Re: [PATCH 1/2 v2 addendum v2] drm/i915: Allow parsing of variable size child device entries from VBT

[David Weinehall <david.weinehall@linux.intel.com>]

On Wed, Aug 12, 2015 at 05:19:35PM +0300, Jani Nikula wrote:
> On Wed, 12 Aug 2015, David Weinehall <david.weinehall@linux.intel.com> wrote:
> > Some more fixup is needed; the bits from Antti's patch
> > that actually expanded the struct to fully fit the newer
> > versions of the child_device_config was part of the second
> > patch; since that patch hasn't been merged yet we need this bit:
> >
> > This applies on top of the patch you already merged
> > (the Iboost patch will need corresponding adjustment to
> >  remove the changes I split out):
> >
> > Expand common_child_dev_config to be able to fit all information
> > defined by the latest VBT specification.
> >
> > Signed-off-by: David Weinehall <david.weinehall@linux.intel.com>
> > CC: Antti Koskipaa <antti.koskipaa@linux.intel.com>
> > ---
> >  intel_bios.c |    7 ++++++-
> >  intel_bios.h |    4 ++++
> >  2 files changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> > index 990acc20771a..40e2cc4e7419 100644
> > --- a/drivers/gpu/drm/i915/intel_bios.c
> > +++ b/drivers/gpu/drm/i915/intel_bios.c
> > @@ -1038,6 +1038,10 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
> >  		DRM_DEBUG_KMS("No general definition block is found, no devices defined.\n");
> >  		return;
> >  	}
> > +	/* Remember to keep this in sync with child_device_config;
> > +	 * whenever a new feature is added to BDB that causes that
> > +	 * struct to grow this needs to be updated too
> > +	 */
> >  	if (bdb->version < 195) {
> >  		expected_size = 33;
> >  	} else if (bdb->version == 195) {
> > @@ -1051,7 +1055,8 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
> >  	}
> >  
> >  	if (expected_size > sizeof(*p_child)) {
> > -		DRM_ERROR("child_device_config cannot fit in p_child\n");
> > +		DRM_ERROR("child_device_config (size %u) cannot fit in p_child (size %u); bdb->version: %u\n",
> > +			  expected_size, sizeof(*p_child), bdb->version);
> 
> drivers/gpu/drm/i915/intel_bios.c: In function ‘parse_device_mapping’:
> drivers/gpu/drm/i915/intel_bios.c:1058:3: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 3 has type ‘long unsigned int’ [-Wformat=]
>    DRM_ERROR("child_device_config (size %u) cannot fit in p_child (size %u); bdb->version: %u\n",
>    ^
>   CC [M]  drivers/gpu/drm/i915/intel_fifo_underrun.o

Well spotted.  Or rather, stupid of me to forget that sizeof yields
size_t as type, thus necessitating %zu as conversion specifier.

Fixed version:

Expand common_child_dev_config to be able to fit all information
defined by the latest VBT specification.

v2: Use proper conversion specifier for size_t (%zu)

Signed-off-by: David Weinehall <david.weinehall@linux.intel.com>
CC: Antti Koskipaa <antti.koskipaa@linux.intel.com>

 intel_bios.c |    7 ++++++-
 intel_bios.h |    4 ++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 990acc20771a..5673ed53797b 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -1038,6 +1038,10 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
 		DRM_DEBUG_KMS("No general definition block is found, no devices defined.\n");
 		return;
 	}
+	/* Remember to keep this in sync with child_device_config;
+	 * whenever a new feature is added to BDB that causes that
+	 * struct to grow this needs to be updated too
+	 */
 	if (bdb->version < 195) {
 		expected_size = 33;
 	} else if (bdb->version == 195) {
@@ -1051,7 +1055,8 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
 	}
 
 	if (expected_size > sizeof(*p_child)) {
-		DRM_ERROR("child_device_config cannot fit in p_child\n");
+		DRM_ERROR("child_device_config (size %u) cannot fit in p_child (size %zu); bdb->version: %u\n",
+			  expected_size, sizeof(*p_child), bdb->version);
 		return;
 	}
 
diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h
index f7ad6a585129..71cb96f77870 100644
--- a/drivers/gpu/drm/i915/intel_bios.h
+++ b/drivers/gpu/drm/i915/intel_bios.h
@@ -239,6 +239,10 @@ struct common_child_dev_config {
 	u8 not_common2[2];
 	u8 ddc_pin;
 	u16 edid_ptr;
+	u8 obsolete;
+	u8 flags_1;
+	u8 not_common3[13];
+	u8 iboost_level;
 } __packed;
 
 /* This field changes depending on the BDB version, so the most reliable way to
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