigned so we are just special-casing the vpt_pin == 0
already. What about stopping doing that by adding it to the array, like
below (to be squashed)

-------
diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 06526b17a011..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 */
@@ -1116,7 +1117,7 @@ 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];
 		} else {
 			DRM_DEBUG_KMS("Ignoring alternate pin: VBT claims DDC pin %d, which is not valid for this platform\n", vbt_pin);
-------


Lucas De Marchi