[Intel-gfx] [PATCH 3/3] drm/i915: Add code comment on assumption of pipe==transcoder

[Ville Syrjälä]

On Mon, Nov 19, 2018 at 04:41:09PM +0200, Imre Deak wrote:
> Add a comment to the pipe and transcoder enum definitions about our
> assumption in the code that pipe==transcoder for PIPE_A-C /
> TRANSCODER_A-C. This means we have to keep the values for these
> pipe/transcoder enums fixed.
> 
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> Cc: Mika Kahola <mika.kahola at intel.com>
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.h b/drivers/gpu/drm/i915/intel_display.h
> index 43eb4ebbcc35..cbb5d79d6a4c 100644
> --- a/drivers/gpu/drm/i915/intel_display.h
> +++ b/drivers/gpu/drm/i915/intel_display.h
> @@ -43,6 +43,10 @@ enum i915_gpio {
>  	GPIOM,
>  };
>  
> +/*
> + * Keep the PIPE_A-C values fixed, we assume that pipe==transcoder for
> + * these pipes.
> + */

I suspect the A-C part is going to bitrot. Also I'm sure we
make more assupmtions about these values (PIPE_A == 0,
PIPE_N+1 == n+1, etc.). We should probably try to spell it
all out here.

>  enum pipe {
>  	INVALID_PIPE = -1,
>  
> @@ -56,6 +60,10 @@ enum pipe {
>  
>  #define pipe_name(p) ((p) + 'A')
>  
> +/*
> + * Keep the TRANSCODER_A-C values fixed, we assume that pipe==transcoder for
> + * these transcoders.
> + */

Same issue with the A-C part perhaps.

>  enum transcoder {
>  	TRANSCODER_A = 0,
>  	TRANSCODER_B,
> -- 
> 2.13.2

-- 
Ville Syrjälä
Intel