src/mesa/state_tracker/st_sampler_view.c

   1 /*
   2  * Copyright 2016 VMware, Inc.
   3  * All Rights Reserved.
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a
   6  * copy of this software and associated documentation files (the
   7  * "Software"), to deal in the Software without restriction, including
   8  * without limitation the rights to use, copy, modify, merge, publish,
   9  * distribute, sub license, and/or sell copies of the Software, and to
  10  * permit persons to whom the Software is furnished to do so, subject to
  11  * the following conditions:
  12  *
  13  * The above copyright notice and this permission notice (including the
  14  * next paragraph) shall be included in all copies or substantial portions
  15  * of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  19  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
  20  * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
  21  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  22  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  23  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  24  */
  25
  26 #include "pipe/p_context.h"
  27 #include "util/u_format.h"
  28 #include "util/u_inlines.h"
  29
  30 #include "main/context.h"
  31 #include "main/macros.h"
  32 #include "main/mtypes.h"
  33 #include "main/teximage.h"
  34 #include "main/texobj.h"
  35 #include "program/prog_instruction.h"
  36
  37 #include "st_context.h"
  38 #include "st_sampler_view.h"
  39 #include "st_texture.h"
  40 #include "st_format.h"
  41 #include "st_cb_bufferobjects.h"
  42 #include "st_cb_texture.h"
  43
  44
  45 /**
  46  * Set the given view as the current context's view for the texture.
  47  *
  48  * Overwrites any pre-existing view of the context.
  49  *
  50  * Takes ownership of the view (i.e., stores the view without incrementing the
  51  * reference count).
  52  *
  53  * \return the view, or NULL on error. In case of error, the reference to the
  54  * view is released.
  55  */
  56 static struct pipe_sampler_view *
  57 st_texture_set_sampler_view(struct st_context *st,
  58                             struct st_texture_object *stObj,
  59                             struct pipe_sampler_view *view,
  60                             bool glsl130_or_later, bool srgb_skip_decode)
  61 {
  62    struct st_sampler_views *views;
  63    struct st_sampler_view *free = NULL;
  64    struct st_sampler_view *sv;
  65    GLuint i;
  66
  67    simple_mtx_lock(&stObj->validate_mutex);
  68    views = stObj->sampler_views;
  69
  70    for (i = 0; i < views->count; ++i) {
  71       sv = &views->views[i];
  72
  73       /* Is the array entry used ? */
  74       if (sv->view) {
  75          /* check if the context matches */
  76          if (sv->view->context == st->pipe) {
  77             pipe_sampler_view_release(st->pipe, &sv->view);
  78             goto found;
  79          }
  80       } else {
  81          /* Found a free slot, remember that */
  82          free = sv;
  83       }
  84    }
  85
  86    /* Couldn't find a slot for our context, create a new one */
  87    if (free) {
  88       sv = free;
  89    } else {
  90       if (views->count >= views->max) {
  91          /* Allocate a larger container. */
  92          unsigned new_max = 2 * views->max;
  93          unsigned new_size = sizeof(*views) + new_max * sizeof(views->views[0]);
  94
  95          if (new_max < views->max ||
  96              new_max > (UINT_MAX - sizeof(*views)) / sizeof(views->views[0])) {
  97             pipe_sampler_view_release(st->pipe, &view);
  98             goto out;
  99          }
 100
 101          struct st_sampler_views *new_views = malloc(new_size);
 102          if (!new_views) {
 103             pipe_sampler_view_release(st->pipe, &view);
 104             goto out;
 105          }
 106
 107          new_views->count = views->count;
 108          new_views->max = new_max;
 109          memcpy(&new_views->views[0], &views->views[0],
 110                views->count * sizeof(views->views[0]));
 111
 112          /* Initialize the pipe_sampler_view pointers to zero so that we don't
 113           * have to worry about racing against readers when incrementing
 114           * views->count.
 115           */
 116          memset(&new_views->views[views->count], 0,
 117                 (new_max - views->count) * sizeof(views->views[0]));
 118
 119          /* Use memory release semantics to ensure that concurrent readers will
 120           * get the correct contents of the new container.
 121           *
 122           * Also, the write should be atomic, but that's guaranteed anyway on
 123           * all supported platforms.
 124           */
 125          p_atomic_set(&stObj->sampler_views, new_views);
 126
 127          /* We keep the old container around until the texture object is
 128           * deleted, because another thread may still be reading from it. We
 129           * double the size of the container each time, so we end up with
 130           * at most twice the total memory allocation.
 131           */
 132          views->next = stObj->sampler_views_old;
 133          stObj->sampler_views_old = views;
 134
 135          views = new_views;
 136       }
 137
 138       sv = &views->views[views->count];
 139
 140       /* Since modification is guarded by the lock, only the write part of the
 141        * increment has to be atomic, and that's already guaranteed on all
 142        * supported platforms without using an atomic intrinsic.
 143        */
 144       views->count++;
 145    }
 146
 147 found:
 148    assert(sv->view == NULL);
 149
 150    sv->glsl130_or_later = glsl130_or_later;
 151    sv->srgb_skip_decode = srgb_skip_decode;
 152    sv->view = view;
 153
 154 out:
 155    simple_mtx_unlock(&stObj->validate_mutex);
 156    return view;
 157 }
 158
 159
 160 /**
 161  * Return the most-recently validated sampler view for the texture \p stObj
 162  * in the given context, if any.
 163  *
 164  * Performs no additional validation.
 165  */
 166 const struct st_sampler_view *
 167 st_texture_get_current_sampler_view(const struct st_context *st,
 168                                     const struct st_texture_object *stObj)
 169 {
 170    const struct st_sampler_views *views = p_atomic_read(&stObj->sampler_views);
 171
 172    for (unsigned i = 0; i < views->count; ++i) {
 173       const struct st_sampler_view *sv = &views->views[i];
 174       if (sv->view && sv->view->context == st->pipe)
 175          return sv;
 176    }
 177
 178    return NULL;
 179 }
 180
 181
 182 /**
 183  * For the given texture object, release any sampler views which belong
 184  * to the calling context.  This is used to free any sampler views
 185  * which belong to the context before the context is destroyed.
 186  */
 187 void
 188 st_texture_release_sampler_view(struct st_context *st,
 189                                 struct st_texture_object *stObj)
 190 {
 191    GLuint i;
 192
 193    simple_mtx_lock(&stObj->validate_mutex);
 194    struct st_sampler_views *views = stObj->sampler_views;
 195    for (i = 0; i < views->count; ++i) {
 196       struct pipe_sampler_view **sv = &views->views[i].view;
 197
 198       if (*sv && (*sv)->context == st->pipe) {
 199          pipe_sampler_view_reference(sv, NULL);
 200          break;
 201       }
 202    }
 203    simple_mtx_unlock(&stObj->validate_mutex);
 204 }
 205
 206
 207 /**
 208  * Release all sampler views attached to the given texture object, regardless
 209  * of the context.  This is called fairly frequently.  For example, whenever
 210  * the texture's base level, max level or swizzle change.
 211  */
 212 void
 213 st_texture_release_all_sampler_views(struct st_context *st,
 214                                      struct st_texture_object *stObj)
 215 {
 216    GLuint i;
 217
 218    /* TODO: This happens while a texture is deleted, because the Driver API
 219     * is asymmetric: the driver allocates the texture object memory, but
 220     * mesa/main frees it.
 221     */
 222    if (!stObj->sampler_views)
 223       return;
 224
 225    simple_mtx_lock(&stObj->validate_mutex);
 226    struct st_sampler_views *views = stObj->sampler_views;
 227    for (i = 0; i < views->count; ++i)
 228       pipe_sampler_view_release(st->pipe, &views->views[i].view);
 229    simple_mtx_unlock(&stObj->validate_mutex);
 230 }
 231
 232
 233 /*
 234  * Free the texture's st_sampler_views objects.  This should be called
 235  * after st_texture_release_all_sampler_views().
 236  */
 237 void
 238 st_texture_free_sampler_views(struct st_texture_object *stObj)
 239 {
 240    free(stObj->sampler_views);
 241    stObj->sampler_views = NULL;
 242
 243    while (stObj->sampler_views_old) {
 244       struct st_sampler_views *views = stObj->sampler_views_old;
 245       stObj->sampler_views_old = views->next;
 246       free(views);
 247    }
 248 }
 249
 250
 251 /**
 252  * Return swizzle1(swizzle2)
 253  */
 254 static unsigned
 255 swizzle_swizzle(unsigned swizzle1, unsigned swizzle2)
 256 {
 257    unsigned i, swz[4];
 258
 259    if (swizzle1 == SWIZZLE_XYZW) {
 260       /* identity swizzle, no change to swizzle2 */
 261       return swizzle2;
 262    }
 263
 264    for (i = 0; i < 4; i++) {
 265       unsigned s = GET_SWZ(swizzle1, i);
 266       switch (s) {
 267       case SWIZZLE_X:
 268       case SWIZZLE_Y:
 269       case SWIZZLE_Z:
 270       case SWIZZLE_W:
 271          swz[i] = GET_SWZ(swizzle2, s);
 272          break;
 273       case SWIZZLE_ZERO:
 274          swz[i] = SWIZZLE_ZERO;
 275          break;
 276       case SWIZZLE_ONE:
 277          swz[i] = SWIZZLE_ONE;
 278          break;
 279       default:
 280          assert(!"Bad swizzle term");
 281          swz[i] = SWIZZLE_X;
 282       }
 283    }
 284
 285    return MAKE_SWIZZLE4(swz[0], swz[1], swz[2], swz[3]);
 286 }
 287
 288
 289 /**
 290  * Given a user-specified texture base format, the actual gallium texture
 291  * format and the current GL_DEPTH_MODE, return a texture swizzle.
 292  *
 293  * Consider the case where the user requests a GL_RGB internal texture
 294  * format the driver actually uses an RGBA format.  The A component should
 295  * be ignored and sampling from the texture should always return (r,g,b,1).
 296  * But if we rendered to the texture we might have written A values != 1.
 297  * By sampling the texture with a ".xyz1" swizzle we'll get the expected A=1.
 298  * This function computes the texture swizzle needed to get the expected
 299  * values.
 300  *
 301  * In the case of depth textures, the GL_DEPTH_MODE state determines the
 302  * texture swizzle.
 303  *
 304  * This result must be composed with the user-specified swizzle to get
 305  * the final swizzle.
 306  */
 307 static unsigned
 308 compute_texture_format_swizzle(GLenum baseFormat, GLenum depthMode,
 309                                bool glsl130_or_later)
 310 {
 311    switch (baseFormat) {
 312    case GL_RGBA:
 313       return SWIZZLE_XYZW;
 314    case GL_RGB:
 315       return MAKE_SWIZZLE4(SWIZZLE_X, SWIZZLE_Y, SWIZZLE_Z, SWIZZLE_ONE);
 316    case GL_RG:
 317       return MAKE_SWIZZLE4(SWIZZLE_X, SWIZZLE_Y, SWIZZLE_ZERO, SWIZZLE_ONE);
 318    case GL_RED:
 319       return MAKE_SWIZZLE4(SWIZZLE_X, SWIZZLE_ZERO,
 320                            SWIZZLE_ZERO, SWIZZLE_ONE);
 321    case GL_ALPHA:
 322       return MAKE_SWIZZLE4(SWIZZLE_ZERO, SWIZZLE_ZERO,
 323                            SWIZZLE_ZERO, SWIZZLE_W);
 324    case GL_LUMINANCE:
 325       return MAKE_SWIZZLE4(SWIZZLE_X, SWIZZLE_X, SWIZZLE_X, SWIZZLE_ONE);
 326    case GL_LUMINANCE_ALPHA:
 327       return MAKE_SWIZZLE4(SWIZZLE_X, SWIZZLE_X, SWIZZLE_X, SWIZZLE_W);
 328    case GL_INTENSITY:
 329       return SWIZZLE_XXXX;
 330    case GL_STENCIL_INDEX:
 331    case GL_DEPTH_STENCIL:
 332    case GL_DEPTH_COMPONENT:
 333       /* Now examine the depth mode */
 334       switch (depthMode) {
 335       case GL_LUMINANCE:
 336          return MAKE_SWIZZLE4(SWIZZLE_X, SWIZZLE_X, SWIZZLE_X, SWIZZLE_ONE);
 337       case GL_INTENSITY:
 338          return MAKE_SWIZZLE4(SWIZZLE_X, SWIZZLE_X, SWIZZLE_X, SWIZZLE_X);
 339       case GL_ALPHA:
 340          /* The texture(sampler*Shadow) functions from GLSL 1.30 ignore
 341           * the depth mode and return float, while older shadow* functions
 342           * and ARB_fp instructions return vec4 according to the depth mode.
 343           *
 344           * The problem with the GLSL 1.30 functions is that GL_ALPHA forces
 345           * them to return 0, breaking them completely.
 346           *
 347           * A proper fix would increase code complexity and that's not worth
 348           * it for a rarely used feature such as the GL_ALPHA depth mode
 349           * in GL3. Therefore, change GL_ALPHA to GL_INTENSITY for all
 350           * shaders that use GLSL 1.30 or later.
 351           *
 352           * BTW, it's required that sampler views are updated when
 353           * shaders change (check_sampler_swizzle takes care of that).
 354           */
 355          if (glsl130_or_later)
 356             return SWIZZLE_XXXX;
 357          else
 358             return MAKE_SWIZZLE4(SWIZZLE_ZERO, SWIZZLE_ZERO,
 359                                  SWIZZLE_ZERO, SWIZZLE_X);
 360       case GL_RED:
 361          return MAKE_SWIZZLE4(SWIZZLE_X, SWIZZLE_ZERO,
 362                               SWIZZLE_ZERO, SWIZZLE_ONE);
 363       default:
 364          assert(!"Unexpected depthMode");
 365          return SWIZZLE_XYZW;
 366       }
 367    default:
 368       assert(!"Unexpected baseFormat");
 369       return SWIZZLE_XYZW;
 370    }
 371 }
 372
 373
 374 static unsigned
 375 get_texture_format_swizzle(const struct st_context *st,
 376                            const struct st_texture_object *stObj,
 377                            bool glsl130_or_later)
 378 {
 379    GLenum baseFormat = _mesa_base_tex_image(&stObj->base)->_BaseFormat;
 380    unsigned tex_swizzle;
 381    GLenum depth_mode = stObj->base.DepthMode;
 382
 383    /* In ES 3.0, DEPTH_TEXTURE_MODE is expected to be GL_RED for textures
 384     * with depth component data specified with a sized internal format.
 385     */
 386    if (_mesa_is_gles3(st->ctx) &&
 387        (baseFormat == GL_DEPTH_COMPONENT ||
 388         baseFormat == GL_DEPTH_STENCIL ||
 389         baseFormat == GL_STENCIL_INDEX)) {
 390       const struct gl_texture_image *firstImage =
 391          _mesa_base_tex_image(&stObj->base);
 392       if (firstImage->InternalFormat != GL_DEPTH_COMPONENT &&
 393           firstImage->InternalFormat != GL_DEPTH_STENCIL &&
 394           firstImage->InternalFormat != GL_STENCIL_INDEX)
 395          depth_mode = GL_RED;
 396    }
 397    tex_swizzle = compute_texture_format_swizzle(baseFormat,
 398                                                 depth_mode,
 399                                                 glsl130_or_later);
 400
 401    /* Combine the texture format swizzle with user's swizzle */
 402    return swizzle_swizzle(stObj->base._Swizzle, tex_swizzle);
 403 }
 404
 405
 406 /**
 407  * Return TRUE if the texture's sampler view swizzle is not equal to
 408  * the texture's swizzle.
 409  *
 410  * \param stObj  the st texture object,
 411  */
 412 MAYBE_UNUSED static boolean
 413 check_sampler_swizzle(const struct st_context *st,
 414                       const struct st_texture_object *stObj,
 415                       const struct pipe_sampler_view *sv,
 416                       bool glsl130_or_later)
 417 {
 418    unsigned swizzle = get_texture_format_swizzle(st, stObj, glsl130_or_later);
 419
 420    return ((sv->swizzle_r != GET_SWZ(swizzle, 0)) ||
 421            (sv->swizzle_g != GET_SWZ(swizzle, 1)) ||
 422            (sv->swizzle_b != GET_SWZ(swizzle, 2)) ||
 423            (sv->swizzle_a != GET_SWZ(swizzle, 3)));
 424 }
 425
 426
 427 static unsigned
 428 last_level(const struct st_texture_object *stObj)
 429 {
 430    unsigned ret = MIN2(stObj->base.MinLevel + stObj->base._MaxLevel,
 431                        stObj->pt->last_level);
 432    if (stObj->base.Immutable)
 433       ret = MIN2(ret, stObj->base.MinLevel + stObj->base.NumLevels - 1);
 434    return ret;
 435 }
 436
 437
 438 static unsigned
 439 last_layer(const struct st_texture_object *stObj)
 440 {
 441    if (stObj->base.Immutable && stObj->pt->array_size > 1)
 442       return MIN2(stObj->base.MinLayer + stObj->base.NumLayers - 1,
 443                   stObj->pt->array_size - 1);
 444    return stObj->pt->array_size - 1;
 445 }
 446
 447
 448 /**
 449  * Determine the format for the texture sampler view.
 450  */
 451 static enum pipe_format
 452 get_sampler_view_format(struct st_context *st,
 453                         const struct st_texture_object *stObj,
 454                         bool srgb_skip_decode)
 455 {
 456    enum pipe_format format;
 457
 458    GLenum baseFormat = _mesa_base_tex_image(&stObj->base)->_BaseFormat;
 459    format = stObj->surface_based ? stObj->surface_format : stObj->pt->format;
 460
 461    if (baseFormat == GL_DEPTH_COMPONENT ||
 462        baseFormat == GL_DEPTH_STENCIL ||
 463        baseFormat == GL_STENCIL_INDEX) {
 464       if (stObj->base.StencilSampling || baseFormat == GL_STENCIL_INDEX)
 465          format = util_format_stencil_only(format);
 466
 467       return format;
 468    }
 469
 470    /* If sRGB decoding is off, use the linear format */
 471    if (srgb_skip_decode)
 472       format = util_format_linear(format);
 473
 474    /* Use R8_UNORM for video formats */
 475    switch (format) {
 476    case PIPE_FORMAT_NV12:
 477    case PIPE_FORMAT_IYUV:
 478       format = PIPE_FORMAT_R8_UNORM;
 479       break;
 480    default:
 481       break;
 482    }
 483    return format;
 484 }
 485
 486
 487 static struct pipe_sampler_view *
 488 st_create_texture_sampler_view_from_stobj(struct st_context *st,
 489                                           struct st_texture_object *stObj,
 490                                           enum pipe_format format,
 491                                           bool glsl130_or_later)
 492 {
 493    /* There is no need to clear this structure (consider CPU overhead). */
 494    struct pipe_sampler_view templ;
 495    unsigned swizzle = get_texture_format_swizzle(st, stObj, glsl130_or_later);
 496
 497    templ.format = format;
 498
 499    if (stObj->level_override) {
 500       templ.u.tex.first_level = templ.u.tex.last_level = stObj->level_override;
 501    } else {
 502       templ.u.tex.first_level = stObj->base.MinLevel + stObj->base.BaseLevel;
 503       templ.u.tex.last_level = last_level(stObj);
 504    }
 505    if (stObj->layer_override) {
 506       templ.u.tex.first_layer = templ.u.tex.last_layer = stObj->layer_override;
 507    } else {
 508       templ.u.tex.first_layer = stObj->base.MinLayer;
 509       templ.u.tex.last_layer = last_layer(stObj);
 510    }
 511    assert(templ.u.tex.first_layer <= templ.u.tex.last_layer);
 512    assert(templ.u.tex.first_level <= templ.u.tex.last_level);
 513    templ.target = gl_target_to_pipe(stObj->base.Target);
 514
 515    templ.swizzle_r = GET_SWZ(swizzle, 0);
 516    templ.swizzle_g = GET_SWZ(swizzle, 1);
 517    templ.swizzle_b = GET_SWZ(swizzle, 2);
 518    templ.swizzle_a = GET_SWZ(swizzle, 3);
 519
 520    return st->pipe->create_sampler_view(st->pipe, stObj->pt, &templ);
 521 }
 522
 523
 524 struct pipe_sampler_view *
 525 st_get_texture_sampler_view_from_stobj(struct st_context *st,
 526                                        struct st_texture_object *stObj,
 527                                        const struct gl_sampler_object *samp,
 528                                        bool glsl130_or_later,
 529                                        bool ignore_srgb_decode)
 530 {
 531    const struct st_sampler_view *sv;
 532    bool srgb_skip_decode = false;
 533
 534    if (!ignore_srgb_decode && samp->sRGBDecode == GL_SKIP_DECODE_EXT)
 535       srgb_skip_decode = true;
 536
 537    sv = st_texture_get_current_sampler_view(st, stObj);
 538
 539    if (sv &&
 540        sv->glsl130_or_later == glsl130_or_later &&
 541        sv->srgb_skip_decode == srgb_skip_decode) {
 542       /* Debug check: make sure that the sampler view's parameters are
 543        * what they're supposed to be.
 544        */
 545       struct pipe_sampler_view *view = sv->view;
 546       assert(stObj->pt == view->texture);
 547       assert(!check_sampler_swizzle(st, stObj, view, glsl130_or_later));
 548       assert(get_sampler_view_format(st, stObj, srgb_skip_decode) == view->format);
 549       assert(gl_target_to_pipe(stObj->base.Target) == view->target);
 550       assert(stObj->level_override ||
 551              stObj->base.MinLevel + stObj->base.BaseLevel == view->u.tex.first_level);
 552       assert(stObj->level_override || last_level(stObj) == view->u.tex.last_level);
 553       assert(stObj->layer_override || stObj->base.MinLayer == view->u.tex.first_layer);
 554       assert(stObj->layer_override || last_layer(stObj) == view->u.tex.last_layer);
 555       assert(!stObj->layer_override ||
 556              (stObj->layer_override == view->u.tex.first_layer &&
 557               stObj->layer_override == view->u.tex.last_layer));
 558       return view;
 559    }
 560
 561    /* create new sampler view */
 562    enum pipe_format format = get_sampler_view_format(st, stObj,
 563                                                      srgb_skip_decode);
 564    struct pipe_sampler_view *view =
 565          st_create_texture_sampler_view_from_stobj(st, stObj, format,
 566                                                    glsl130_or_later);
 567
 568    view = st_texture_set_sampler_view(st, stObj, view,
 569                                       glsl130_or_later, srgb_skip_decode);
 570
 571    return view;
 572 }
 573
 574
 575 struct pipe_sampler_view *
 576 st_get_buffer_sampler_view_from_stobj(struct st_context *st,
 577                                       struct st_texture_object *stObj)
 578 {
 579    const struct st_sampler_view *sv;
 580    struct st_buffer_object *stBuf =
 581       st_buffer_object(stObj->base.BufferObject);
 582
 583    if (!stBuf || !stBuf->buffer)
 584       return NULL;
 585
 586    sv = st_texture_get_current_sampler_view(st, stObj);
 587
 588    struct pipe_resource *buf = stBuf->buffer;
 589
 590    if (sv) {
 591       struct pipe_sampler_view *view = sv->view;
 592
 593       if (view->texture == buf) {
 594          /* Debug check: make sure that the sampler view's parameters are
 595           * what they're supposed to be.
 596           */
 597          assert(st_mesa_format_to_pipe_format(st,
 598                                               stObj->base._BufferObjectFormat)
 599              == view->format);
 600          assert(view->target == PIPE_BUFFER);
 601          unsigned base = stObj->base.BufferOffset;
 602          MAYBE_UNUSED unsigned size = MIN2(buf->width0 - base,
 603                            (unsigned) stObj->base.BufferSize);
 604          assert(view->u.buf.offset == base);
 605          assert(view->u.buf.size == size);
 606          return view;
 607       }
 608    }
 609
 610    unsigned base = stObj->base.BufferOffset;
 611
 612    if (base >= buf->width0)
 613       return NULL;
 614
 615    unsigned size = buf->width0 - base;
 616    size = MIN2(size, (unsigned)stObj->base.BufferSize);
 617    if (!size)
 618       return NULL;
 619
 620    /* Create a new sampler view. There is no need to clear the entire
 621     * structure (consider CPU overhead).
 622     */
 623    struct pipe_sampler_view templ;
 624
 625    templ.format =
 626       st_mesa_format_to_pipe_format(st, stObj->base._BufferObjectFormat);
 627    templ.target = PIPE_BUFFER;
 628    templ.swizzle_r = PIPE_SWIZZLE_X;
 629    templ.swizzle_g = PIPE_SWIZZLE_Y;
 630    templ.swizzle_b = PIPE_SWIZZLE_Z;
 631    templ.swizzle_a = PIPE_SWIZZLE_W;
 632    templ.u.buf.offset = base;
 633    templ.u.buf.size = size;
 634
 635    struct pipe_sampler_view *view =
 636       st->pipe->create_sampler_view(st->pipe, buf, &templ);
 637
 638    view = st_texture_set_sampler_view(st, stObj, view, false, false);
 639
 640    return view;
 641 }