[v2] drm/i915: constify validate_vbt in VBT parsing
diff mbox

Message ID 1431434492-26300-1-git-send-email-jani.nikula@intel.com
State New
Headers show

Commit Message

Jani Nikula May 12, 2015, 12:41 p.m. UTC
Make input and output of validate_vbt const, and fix the fallout. We
shouldn't modify the VBT, so make the compiler help us here.

v2: use pointer arithmetics on void* to simplify (Ville)

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/intel_bios.c | 49 ++++++++++++++++++++-------------------
 1 file changed, 25 insertions(+), 24 deletions(-)

Comments

Ville Syrjala May 12, 2015, 12:53 p.m. UTC | #1
On Tue, May 12, 2015 at 03:41:32PM +0300, Jani Nikula wrote:
> Make input and output of validate_vbt const, and fix the fallout. We
> shouldn't modify the VBT, so make the compiler help us here.
> 
> v2: use pointer arithmetics on void* to simplify (Ville)
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/intel_bios.c | 49 ++++++++++++++++++++-------------------
>  1 file changed, 25 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index 5876e7cb132d..cbd16c01959a 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -205,7 +205,7 @@ get_lvds_fp_timing(const struct bdb_header *bdb,
>  /* Try to find integrated panel data */
>  static void
>  parse_lfp_panel_data(struct drm_i915_private *dev_priv,
> -			    struct bdb_header *bdb)
> +		     const struct bdb_header *bdb)
>  {
>  	const struct bdb_lvds_options *lvds_options;
>  	const struct bdb_lvds_lfp_data *lvds_lfp_data;
> @@ -311,7 +311,8 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv,
>  }
>  
>  static void
> -parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
> +parse_lfp_backlight(struct drm_i915_private *dev_priv,
> +		    const struct bdb_header *bdb)
>  {
>  	const struct bdb_lfp_backlight_data *backlight_data;
>  	const struct bdb_lfp_backlight_data_entry *entry;
> @@ -349,7 +350,7 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
>  /* Try to find sdvo panel data */
>  static void
>  parse_sdvo_panel_data(struct drm_i915_private *dev_priv,
> -		      struct bdb_header *bdb)
> +		      const struct bdb_header *bdb)
>  {
>  	const struct lvds_dvo_timing *dvo_timing;
>  	struct drm_display_mode *panel_fixed_mode;
> @@ -403,7 +404,7 @@ static int intel_bios_ssc_frequency(struct drm_device *dev,
>  
>  static void
>  parse_general_features(struct drm_i915_private *dev_priv,
> -		       struct bdb_header *bdb)
> +		       const struct bdb_header *bdb)
>  {
>  	struct drm_device *dev = dev_priv->dev;
>  	const struct bdb_general_features *general;
> @@ -429,7 +430,7 @@ parse_general_features(struct drm_i915_private *dev_priv,
>  
>  static void
>  parse_general_definitions(struct drm_i915_private *dev_priv,
> -			  struct bdb_header *bdb)
> +			  const struct bdb_header *bdb)
>  {
>  	const struct bdb_general_definitions *general;
>  
> @@ -456,7 +457,7 @@ child_device_ptr(const struct bdb_general_definitions *p_defs, int i)
>  
>  static void
>  parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
> -			  struct bdb_header *bdb)
> +			  const struct bdb_header *bdb)
>  {
>  	struct sdvo_device_mapping *p_mapping;
>  	const struct bdb_general_definitions *p_defs;
> @@ -546,7 +547,7 @@ parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
>  
>  static void
>  parse_driver_features(struct drm_i915_private *dev_priv,
> -		       struct bdb_header *bdb)
> +		      const struct bdb_header *bdb)
>  {
>  	const struct bdb_driver_features *driver;
>  
> @@ -572,7 +573,7 @@ parse_driver_features(struct drm_i915_private *dev_priv,
>  }
>  
>  static void
> -parse_edp(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
> +parse_edp(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
>  {
>  	const struct bdb_edp *edp;
>  	const struct edp_power_seq *edp_pps;
> @@ -684,7 +685,7 @@ parse_edp(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
>  }
>  
>  static void
> -parse_psr(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
> +parse_psr(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
>  {
>  	const struct bdb_psr *psr;
>  	const struct psr_table *psr_table;
> @@ -795,7 +796,7 @@ static u8 *goto_next_sequence(u8 *data, int *size)
>  }
>  
>  static void
> -parse_mipi(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
> +parse_mipi(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
>  {
>  	const struct bdb_mipi_config *start;
>  	const struct bdb_mipi_sequence *sequence;
> @@ -946,7 +947,7 @@ err:
>  }
>  
>  static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
> -			   struct bdb_header *bdb)
> +			   const struct bdb_header *bdb)
>  {
>  	union child_device_config *it, *child = NULL;
>  	struct ddi_vbt_port_info *info = &dev_priv->vbt.ddi_port_info[port];
> @@ -1048,7 +1049,7 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
>  }
>  
>  static void parse_ddi_ports(struct drm_i915_private *dev_priv,
> -			    struct bdb_header *bdb)
> +			    const struct bdb_header *bdb)
>  {
>  	struct drm_device *dev = dev_priv->dev;
>  	enum port port;
> @@ -1068,7 +1069,7 @@ static void parse_ddi_ports(struct drm_i915_private *dev_priv,
>  
>  static void
>  parse_device_mapping(struct drm_i915_private *dev_priv,
> -		       struct bdb_header *bdb)
> +		     const struct bdb_header *bdb)
>  {
>  	const struct bdb_general_definitions *p_defs;
>  	const union child_device_config *p_child;
> @@ -1198,19 +1199,20 @@ static const struct dmi_system_id intel_no_opregion_vbt[] = {
>  	{ }
>  };
>  
> -static struct bdb_header *validate_vbt(char *base, size_t size,
> -				       struct vbt_header *vbt,
> -				       const char *source)
> +static const struct bdb_header *validate_vbt(const void *base, size_t size,
> +					     const void *_vbt,
> +					     const char *source)
>  {
> +	const struct vbt_header *vbt = _vbt;
>  	size_t offset;
> -	struct bdb_header *bdb;
> +	const struct bdb_header *bdb;
>  
>  	if (vbt == NULL) {
>  		DRM_DEBUG_DRIVER("VBT signature missing\n");
>  		return NULL;
>  	}
>  
> -	offset = (char *)vbt - base;
> +	offset = _vbt - base;
>  	if (offset + sizeof(struct vbt_header) > size) {
>  		DRM_DEBUG_DRIVER("VBT header incomplete\n");
>  		return NULL;
> @@ -1227,7 +1229,7 @@ static struct bdb_header *validate_vbt(char *base, size_t size,
>  		return NULL;
>  	}
>  
> -	bdb = (struct bdb_header *)(base + offset);
> +	bdb = base + offset;
>  	if (offset + bdb->bdb_size > size) {
>  		DRM_DEBUG_DRIVER("BDB incomplete\n");
>  		return NULL;
> @@ -1252,7 +1254,7 @@ intel_parse_bios(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct pci_dev *pdev = dev->pdev;
> -	struct bdb_header *bdb = NULL;
> +	const struct bdb_header *bdb = NULL;
>  	u8 __iomem *bios = NULL;
>  
>  	if (HAS_PCH_NOP(dev))
> @@ -1262,9 +1264,8 @@ intel_parse_bios(struct drm_device *dev)
>  
>  	/* XXX Should this validation be moved to intel_opregion.c? */
>  	if (!dmi_check_system(intel_no_opregion_vbt) && dev_priv->opregion.vbt)
> -		bdb = validate_vbt((char *)dev_priv->opregion.header, OPREGION_SIZE,
> -				   (struct vbt_header *)dev_priv->opregion.vbt,
> -				   "OpRegion");
> +		bdb = validate_vbt(dev_priv->opregion.header, OPREGION_SIZE,
> +				   dev_priv->opregion.vbt, "OpRegion");
>  
>  	if (bdb == NULL) {
>  		size_t i, size;
> @@ -1277,7 +1278,7 @@ intel_parse_bios(struct drm_device *dev)
>  		for (i = 0; i + 4 < size; i++) {
>  			if (memcmp(bios + i, "$VBT", 4) == 0) {
>  				bdb = validate_vbt(bios, size,
> -						   (struct vbt_header *)(bios + i),
> +						   bios + i,
>  						   "PCI ROM");
>  				break;
>  			}
> -- 
> 2.1.4
Daniel Vetter May 12, 2015, 1:07 p.m. UTC | #2
On Tue, May 12, 2015 at 03:53:49PM +0300, Ville Syrjälä wrote:
> On Tue, May 12, 2015 at 03:41:32PM +0300, Jani Nikula wrote:
> > Make input and output of validate_vbt const, and fix the fallout. We
> > shouldn't modify the VBT, so make the compiler help us here.
> > 
> > v2: use pointer arithmetics on void* to simplify (Ville)
> > 
> > Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> 
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Both patches merged, thanks.
-Daniel

> 
> > ---
> >  drivers/gpu/drm/i915/intel_bios.c | 49 ++++++++++++++++++++-------------------
> >  1 file changed, 25 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> > index 5876e7cb132d..cbd16c01959a 100644
> > --- a/drivers/gpu/drm/i915/intel_bios.c
> > +++ b/drivers/gpu/drm/i915/intel_bios.c
> > @@ -205,7 +205,7 @@ get_lvds_fp_timing(const struct bdb_header *bdb,
> >  /* Try to find integrated panel data */
> >  static void
> >  parse_lfp_panel_data(struct drm_i915_private *dev_priv,
> > -			    struct bdb_header *bdb)
> > +		     const struct bdb_header *bdb)
> >  {
> >  	const struct bdb_lvds_options *lvds_options;
> >  	const struct bdb_lvds_lfp_data *lvds_lfp_data;
> > @@ -311,7 +311,8 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv,
> >  }
> >  
> >  static void
> > -parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
> > +parse_lfp_backlight(struct drm_i915_private *dev_priv,
> > +		    const struct bdb_header *bdb)
> >  {
> >  	const struct bdb_lfp_backlight_data *backlight_data;
> >  	const struct bdb_lfp_backlight_data_entry *entry;
> > @@ -349,7 +350,7 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
> >  /* Try to find sdvo panel data */
> >  static void
> >  parse_sdvo_panel_data(struct drm_i915_private *dev_priv,
> > -		      struct bdb_header *bdb)
> > +		      const struct bdb_header *bdb)
> >  {
> >  	const struct lvds_dvo_timing *dvo_timing;
> >  	struct drm_display_mode *panel_fixed_mode;
> > @@ -403,7 +404,7 @@ static int intel_bios_ssc_frequency(struct drm_device *dev,
> >  
> >  static void
> >  parse_general_features(struct drm_i915_private *dev_priv,
> > -		       struct bdb_header *bdb)
> > +		       const struct bdb_header *bdb)
> >  {
> >  	struct drm_device *dev = dev_priv->dev;
> >  	const struct bdb_general_features *general;
> > @@ -429,7 +430,7 @@ parse_general_features(struct drm_i915_private *dev_priv,
> >  
> >  static void
> >  parse_general_definitions(struct drm_i915_private *dev_priv,
> > -			  struct bdb_header *bdb)
> > +			  const struct bdb_header *bdb)
> >  {
> >  	const struct bdb_general_definitions *general;
> >  
> > @@ -456,7 +457,7 @@ child_device_ptr(const struct bdb_general_definitions *p_defs, int i)
> >  
> >  static void
> >  parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
> > -			  struct bdb_header *bdb)
> > +			  const struct bdb_header *bdb)
> >  {
> >  	struct sdvo_device_mapping *p_mapping;
> >  	const struct bdb_general_definitions *p_defs;
> > @@ -546,7 +547,7 @@ parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
> >  
> >  static void
> >  parse_driver_features(struct drm_i915_private *dev_priv,
> > -		       struct bdb_header *bdb)
> > +		      const struct bdb_header *bdb)
> >  {
> >  	const struct bdb_driver_features *driver;
> >  
> > @@ -572,7 +573,7 @@ parse_driver_features(struct drm_i915_private *dev_priv,
> >  }
> >  
> >  static void
> > -parse_edp(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
> > +parse_edp(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
> >  {
> >  	const struct bdb_edp *edp;
> >  	const struct edp_power_seq *edp_pps;
> > @@ -684,7 +685,7 @@ parse_edp(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
> >  }
> >  
> >  static void
> > -parse_psr(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
> > +parse_psr(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
> >  {
> >  	const struct bdb_psr *psr;
> >  	const struct psr_table *psr_table;
> > @@ -795,7 +796,7 @@ static u8 *goto_next_sequence(u8 *data, int *size)
> >  }
> >  
> >  static void
> > -parse_mipi(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
> > +parse_mipi(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
> >  {
> >  	const struct bdb_mipi_config *start;
> >  	const struct bdb_mipi_sequence *sequence;
> > @@ -946,7 +947,7 @@ err:
> >  }
> >  
> >  static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
> > -			   struct bdb_header *bdb)
> > +			   const struct bdb_header *bdb)
> >  {
> >  	union child_device_config *it, *child = NULL;
> >  	struct ddi_vbt_port_info *info = &dev_priv->vbt.ddi_port_info[port];
> > @@ -1048,7 +1049,7 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
> >  }
> >  
> >  static void parse_ddi_ports(struct drm_i915_private *dev_priv,
> > -			    struct bdb_header *bdb)
> > +			    const struct bdb_header *bdb)
> >  {
> >  	struct drm_device *dev = dev_priv->dev;
> >  	enum port port;
> > @@ -1068,7 +1069,7 @@ static void parse_ddi_ports(struct drm_i915_private *dev_priv,
> >  
> >  static void
> >  parse_device_mapping(struct drm_i915_private *dev_priv,
> > -		       struct bdb_header *bdb)
> > +		     const struct bdb_header *bdb)
> >  {
> >  	const struct bdb_general_definitions *p_defs;
> >  	const union child_device_config *p_child;
> > @@ -1198,19 +1199,20 @@ static const struct dmi_system_id intel_no_opregion_vbt[] = {
> >  	{ }
> >  };
> >  
> > -static struct bdb_header *validate_vbt(char *base, size_t size,
> > -				       struct vbt_header *vbt,
> > -				       const char *source)
> > +static const struct bdb_header *validate_vbt(const void *base, size_t size,
> > +					     const void *_vbt,
> > +					     const char *source)
> >  {
> > +	const struct vbt_header *vbt = _vbt;
> >  	size_t offset;
> > -	struct bdb_header *bdb;
> > +	const struct bdb_header *bdb;
> >  
> >  	if (vbt == NULL) {
> >  		DRM_DEBUG_DRIVER("VBT signature missing\n");
> >  		return NULL;
> >  	}
> >  
> > -	offset = (char *)vbt - base;
> > +	offset = _vbt - base;
> >  	if (offset + sizeof(struct vbt_header) > size) {
> >  		DRM_DEBUG_DRIVER("VBT header incomplete\n");
> >  		return NULL;
> > @@ -1227,7 +1229,7 @@ static struct bdb_header *validate_vbt(char *base, size_t size,
> >  		return NULL;
> >  	}
> >  
> > -	bdb = (struct bdb_header *)(base + offset);
> > +	bdb = base + offset;
> >  	if (offset + bdb->bdb_size > size) {
> >  		DRM_DEBUG_DRIVER("BDB incomplete\n");
> >  		return NULL;
> > @@ -1252,7 +1254,7 @@ intel_parse_bios(struct drm_device *dev)
> >  {
> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> >  	struct pci_dev *pdev = dev->pdev;
> > -	struct bdb_header *bdb = NULL;
> > +	const struct bdb_header *bdb = NULL;
> >  	u8 __iomem *bios = NULL;
> >  
> >  	if (HAS_PCH_NOP(dev))
> > @@ -1262,9 +1264,8 @@ intel_parse_bios(struct drm_device *dev)
> >  
> >  	/* XXX Should this validation be moved to intel_opregion.c? */
> >  	if (!dmi_check_system(intel_no_opregion_vbt) && dev_priv->opregion.vbt)
> > -		bdb = validate_vbt((char *)dev_priv->opregion.header, OPREGION_SIZE,
> > -				   (struct vbt_header *)dev_priv->opregion.vbt,
> > -				   "OpRegion");
> > +		bdb = validate_vbt(dev_priv->opregion.header, OPREGION_SIZE,
> > +				   dev_priv->opregion.vbt, "OpRegion");
> >  
> >  	if (bdb == NULL) {
> >  		size_t i, size;
> > @@ -1277,7 +1278,7 @@ intel_parse_bios(struct drm_device *dev)
> >  		for (i = 0; i + 4 < size; i++) {
> >  			if (memcmp(bios + i, "$VBT", 4) == 0) {
> >  				bdb = validate_vbt(bios, size,
> > -						   (struct vbt_header *)(bios + i),
> > +						   bios + i,
> >  						   "PCI ROM");
> >  				break;
> >  			}
> > -- 
> > 2.1.4
> 
> -- 
> Ville Syrjälä
> Intel OTC
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

Patch
diff mbox

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 5876e7cb132d..cbd16c01959a 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -205,7 +205,7 @@  get_lvds_fp_timing(const struct bdb_header *bdb,
 /* Try to find integrated panel data */
 static void
 parse_lfp_panel_data(struct drm_i915_private *dev_priv,
-			    struct bdb_header *bdb)
+		     const struct bdb_header *bdb)
 {
 	const struct bdb_lvds_options *lvds_options;
 	const struct bdb_lvds_lfp_data *lvds_lfp_data;
@@ -311,7 +311,8 @@  parse_lfp_panel_data(struct drm_i915_private *dev_priv,
 }
 
 static void
-parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
+parse_lfp_backlight(struct drm_i915_private *dev_priv,
+		    const struct bdb_header *bdb)
 {
 	const struct bdb_lfp_backlight_data *backlight_data;
 	const struct bdb_lfp_backlight_data_entry *entry;
@@ -349,7 +350,7 @@  parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 /* Try to find sdvo panel data */
 static void
 parse_sdvo_panel_data(struct drm_i915_private *dev_priv,
-		      struct bdb_header *bdb)
+		      const struct bdb_header *bdb)
 {
 	const struct lvds_dvo_timing *dvo_timing;
 	struct drm_display_mode *panel_fixed_mode;
@@ -403,7 +404,7 @@  static int intel_bios_ssc_frequency(struct drm_device *dev,
 
 static void
 parse_general_features(struct drm_i915_private *dev_priv,
-		       struct bdb_header *bdb)
+		       const struct bdb_header *bdb)
 {
 	struct drm_device *dev = dev_priv->dev;
 	const struct bdb_general_features *general;
@@ -429,7 +430,7 @@  parse_general_features(struct drm_i915_private *dev_priv,
 
 static void
 parse_general_definitions(struct drm_i915_private *dev_priv,
-			  struct bdb_header *bdb)
+			  const struct bdb_header *bdb)
 {
 	const struct bdb_general_definitions *general;
 
@@ -456,7 +457,7 @@  child_device_ptr(const struct bdb_general_definitions *p_defs, int i)
 
 static void
 parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
-			  struct bdb_header *bdb)
+			  const struct bdb_header *bdb)
 {
 	struct sdvo_device_mapping *p_mapping;
 	const struct bdb_general_definitions *p_defs;
@@ -546,7 +547,7 @@  parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
 
 static void
 parse_driver_features(struct drm_i915_private *dev_priv,
-		       struct bdb_header *bdb)
+		      const struct bdb_header *bdb)
 {
 	const struct bdb_driver_features *driver;
 
@@ -572,7 +573,7 @@  parse_driver_features(struct drm_i915_private *dev_priv,
 }
 
 static void
-parse_edp(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
+parse_edp(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
 {
 	const struct bdb_edp *edp;
 	const struct edp_power_seq *edp_pps;
@@ -684,7 +685,7 @@  parse_edp(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 }
 
 static void
-parse_psr(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
+parse_psr(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
 {
 	const struct bdb_psr *psr;
 	const struct psr_table *psr_table;
@@ -795,7 +796,7 @@  static u8 *goto_next_sequence(u8 *data, int *size)
 }
 
 static void
-parse_mipi(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
+parse_mipi(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
 {
 	const struct bdb_mipi_config *start;
 	const struct bdb_mipi_sequence *sequence;
@@ -946,7 +947,7 @@  err:
 }
 
 static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
-			   struct bdb_header *bdb)
+			   const struct bdb_header *bdb)
 {
 	union child_device_config *it, *child = NULL;
 	struct ddi_vbt_port_info *info = &dev_priv->vbt.ddi_port_info[port];
@@ -1048,7 +1049,7 @@  static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
 }
 
 static void parse_ddi_ports(struct drm_i915_private *dev_priv,
-			    struct bdb_header *bdb)
+			    const struct bdb_header *bdb)
 {
 	struct drm_device *dev = dev_priv->dev;
 	enum port port;
@@ -1068,7 +1069,7 @@  static void parse_ddi_ports(struct drm_i915_private *dev_priv,
 
 static void
 parse_device_mapping(struct drm_i915_private *dev_priv,
-		       struct bdb_header *bdb)
+		     const struct bdb_header *bdb)
 {
 	const struct bdb_general_definitions *p_defs;
 	const union child_device_config *p_child;
@@ -1198,19 +1199,20 @@  static const struct dmi_system_id intel_no_opregion_vbt[] = {
 	{ }
 };
 
-static struct bdb_header *validate_vbt(char *base, size_t size,
-				       struct vbt_header *vbt,
-				       const char *source)
+static const struct bdb_header *validate_vbt(const void *base, size_t size,
+					     const void *_vbt,
+					     const char *source)
 {
+	const struct vbt_header *vbt = _vbt;
 	size_t offset;
-	struct bdb_header *bdb;
+	const struct bdb_header *bdb;
 
 	if (vbt == NULL) {
 		DRM_DEBUG_DRIVER("VBT signature missing\n");
 		return NULL;
 	}
 
-	offset = (char *)vbt - base;
+	offset = _vbt - base;
 	if (offset + sizeof(struct vbt_header) > size) {
 		DRM_DEBUG_DRIVER("VBT header incomplete\n");
 		return NULL;
@@ -1227,7 +1229,7 @@  static struct bdb_header *validate_vbt(char *base, size_t size,
 		return NULL;
 	}
 
-	bdb = (struct bdb_header *)(base + offset);
+	bdb = base + offset;
 	if (offset + bdb->bdb_size > size) {
 		DRM_DEBUG_DRIVER("BDB incomplete\n");
 		return NULL;
@@ -1252,7 +1254,7 @@  intel_parse_bios(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct pci_dev *pdev = dev->pdev;
-	struct bdb_header *bdb = NULL;
+	const struct bdb_header *bdb = NULL;
 	u8 __iomem *bios = NULL;
 
 	if (HAS_PCH_NOP(dev))
@@ -1262,9 +1264,8 @@  intel_parse_bios(struct drm_device *dev)
 
 	/* XXX Should this validation be moved to intel_opregion.c? */
 	if (!dmi_check_system(intel_no_opregion_vbt) && dev_priv->opregion.vbt)
-		bdb = validate_vbt((char *)dev_priv->opregion.header, OPREGION_SIZE,
-				   (struct vbt_header *)dev_priv->opregion.vbt,
-				   "OpRegion");
+		bdb = validate_vbt(dev_priv->opregion.header, OPREGION_SIZE,
+				   dev_priv->opregion.vbt, "OpRegion");
 
 	if (bdb == NULL) {
 		size_t i, size;
@@ -1277,7 +1278,7 @@  intel_parse_bios(struct drm_device *dev)
 		for (i = 0; i + 4 < size; i++) {
 			if (memcmp(bios + i, "$VBT", 4) == 0) {
 				bdb = validate_vbt(bios, size,
-						   (struct vbt_header *)(bios + i),
+						   bios + i,
 						   "PCI ROM");
 				break;
 			}