Re: [PATCH] Big endian support for RV730 (Gallium r600g)

[ Moving to the mesa-dev list ]

On Fre, 2011-04-15 at 18:20 +0200, Cédric Cano wrote:

Here you are a patch that adds big endian support for rv730 in r600 gallium driver.

I used the mesa-demos to test the driver status on big endian platform. Except with demos using accumulation buffer, the rendering is the same as on Intel platform. Albeit there are still some artefacts with some demos.

I manage to fix accumulation buffer demos but then, glReadPixels demos won't work. I still can figure out (like with r600c) what and when I must enable swap. It will depends on object's domains. That's what I tried to do in r600_cb and r600_create_sampler_view.

That's probably because it hasn't been fully thought through yet how to deal with big endian CPUs vs. little endian GPUs in Gallium. When this was discussed previously, the basic rule decided was that all data passed across the Gallium driver interface was supposed to be little endian. That should probably be feasible in general for at least 'standard' pixel formats, but I'm afraid it doesn't really work for vertex data[0], which could be fed from the application (which will use CPU native byte order) to the GPU more or less directly.

Maybe byte order should be handled explicitly by the Gallium format definitions, and then it would be up to the state tracker to use the appropriate byte order formats. José, have you had any further thoughts on this?

[0] Though there might also be ambiguities e.g. with multi-byte component pixel formats: Does the little endian rule apply to the pixel value as a whole, or only for each component?

@@ -266,11 +268,31 @@ void r600_upload_const_buffer(struct r600_pipe_context *rctx, struct r600_resour uint8_t *ptr = (*rbuffer)->r.b.user_ptr; unsigned size = (*rbuffer)->r.b.b.b.width0; boolean flushed; +#ifdef PIPE_ARCH_BIG_ENDIAN

•           int i;
  

•           uint32_t *tmpPtr;
  

•           *rbuffer = NULL;
  

•           tmpPtr = (uint32_t *)malloc(size);
  

•           /* big endian swap */
  

•           if(tmpPtr == NULL) {
  

•                   return;
  

•           }
  

•           for(i = 0; i < size / 4; i++) {
  

•                   tmpPtr[i] = bswap_32(*((uint32_t *)ptr + i));
  

•           }
  

•           u_upload_data(rctx->vbuf_mgr->uploader, 0, size, tmpPtr, const_offset,
  

•                         (struct pipe_resource**)rbuffer, &flushed);
  

Might be better to add a helper like u_upload_data_to_le32().