Re: [PATCH 1/2] drm/i915: constify find_section in VBT parsing

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Apr 15, 2015 at 03:18:28PM +0300, Jani Nikula wrote:
> Make input and output of find_section const, and fix the fallout. We
> shouldn't modify the VBT, so make the compiler help us here.
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_bios.c | 60 ++++++++++++++++++++-------------------
>  1 file changed, 31 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index c08368c03dad..4e3f3f427178 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -36,10 +36,11 @@
>  
>  static int panel_type;
>  
> -static void *
> -find_section(struct bdb_header *bdb, int section_id)
> +static const void *
> +find_section(const void *_bdb, int section_id)
>  {
> -	u8 *base = (u8 *)bdb;
> +	const struct bdb_header *bdb = _bdb;
> +	const u8 *base = _bdb;
>  	int index = 0;
>  	u16 total, current_size;
>  	u8 current_id;
> @@ -53,7 +54,7 @@ find_section(struct bdb_header *bdb, int section_id)
>  		current_id = *(base + index);
>  		index++;
>  
> -		current_size = *((u16 *)(base + index));
> +		current_size = *((const u16 *)(base + index));
>  		index += 2;
>  
>  		if (index + current_size > total)
> @@ -69,7 +70,7 @@ find_section(struct bdb_header *bdb, int section_id)
>  }
>  
>  static u16
> -get_blocksize(void *p)
> +get_blocksize(const void *p)
>  {
>  	u16 *block_ptr, block_size;
>  
> @@ -350,7 +351,7 @@ static void
>  parse_sdvo_panel_data(struct drm_i915_private *dev_priv,
>  		      struct bdb_header *bdb)
>  {
> -	struct lvds_dvo_timing *dvo_timing;
> +	const struct lvds_dvo_timing *dvo_timing;
>  	struct drm_display_mode *panel_fixed_mode;
>  	int index;
>  
> @@ -361,7 +362,7 @@ parse_sdvo_panel_data(struct drm_i915_private *dev_priv,
>  	}
>  
>  	if (index == -1) {
> -		struct bdb_sdvo_lvds_options *sdvo_lvds_options;
> +		const struct bdb_sdvo_lvds_options *sdvo_lvds_options;
>  
>  		sdvo_lvds_options = find_section(bdb, BDB_SDVO_LVDS_OPTIONS);
>  		if (!sdvo_lvds_options)
> @@ -405,7 +406,7 @@ parse_general_features(struct drm_i915_private *dev_priv,
>  		       struct bdb_header *bdb)
>  {
>  	struct drm_device *dev = dev_priv->dev;
> -	struct bdb_general_features *general;
> +	const struct bdb_general_features *general;
>  
>  	general = find_section(bdb, BDB_GENERAL_FEATURES);
>  	if (general) {
> @@ -430,7 +431,7 @@ static void
>  parse_general_definitions(struct drm_i915_private *dev_priv,
>  			  struct bdb_header *bdb)
>  {
> -	struct bdb_general_definitions *general;
> +	const struct bdb_general_definitions *general;
>  
>  	general = find_section(bdb, BDB_GENERAL_DEFINITIONS);
>  	if (general) {
> @@ -447,10 +448,10 @@ parse_general_definitions(struct drm_i915_private *dev_priv,
>  	}
>  }
>  
> -static union child_device_config *
> -child_device_ptr(struct bdb_general_definitions *p_defs, int i)
> +static const union child_device_config *
> +child_device_ptr(const struct bdb_general_definitions *p_defs, int i)
>  {
> -	return (void *) &p_defs->devices[i * p_defs->child_dev_size];
> +	return (const void *) &p_defs->devices[i * p_defs->child_dev_size];
>  }
>  
>  static void
> @@ -458,8 +459,8 @@ parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
>  			  struct bdb_header *bdb)
>  {
>  	struct sdvo_device_mapping *p_mapping;
> -	struct bdb_general_definitions *p_defs;
> -	union child_device_config *p_child;
> +	const struct bdb_general_definitions *p_defs;
> +	const union child_device_config *p_child;
>  	int i, child_device_num, count;
>  	u16	block_size;
>  
> @@ -547,7 +548,7 @@ static void
>  parse_driver_features(struct drm_i915_private *dev_priv,
>  		       struct bdb_header *bdb)
>  {
> -	struct bdb_driver_features *driver;
> +	const struct bdb_driver_features *driver;
>  
>  	driver = find_section(bdb, BDB_DRIVER_FEATURES);
>  	if (!driver)
> @@ -573,9 +574,9 @@ parse_driver_features(struct drm_i915_private *dev_priv,
>  static void
>  parse_edp(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
>  {
> -	struct bdb_edp *edp;
> -	struct edp_power_seq *edp_pps;
> -	struct edp_link_params *edp_link_params;
> +	const struct bdb_edp *edp;
> +	const struct edp_power_seq *edp_pps;
> +	const struct edp_link_params *edp_link_params;
>  
>  	edp = find_section(bdb, BDB_EDP);
>  	if (!edp) {
> @@ -680,8 +681,8 @@ 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)
>  {
> -	struct bdb_psr *psr;
> -	struct psr_table *psr_table;
> +	const struct bdb_psr *psr;
> +	const struct psr_table *psr_table;
>  
>  	psr = find_section(bdb, BDB_PSR);
>  	if (!psr) {
> @@ -791,11 +792,12 @@ static u8 *goto_next_sequence(u8 *data, int *size)
>  static void
>  parse_mipi(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
>  {
> -	struct bdb_mipi_config *start;
> -	struct bdb_mipi_sequence *sequence;
> -	struct mipi_config *config;
> -	struct mipi_pps_data *pps;
> -	u8 *data, *seq_data;
> +	const struct bdb_mipi_config *start;
> +	const struct bdb_mipi_sequence *sequence;
> +	const struct mipi_config *config;
> +	const struct mipi_pps_data *pps;
> +	u8 *data;

It would seem this guy could be constified as well, with a bit of extra
effort that is.

But the patch as is looks reasonable so:
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> +	const u8 *seq_data;
>  	int i, panel_id, seq_size;
>  	u16 block_size;
>  
> @@ -1063,8 +1065,9 @@ static void
>  parse_device_mapping(struct drm_i915_private *dev_priv,
>  		       struct bdb_header *bdb)
>  {
> -	struct bdb_general_definitions *p_defs;
> -	union child_device_config *p_child, *child_dev_ptr;
> +	const struct bdb_general_definitions *p_defs;
> +	const union child_device_config *p_child;
> +	union child_device_config *child_dev_ptr;
>  	int i, child_device_num, count;
>  	u16	block_size;
>  
> @@ -1121,8 +1124,7 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
>  
>  		child_dev_ptr = dev_priv->vbt.child_dev + count;
>  		count++;
> -		memcpy((void *)child_dev_ptr, (void *)p_child,
> -					sizeof(*p_child));
> +		memcpy(child_dev_ptr, p_child, sizeof(*p_child));
>  	}
>  	return;
>  }
> -- 
> 2.1.4
> 
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-- 
Ville Syrjälä
Intel OTC
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