[Mesa-dev] [PATCH] i965: Advertise 8 bits subpixel precision for viewport bounds on gen6+

[Lionel Landwerlin]

Hey Danylo,

Thanks for this patch.
I'm not really an expert here but my understanding is that it should 
reflect the number of bits in fixed point precision.
We use 32bits floats in the packets sent to the hardware.
Quoting the spec :

"If the implementation truely has floating point viewport bounds, it may 
report a sufficiently high value to indicate this. "

Maybe we should use something a bit bigger than 8?

Cheers,

-
Lionel

On 18/06/18 13:50, Danylo Piliaiev wrote:
> We use floating-points for viewport bounds so VIEWPORT_SUBPIXEL_BITS
> should reflect this.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105975
>
> Signed-off-by: Danylo Piliaiev <danylo.piliaiev at globallogic.com>
> ---
>   src/mesa/drivers/dri/i965/brw_context.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
> index 9ced230..eacf326 100644
> --- a/src/mesa/drivers/dri/i965/brw_context.c
> +++ b/src/mesa/drivers/dri/i965/brw_context.c
> @@ -688,7 +688,7 @@ brw_initialize_context_constants(struct brw_context *brw)
>      /* ARB_viewport_array, OES_viewport_array */
>      if (devinfo->gen >= 6) {
>         ctx->Const.MaxViewports = GEN6_NUM_VIEWPORTS;
> -      ctx->Const.ViewportSubpixelBits = 0;
> +      ctx->Const.ViewportSubpixelBits = 8;
>   
>         /* Cast to float before negating because MaxViewportWidth is unsigned.
>          */


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