[Mesa-dev] [PATCH 6/6] intel/isl: Improve the documentation on get_default_aux_state

[Chad Versace]

On Wed 24 Jan 2018, Jason Ekstrand wrote:
> Cc: Chad Versace <chadversary at chromium.org>
> ---
>  src/intel/isl/isl.h | 24 ++++++++++++++++++++----
>  1 file changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/src/intel/isl/isl.h b/src/intel/isl/isl.h
> index e3acb0e..cf53b5a 100644
> --- a/src/intel/isl/isl.h
> +++ b/src/intel/isl/isl.h
> @@ -1565,10 +1565,25 @@ isl_drm_modifier_has_aux(uint64_t modifier)
>  
>  /** Returns the default isl_aux_state for the given modifier.
>   *
> - * All modified images are required to be kept out of the AUX_INVALID state
> - * but they may or may not actually be compressed and may or may not have
> - * clear color.  This function returns the worst case aux_state that we need
                                              ^^^^^^^^^^^^^^^^^^^^

I was always uncomfortable with the phrase "worst case aux state".
I like the new, precise documentation much better.

Reviewed-by: Chad Versace <chadversary at chromium.org>

/eom

> - * to assume when getting a surface from another process or API.
> + * If we have a modifier which supports compression, then the auxiliary data
> + * could be in state other than ISL_AUX_STATE_AUX_INVALID.  In particular, it
> + * can be in any of the following:
> + *
> + *  - ISL_AUX_STATE_CLEAR
> + *  - ISL_AUX_STATE_PARTIAL_CLEAR
> + *  - ISL_AUX_STATE_COMPRESSED_CLEAR
> + *  - ISL_AUX_STATE_COMPRESSED_NO_CLEAR
> + *  - ISL_AUX_STATE_RESOLVED
> + *  - ISL_AUX_STATE_PASS_THROUGH
> + *
> + * If the modifier does not support fast-clears, then we are guaranteed
> + * that the surface is at least partially resolved and the first three not
> + * possible.  We return ISL_AUX_STATE_COMPRESSED_CLEAR if the modifier
> + * supports fast clears and ISL_AUX_STATE_COMPRESSED_NO_CLEAR if it does not
> + * because they are the least common denominator of the set of possible aux
> + * states and will yield a valid interpretation of the aux data.
> + *
> + * For modifiers with no aux support, ISL_AUX_STATE_AUX_INVALID is returned.
>   */
>  static inline enum isl_aux_state
>  isl_drm_modifier_get_default_aux_state(uint64_t modifier)
> @@ -1579,6 +1594,7 @@ isl_drm_modifier_get_default_aux_state(uint64_t modifier)
>     if (!mod_info || mod_info->aux_usage == ISL_AUX_USAGE_NONE)
>        return ISL_AUX_STATE_AUX_INVALID;
>  
> +   assert(mod_info->aux_usage == ISL_AUX_USAGE_CCS_E);
>     return mod_info->supports_clear_color ? ISL_AUX_STATE_COMPRESSED_CLEAR :
>                                             ISL_AUX_STATE_COMPRESSED_NO_CLEAR;
>  }
> -- 
> 2.5.0.400.gff86faf
> 
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