Seems reasonable to me. I would say we should set it in Vulkan too except
that the only way you can get a buffer size of 0 is invalid usage so meh.
Reviewed-by: Jason Ekstrand <ja...@jlekstrand.net>
On Sun, Oct 8, 2017 at 7:47 PM, Kenneth Graunke <kenn...@whitecape.org>
wrote:
> According to the Broadwell VERTEX_BUFFER_STATE documentation,
>
> "VERTEX_BUFFER_STATE.Null Vertex Buffer must be set when the
> VERTEX_BUFFER_STATE.Buffer Size is 0x0.
> ---
> src/intel/blorp/blorp_genX_exec.h | 2 ++
> src/mesa/drivers/dri/i965/genX_state_upload.c | 5 ++++-
> 2 files changed, 6 insertions(+), 1 deletion(-)
>
> I'm not sure why anyone would ever /use/ a vertex buffer of size 0,
> but...easy enough to follow the required programming...
>
> diff --git a/src/intel/blorp/blorp_genX_exec.h
> b/src/intel/blorp/blorp_genX_exec.h
> index 53892620986..e3fb6d9ae5f 100644
> --- a/src/intel/blorp/blorp_genX_exec.h
> +++ b/src/intel/blorp/blorp_genX_exec.h
> @@ -280,6 +280,7 @@ blorp_emit_vertex_buffers(struct blorp_batch *batch,
> vb[0].BufferAccessType = VERTEXDATA;
> vb[0].EndAddress = vb[0].BufferStartingAddress;
> vb[0].EndAddress.offset += size - 1;
> + vb[0].NullVertexBuffer = size == 0;
> #elif GEN_GEN == 4
> vb[0].BufferAccessType = VERTEXDATA;
> vb[0].MaxIndex = 2;
> @@ -301,6 +302,7 @@ blorp_emit_vertex_buffers(struct blorp_batch *batch,
> vb[1].BufferAccessType = INSTANCEDATA;
> vb[1].EndAddress = vb[1].BufferStartingAddress;
> vb[1].EndAddress.offset += size - 1;
> + vb[1].NullVertexBuffer = size == 0;
> #elif GEN_GEN == 4
> vb[1].BufferAccessType = INSTANCEDATA;
> vb[1].MaxIndex = 0;
> diff --git a/src/mesa/drivers/dri/i965/genX_state_upload.c
> b/src/mesa/drivers/dri/i965/genX_state_upload.c
> index ecf5a9ae68d..7fe1f12d5ed 100644
> --- a/src/mesa/drivers/dri/i965/genX_state_upload.c
> +++ b/src/mesa/drivers/dri/i965/genX_state_upload.c
> @@ -317,12 +317,14 @@ genX(emit_vertex_buffer_state)(struct brw_context
> *brw,
> unsigned stride,
> unsigned step_rate)
> {
> + UNUSED unsigned size = end_offset - start_offset;
> +
> struct GENX(VERTEX_BUFFER_STATE) buf_state = {
> .VertexBufferIndex = buffer_nr,
> .BufferPitch = stride,
> .BufferStartingAddress = ro_bo(bo, start_offset),
> #if GEN_GEN >= 8
> - .BufferSize = end_offset - start_offset,
> + .BufferSize = size,
> #endif
>
> #if GEN_GEN >= 7
> @@ -334,6 +336,7 @@ genX(emit_vertex_buffer_state)(struct brw_context
> *brw,
> .InstanceDataStepRate = step_rate,
> #if GEN_GEN >= 5
> .EndAddress = ro_bo(bo, end_offset - 1),
> + .NullVertexBuffer = size == 0,
> #endif
> #endif
>
> --
> 2.14.2
>
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> mesa-dev@lists.freedesktop.org
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>
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