src/gallium/drivers/nouveau/nvc0/nvc0_context.c

   1 /*
   2  * Copyright 2010 Christoph Bumiller
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included in
  12  * all copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  17  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  18  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  19  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  20  * OTHER DEALINGS IN THE SOFTWARE.
  21  */
  22
  23 #include "pipe/p_defines.h"
  24 #include "util/u_framebuffer.h"
  25
  26 #include "nvc0/nvc0_context.h"
  27 #include "nvc0/nvc0_screen.h"
  28 #include "nvc0/nvc0_resource.h"
  29
  30 static void
  31 nvc0_flush(struct pipe_context *pipe,
  32            struct pipe_fence_handle **fence,
  33            unsigned flags)
  34 {
  35    struct nvc0_context *nvc0 = nvc0_context(pipe);
  36    struct nouveau_screen *screen = &nvc0->screen->base;
  37
  38    if (fence)
  39       nouveau_fence_ref(screen->fence.current, (struct nouveau_fence **)fence);
  40
  41    PUSH_KICK(nvc0->base.pushbuf); /* fencing handled in kick_notify */
  42
  43    nouveau_context_update_frame_stats(&nvc0->base);
  44 }
  45
  46 static void
  47 nvc0_texture_barrier(struct pipe_context *pipe)
  48 {
  49    struct nouveau_pushbuf *push = nvc0_context(pipe)->base.pushbuf;
  50
  51    IMMED_NVC0(push, NVC0_3D(SERIALIZE), 0);
  52    IMMED_NVC0(push, NVC0_3D(TEX_CACHE_CTL), 0);
  53 }
  54
  55 static void
  56 nvc0_memory_barrier(struct pipe_context *pipe, unsigned flags)
  57 {
  58    struct nvc0_context *nvc0 = nvc0_context(pipe);
  59    struct nouveau_pushbuf *push = nvc0->base.pushbuf;
  60    int i, s;
  61
  62    if (flags & PIPE_BARRIER_MAPPED_BUFFER) {
  63       for (i = 0; i < nvc0->num_vtxbufs; ++i) {
  64          if (!nvc0->vtxbuf[i].buffer)
  65             continue;
  66          if (nvc0->vtxbuf[i].buffer->flags & PIPE_RESOURCE_FLAG_MAP_PERSISTENT)
  67             nvc0->base.vbo_dirty = true;
  68       }
  69
  70       if (nvc0->idxbuf.buffer &&
  71           nvc0->idxbuf.buffer->flags & PIPE_RESOURCE_FLAG_MAP_PERSISTENT)
  72          nvc0->base.vbo_dirty = true;
  73
  74       for (s = 0; s < 5 && !nvc0->cb_dirty; ++s) {
  75          uint32_t valid = nvc0->constbuf_valid[s];
  76
  77          while (valid && !nvc0->cb_dirty) {
  78             const unsigned i = ffs(valid) - 1;
  79             struct pipe_resource *res;
  80
  81             valid &= ~(1 << i);
  82             if (nvc0->constbuf[s][i].user)
  83                continue;
  84
  85             res = nvc0->constbuf[s][i].u.buf;
  86             if (!res)
  87                continue;
  88
  89             if (res->flags & PIPE_RESOURCE_FLAG_MAP_PERSISTENT)
  90                nvc0->cb_dirty = true;
  91          }
  92       }
  93    } else {
  94       /* Pretty much any writing by shaders needs a serialize after
  95        * it. Especially when moving between 3d and compute pipelines, but even
  96        * without that.
  97        */
  98       IMMED_NVC0(push, NVC0_3D(SERIALIZE), 0);
  99    }
 100
 101    /* If we're going to texture from a buffer/image written by a shader, we
 102     * must flush the texture cache.
 103     */
 104    if (flags & PIPE_BARRIER_TEXTURE)
 105       IMMED_NVC0(push, NVC0_3D(TEX_CACHE_CTL), 0);
 106
 107    if (flags & PIPE_BARRIER_CONSTANT_BUFFER)
 108       nvc0->cb_dirty = true;
 109    if (flags & (PIPE_BARRIER_VERTEX_BUFFER | PIPE_BARRIER_INDEX_BUFFER))
 110       nvc0->base.vbo_dirty = true;
 111 }
 112
 113 static void
 114 nvc0_emit_string_marker(struct pipe_context *pipe, const char *str, int len)
 115 {
 116    struct nouveau_pushbuf *push = nvc0_context(pipe)->base.pushbuf;
 117    int string_words = len / 4;
 118    int data_words;
 119
 120    if (len <= 0)
 121       return;
 122    string_words = MIN2(string_words, NV04_PFIFO_MAX_PACKET_LEN);
 123    if (string_words == NV04_PFIFO_MAX_PACKET_LEN)
 124       data_words = string_words;
 125    else
 126       data_words = string_words + !!(len & 3);
 127    BEGIN_NIC0(push, SUBC_3D(NV04_GRAPH_NOP), data_words);
 128    if (string_words)
 129       PUSH_DATAp(push, str, string_words);
 130    if (string_words != data_words) {
 131       int data = 0;
 132       memcpy(&data, &str[string_words * 4], len & 3);
 133       PUSH_DATA (push, data);
 134    }
 135 }
 136
 137 static void
 138 nvc0_context_unreference_resources(struct nvc0_context *nvc0)
 139 {
 140    unsigned s, i;
 141
 142    nouveau_bufctx_del(&nvc0->bufctx_3d);
 143    nouveau_bufctx_del(&nvc0->bufctx);
 144    nouveau_bufctx_del(&nvc0->bufctx_cp);
 145
 146    util_unreference_framebuffer_state(&nvc0->framebuffer);
 147
 148    for (i = 0; i < nvc0->num_vtxbufs; ++i)
 149       pipe_resource_reference(&nvc0->vtxbuf[i].buffer, NULL);
 150
 151    pipe_resource_reference(&nvc0->idxbuf.buffer, NULL);
 152
 153    for (s = 0; s < 6; ++s) {
 154       for (i = 0; i < nvc0->num_textures[s]; ++i)
 155          pipe_sampler_view_reference(&nvc0->textures[s][i], NULL);
 156
 157       for (i = 0; i < NVC0_MAX_PIPE_CONSTBUFS; ++i)
 158          if (!nvc0->constbuf[s][i].user)
 159             pipe_resource_reference(&nvc0->constbuf[s][i].u.buf, NULL);
 160
 161       for (i = 0; i < NVC0_MAX_BUFFERS; ++i)
 162          pipe_resource_reference(&nvc0->buffers[s][i].buffer, NULL);
 163
 164       for (i = 0; i < NVC0_MAX_IMAGES; ++i)
 165          pipe_resource_reference(&nvc0->images[s][i].resource, NULL);
 166    }
 167
 168    for (s = 0; s < 2; ++s) {
 169       for (i = 0; i < NVC0_MAX_SURFACE_SLOTS; ++i)
 170          pipe_surface_reference(&nvc0->surfaces[s][i], NULL);
 171    }
 172
 173    for (i = 0; i < nvc0->num_tfbbufs; ++i)
 174       pipe_so_target_reference(&nvc0->tfbbuf[i], NULL);
 175
 176    for (i = 0; i < nvc0->global_residents.size / sizeof(struct pipe_resource *);
 177         ++i) {
 178       struct pipe_resource **res = util_dynarray_element(
 179          &nvc0->global_residents, struct pipe_resource *, i);
 180       pipe_resource_reference(res, NULL);
 181    }
 182    util_dynarray_fini(&nvc0->global_residents);
 183
 184    if (nvc0->tcp_empty)
 185       nvc0->base.pipe.delete_tcs_state(&nvc0->base.pipe, nvc0->tcp_empty);
 186 }
 187
 188 static void
 189 nvc0_destroy(struct pipe_context *pipe)
 190 {
 191    struct nvc0_context *nvc0 = nvc0_context(pipe);
 192
 193    if (nvc0->screen->cur_ctx == nvc0) {
 194       nvc0->screen->cur_ctx = NULL;
 195       nvc0->screen->save_state = nvc0->state;
 196       nvc0->screen->save_state.tfb = NULL;
 197    }
 198
 199    /* Unset bufctx, we don't want to revalidate any resources after the flush.
 200     * Other contexts will always set their bufctx again on action calls.
 201     */
 202    nouveau_pushbuf_bufctx(nvc0->base.pushbuf, NULL);
 203    nouveau_pushbuf_kick(nvc0->base.pushbuf, nvc0->base.pushbuf->channel);
 204
 205    nvc0_context_unreference_resources(nvc0);
 206    nvc0_blitctx_destroy(nvc0);
 207
 208    nouveau_context_destroy(&nvc0->base);
 209 }
 210
 211 void
 212 nvc0_default_kick_notify(struct nouveau_pushbuf *push)
 213 {
 214    struct nvc0_screen *screen = push->user_priv;
 215
 216    if (screen) {
 217       nouveau_fence_next(&screen->base);
 218       nouveau_fence_update(&screen->base, true);
 219       if (screen->cur_ctx)
 220          screen->cur_ctx->state.flushed = true;
 221       NOUVEAU_DRV_STAT(&screen->base, pushbuf_count, 1);
 222    }
 223 }
 224
 225 static int
 226 nvc0_invalidate_resource_storage(struct nouveau_context *ctx,
 227                                  struct pipe_resource *res,
 228                                  int ref)
 229 {
 230    struct nvc0_context *nvc0 = nvc0_context(&ctx->pipe);
 231    unsigned s, i;
 232
 233    if (res->bind & PIPE_BIND_RENDER_TARGET) {
 234       for (i = 0; i < nvc0->framebuffer.nr_cbufs; ++i) {
 235          if (nvc0->framebuffer.cbufs[i] &&
 236              nvc0->framebuffer.cbufs[i]->texture == res) {
 237             nvc0->dirty_3d |= NVC0_NEW_3D_FRAMEBUFFER;
 238             nouveau_bufctx_reset(nvc0->bufctx_3d, NVC0_BIND_3D_FB);
 239             if (!--ref)
 240                return ref;
 241          }
 242       }
 243    }
 244    if (res->bind & PIPE_BIND_DEPTH_STENCIL) {
 245       if (nvc0->framebuffer.zsbuf &&
 246           nvc0->framebuffer.zsbuf->texture == res) {
 247          nvc0->dirty_3d |= NVC0_NEW_3D_FRAMEBUFFER;
 248          nouveau_bufctx_reset(nvc0->bufctx_3d, NVC0_BIND_3D_FB);
 249          if (!--ref)
 250             return ref;
 251       }
 252    }
 253
 254    if (res->target == PIPE_BUFFER) {
 255       for (i = 0; i < nvc0->num_vtxbufs; ++i) {
 256          if (nvc0->vtxbuf[i].buffer == res) {
 257             nvc0->dirty_3d |= NVC0_NEW_3D_ARRAYS;
 258             nouveau_bufctx_reset(nvc0->bufctx_3d, NVC0_BIND_3D_VTX);
 259             if (!--ref)
 260                return ref;
 261          }
 262       }
 263
 264       if (nvc0->idxbuf.buffer == res) {
 265          nvc0->dirty_3d |= NVC0_NEW_3D_IDXBUF;
 266          nouveau_bufctx_reset(nvc0->bufctx_3d, NVC0_BIND_3D_IDX);
 267          if (!--ref)
 268             return ref;
 269       }
 270
 271       for (s = 0; s < 6; ++s) {
 272          for (i = 0; i < nvc0->num_textures[s]; ++i) {
 273             if (nvc0->textures[s][i] &&
 274                 nvc0->textures[s][i]->texture == res) {
 275                nvc0->textures_dirty[s] |= 1 << i;
 276                if (unlikely(s == 5)) {
 277                   nvc0->dirty_cp |= NVC0_NEW_CP_TEXTURES;
 278                   nouveau_bufctx_reset(nvc0->bufctx_cp, NVC0_BIND_CP_TEX(i));
 279                } else {
 280                   nvc0->dirty_3d |= NVC0_NEW_3D_TEXTURES;
 281                   nouveau_bufctx_reset(nvc0->bufctx_3d, NVC0_BIND_3D_TEX(s, i));
 282                }
 283                if (!--ref)
 284                   return ref;
 285             }
 286          }
 287       }
 288
 289       for (s = 0; s < 6; ++s) {
 290          for (i = 0; i < NVC0_MAX_PIPE_CONSTBUFS; ++i) {
 291             if (!(nvc0->constbuf_valid[s] & (1 << i)))
 292                continue;
 293             if (!nvc0->constbuf[s][i].user &&
 294                 nvc0->constbuf[s][i].u.buf == res) {
 295                nvc0->constbuf_dirty[s] |= 1 << i;
 296                if (unlikely(s == 5)) {
 297                   nvc0->dirty_cp |= NVC0_NEW_CP_CONSTBUF;
 298                   nouveau_bufctx_reset(nvc0->bufctx_cp, NVC0_BIND_CP_CB(i));
 299                } else {
 300                   nvc0->dirty_3d |= NVC0_NEW_3D_CONSTBUF;
 301                   nouveau_bufctx_reset(nvc0->bufctx_3d, NVC0_BIND_3D_CB(s, i));
 302                }
 303                if (!--ref)
 304                   return ref;
 305             }
 306          }
 307       }
 308
 309       for (s = 0; s < 6; ++s) {
 310          for (i = 0; i < NVC0_MAX_BUFFERS; ++i) {
 311             if (nvc0->buffers[s][i].buffer == res) {
 312                nvc0->buffers_dirty[s] |= 1 << i;
 313                if (unlikely(s == 5)) {
 314                   nvc0->dirty_cp |= NVC0_NEW_CP_BUFFERS;
 315                   nouveau_bufctx_reset(nvc0->bufctx_cp, NVC0_BIND_CP_BUF);
 316                } else {
 317                   nvc0->dirty_3d |= NVC0_NEW_3D_BUFFERS;
 318                   nouveau_bufctx_reset(nvc0->bufctx_3d, NVC0_BIND_3D_BUF);
 319                }
 320                if (!--ref)
 321                   return ref;
 322             }
 323          }
 324       }
 325
 326       for (s = 0; s < 6; ++s) {
 327          for (i = 0; i < NVC0_MAX_IMAGES; ++i) {
 328             if (nvc0->images[s][i].resource == res) {
 329                nvc0->images_dirty[s] |= 1 << i;
 330                if (unlikely(s == 5)) {
 331                   nvc0->dirty_cp |= NVC0_NEW_CP_SURFACES;
 332                   nouveau_bufctx_reset(nvc0->bufctx_cp, NVC0_BIND_CP_SUF);
 333                } else {
 334                   nvc0->dirty_3d |= NVC0_NEW_3D_SURFACES;
 335                   nouveau_bufctx_reset(nvc0->bufctx_3d, NVC0_BIND_3D_SUF);
 336                }
 337             }
 338             if (!--ref)
 339                return ref;
 340          }
 341       }
 342    }
 343
 344    return ref;
 345 }
 346
 347 static void
 348 nvc0_context_get_sample_position(struct pipe_context *, unsigned, unsigned,
 349                                  float *);
 350
 351 struct pipe_context *
 352 nvc0_create(struct pipe_screen *pscreen, void *priv, unsigned ctxflags)
 353 {
 354    struct nvc0_screen *screen = nvc0_screen(pscreen);
 355    struct nvc0_context *nvc0;
 356    struct pipe_context *pipe;
 357    int ret;
 358    uint32_t flags;
 359
 360    nvc0 = CALLOC_STRUCT(nvc0_context);
 361    if (!nvc0)
 362       return NULL;
 363    pipe = &nvc0->base.pipe;
 364
 365    if (!nvc0_blitctx_create(nvc0))
 366       goto out_err;
 367
 368    nvc0->base.pushbuf = screen->base.pushbuf;
 369    nvc0->base.client = screen->base.client;
 370
 371    ret = nouveau_bufctx_new(screen->base.client, 2, &nvc0->bufctx);
 372    if (!ret)
 373       ret = nouveau_bufctx_new(screen->base.client, NVC0_BIND_3D_COUNT,
 374                                &nvc0->bufctx_3d);
 375    if (!ret)
 376       ret = nouveau_bufctx_new(screen->base.client, NVC0_BIND_CP_COUNT,
 377                                &nvc0->bufctx_cp);
 378    if (ret)
 379       goto out_err;
 380
 381    nvc0->screen = screen;
 382    nvc0->base.screen = &screen->base;
 383
 384    pipe->screen = pscreen;
 385    pipe->priv = priv;
 386
 387    pipe->destroy = nvc0_destroy;
 388
 389    pipe->draw_vbo = nvc0_draw_vbo;
 390    pipe->clear = nvc0_clear;
 391    pipe->launch_grid = (nvc0->screen->base.class_3d >= NVE4_3D_CLASS) ?
 392       nve4_launch_grid : nvc0_launch_grid;
 393
 394    pipe->flush = nvc0_flush;
 395    pipe->texture_barrier = nvc0_texture_barrier;
 396    pipe->memory_barrier = nvc0_memory_barrier;
 397    pipe->get_sample_position = nvc0_context_get_sample_position;
 398    pipe->emit_string_marker = nvc0_emit_string_marker;
 399
 400    nouveau_context_init(&nvc0->base);
 401    nvc0_init_query_functions(nvc0);
 402    nvc0_init_surface_functions(nvc0);
 403    nvc0_init_state_functions(nvc0);
 404    nvc0_init_transfer_functions(nvc0);
 405    nvc0_init_resource_functions(pipe);
 406
 407    nvc0->base.invalidate_resource_storage = nvc0_invalidate_resource_storage;
 408
 409    pipe->create_video_codec = nvc0_create_decoder;
 410    pipe->create_video_buffer = nvc0_video_buffer_create;
 411
 412    /* shader builtin library is per-screen, but we need a context for m2mf */
 413    nvc0_program_library_upload(nvc0);
 414    nvc0_program_init_tcp_empty(nvc0);
 415    if (!nvc0->tcp_empty)
 416       goto out_err;
 417    /* set the empty tctl prog on next draw in case one is never set */
 418    nvc0->dirty_3d |= NVC0_NEW_3D_TCTLPROG;
 419
 420    /* Do not bind the COMPUTE driver constbuf at screen initialization because
 421     * CBs are aliased between 3D and COMPUTE, but make sure it will be bound if
 422     * a grid is launched later. */
 423    nvc0->dirty_cp |= NVC0_NEW_CP_DRIVERCONST;
 424
 425    /* now that there are no more opportunities for errors, set the current
 426     * context if there isn't already one.
 427     */
 428    if (!screen->cur_ctx) {
 429       nvc0->state = screen->save_state;
 430       screen->cur_ctx = nvc0;
 431       nouveau_pushbuf_bufctx(screen->base.pushbuf, nvc0->bufctx);
 432    }
 433    screen->base.pushbuf->kick_notify = nvc0_default_kick_notify;
 434
 435    /* add permanently resident buffers to bufctxts */
 436
 437    flags = NV_VRAM_DOMAIN(&screen->base) | NOUVEAU_BO_RD;
 438
 439    BCTX_REFN_bo(nvc0->bufctx_3d, 3D_SCREEN, flags, screen->text);
 440    BCTX_REFN_bo(nvc0->bufctx_3d, 3D_SCREEN, flags, screen->uniform_bo);
 441    BCTX_REFN_bo(nvc0->bufctx_3d, 3D_SCREEN, flags, screen->txc);
 442    if (screen->compute) {
 443       BCTX_REFN_bo(nvc0->bufctx_cp, CP_SCREEN, flags, screen->text);
 444       BCTX_REFN_bo(nvc0->bufctx_cp, CP_SCREEN, flags, screen->uniform_bo);
 445       BCTX_REFN_bo(nvc0->bufctx_cp, CP_SCREEN, flags, screen->txc);
 446    }
 447
 448    flags = NV_VRAM_DOMAIN(&screen->base) | NOUVEAU_BO_RDWR;
 449
 450    if (screen->poly_cache)
 451       BCTX_REFN_bo(nvc0->bufctx_3d, 3D_SCREEN, flags, screen->poly_cache);
 452    if (screen->compute)
 453       BCTX_REFN_bo(nvc0->bufctx_cp, CP_SCREEN, flags, screen->tls);
 454
 455    flags = NOUVEAU_BO_GART | NOUVEAU_BO_WR;
 456
 457    BCTX_REFN_bo(nvc0->bufctx_3d, 3D_SCREEN, flags, screen->fence.bo);
 458    BCTX_REFN_bo(nvc0->bufctx, FENCE, flags, screen->fence.bo);
 459    if (screen->compute)
 460       BCTX_REFN_bo(nvc0->bufctx_cp, CP_SCREEN, flags, screen->fence.bo);
 461
 462    nvc0->base.scratch.bo_size = 2 << 20;
 463
 464    memset(nvc0->tex_handles, ~0, sizeof(nvc0->tex_handles));
 465
 466    util_dynarray_init(&nvc0->global_residents);
 467
 468    return pipe;
 469
 470 out_err:
 471    if (nvc0) {
 472       if (nvc0->bufctx_3d)
 473          nouveau_bufctx_del(&nvc0->bufctx_3d);
 474       if (nvc0->bufctx_cp)
 475          nouveau_bufctx_del(&nvc0->bufctx_cp);
 476       if (nvc0->bufctx)
 477          nouveau_bufctx_del(&nvc0->bufctx);
 478       FREE(nvc0->blit);
 479       FREE(nvc0);
 480    }
 481    return NULL;
 482 }
 483
 484 void
 485 nvc0_bufctx_fence(struct nvc0_context *nvc0, struct nouveau_bufctx *bufctx,
 486                   bool on_flush)
 487 {
 488    struct nouveau_list *list = on_flush ? &bufctx->current : &bufctx->pending;
 489    struct nouveau_list *it;
 490    NOUVEAU_DRV_STAT_IFD(unsigned count = 0);
 491
 492    for (it = list->next; it != list; it = it->next) {
 493       struct nouveau_bufref *ref = (struct nouveau_bufref *)it;
 494       struct nv04_resource *res = ref->priv;
 495       if (res)
 496          nvc0_resource_validate(res, (unsigned)ref->priv_data);
 497       NOUVEAU_DRV_STAT_IFD(count++);
 498    }
 499    NOUVEAU_DRV_STAT(&nvc0->screen->base, resource_validate_count, count);
 500 }
 501
 502 static void
 503 nvc0_context_get_sample_position(struct pipe_context *pipe,
 504                                  unsigned sample_count, unsigned sample_index,
 505                                  float *xy)
 506 {
 507    static const uint8_t ms1[1][2] = { { 0x8, 0x8 } };
 508    static const uint8_t ms2[2][2] = {
 509       { 0x4, 0x4 }, { 0xc, 0xc } }; /* surface coords (0,0), (1,0) */
 510    static const uint8_t ms4[4][2] = {
 511       { 0x6, 0x2 }, { 0xe, 0x6 },   /* (0,0), (1,0) */
 512       { 0x2, 0xa }, { 0xa, 0xe } }; /* (0,1), (1,1) */
 513    static const uint8_t ms8[8][2] = {
 514       { 0x1, 0x7 }, { 0x5, 0x3 },   /* (0,0), (1,0) */
 515       { 0x3, 0xd }, { 0x7, 0xb },   /* (0,1), (1,1) */
 516       { 0x9, 0x5 }, { 0xf, 0x1 },   /* (2,0), (3,0) */
 517       { 0xb, 0xf }, { 0xd, 0x9 } }; /* (2,1), (3,1) */
 518 #if 0
 519    /* NOTE: there are alternative modes for MS2 and MS8, currently not used */
 520    static const uint8_t ms8_alt[8][2] = {
 521       { 0x9, 0x5 }, { 0x7, 0xb },   /* (2,0), (1,1) */
 522       { 0xd, 0x9 }, { 0x5, 0x3 },   /* (3,1), (1,0) */
 523       { 0x3, 0xd }, { 0x1, 0x7 },   /* (0,1), (0,0) */
 524       { 0xb, 0xf }, { 0xf, 0x1 } }; /* (2,1), (3,0) */
 525 #endif
 526
 527    const uint8_t (*ptr)[2];
 528
 529    switch (sample_count) {
 530    case 0:
 531    case 1: ptr = ms1; break;
 532    case 2: ptr = ms2; break;
 533    case 4: ptr = ms4; break;
 534    case 8: ptr = ms8; break;
 535    default:
 536       assert(0);
 537       return; /* bad sample count -> undefined locations */
 538    }
 539    xy[0] = ptr[sample_index][0] * 0.0625f;
 540    xy[1] = ptr[sample_index][1] * 0.0625f;
 541 }