[mesa.git] / src / mesa / drivers / dri / i965 / intel_context.c

/**************************************************************************
 * 
 * Copyright 2003 Tungsten Graphics, Inc., Cedar Park, Texas.
 * All Rights Reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sub license, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
 * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 * 
 **************************************************************************/


#include "main/glheader.h"
#include "main/context.h"
#include "main/extensions.h"
#include "main/fbobject.h"
#include "main/framebuffer.h"
#include "main/imports.h"
#include "main/renderbuffer.h"

#include "swrast/swrast.h"
#include "swrast_setup/swrast_setup.h"
#include "tnl/tnl.h"
#include "drivers/common/driverfuncs.h"
#include "drivers/common/meta.h"

#include "intel_chipset.h"
#include "intel_buffers.h"
#include "intel_tex.h"
#include "intel_batchbuffer.h"
#include "intel_pixel.h"
#include "intel_regions.h"
#include "intel_buffer_objects.h"
#include "intel_fbo.h"
#include "intel_bufmgr.h"
#include "intel_screen.h"
#include "intel_mipmap_tree.h"

#include "utils.h"
#include "../glsl/ralloc.h"

#ifndef INTEL_DEBUG
int INTEL_DEBUG = (0);
#endif


static const GLubyte *
intelGetString(struct gl_context * ctx, GLenum name)
{
   const struct brw_context *const brw = brw_context(ctx);
   const char *chipset;
   static char buffer[128];

   switch (name) {
   case GL_VENDOR:
      return (GLubyte *) "Intel Open Source Technology Center";
      break;

   case GL_RENDERER:
      switch (brw->intelScreen->deviceID) {
#undef CHIPSET
#define CHIPSET(id, symbol, str) case id: chipset = str; break;
#include "pci_ids/i965_pci_ids.h"
      default:
         chipset = "Unknown Intel Chipset";
         break;
      }

      (void) driGetRendererString(buffer, chipset, 0);
      return (GLubyte *) buffer;

   default:
      return NULL;
   }
}

void
intel_resolve_for_dri2_flush(struct brw_context *brw,
                             __DRIdrawable *drawable)
{
   if (brw->gen < 6) {
      /* MSAA and fast color clear are not supported, so don't waste time
       * checking whether a resolve is needed.
       */
      return;
   }

   struct gl_framebuffer *fb = drawable->driverPrivate;
   struct intel_renderbuffer *rb;

   /* Usually, only the back buffer will need to be downsampled. However,
    * the front buffer will also need it if the user has rendered into it.
    */
   static const gl_buffer_index buffers[2] = {
         BUFFER_BACK_LEFT,
         BUFFER_FRONT_LEFT,
   };

   for (int i = 0; i < 2; ++i) {
      rb = intel_get_renderbuffer(fb, buffers[i]);
      if (rb == NULL || rb->mt == NULL)
         continue;
      if (rb->mt->num_samples <= 1)
         intel_miptree_resolve_color(brw, rb->mt);
      else
         intel_miptree_downsample(brw, rb->mt);
   }
}

static void
intel_flush_front(struct gl_context *ctx)
{
   struct brw_context *brw = brw_context(ctx);
    __DRIcontext *driContext = brw->driContext;
    __DRIdrawable *driDrawable = driContext->driDrawablePriv;
    __DRIscreen *const screen = brw->intelScreen->driScrnPriv;

    if (brw->front_buffer_dirty && _mesa_is_winsys_fbo(ctx->DrawBuffer)) {
      if (screen->dri2.loader->flushFrontBuffer != NULL &&
          driDrawable &&
          driDrawable->loaderPrivate) {

         /* Resolve before flushing FAKE_FRONT_LEFT to FRONT_LEFT.
          *
          * This potentially resolves both front and back buffer. It
          * is unnecessary to resolve the back, but harms nothing except
          * performance. And no one cares about front-buffer render
          * performance.
          */
         intel_resolve_for_dri2_flush(brw, driDrawable);
         intel_batchbuffer_flush(brw);

         screen->dri2.loader->flushFrontBuffer(driDrawable,
                                               driDrawable->loaderPrivate);

         /* We set the dirty bit in intel_prepare_render() if we're
          * front buffer rendering once we get there.
          */
         brw->front_buffer_dirty = false;
      }
   }
}

static unsigned
intel_bits_per_pixel(const struct intel_renderbuffer *rb)
{
   return _mesa_get_format_bytes(intel_rb_format(rb)) * 8;
}

static void
intel_query_dri2_buffers(struct brw_context *brw,
                         __DRIdrawable *drawable,
                         __DRIbuffer **buffers,
                         int *count);

static void
intel_process_dri2_buffer(struct brw_context *brw,
                          __DRIdrawable *drawable,
                          __DRIbuffer *buffer,
                          struct intel_renderbuffer *rb,
                          const char *buffer_name);

void
intel_update_renderbuffers(__DRIcontext *context, __DRIdrawable *drawable)
{
   struct gl_framebuffer *fb = drawable->driverPrivate;
   struct intel_renderbuffer *rb;
   struct brw_context *brw = context->driverPrivate;
   __DRIbuffer *buffers = NULL;
   int i, count;
   const char *region_name;

   /* Set this up front, so that in case our buffers get invalidated
    * while we're getting new buffers, we don't clobber the stamp and
    * thus ignore the invalidate. */
   drawable->lastStamp = drawable->dri2.stamp;

   if (unlikely(INTEL_DEBUG & DEBUG_DRI))
      fprintf(stderr, "enter %s, drawable %p\n", __func__, drawable);

   intel_query_dri2_buffers(brw, drawable, &buffers, &count);

   if (buffers == NULL)
      return;

   for (i = 0; i < count; i++) {
       switch (buffers[i].attachment) {
       case __DRI_BUFFER_FRONT_LEFT:
           rb = intel_get_renderbuffer(fb, BUFFER_FRONT_LEFT);
           region_name = "dri2 front buffer";
           break;

       case __DRI_BUFFER_FAKE_FRONT_LEFT:
           rb = intel_get_renderbuffer(fb, BUFFER_FRONT_LEFT);
           region_name = "dri2 fake front buffer";
           break;

       case __DRI_BUFFER_BACK_LEFT:
           rb = intel_get_renderbuffer(fb, BUFFER_BACK_LEFT);
           region_name = "dri2 back buffer";
           break;

       case __DRI_BUFFER_DEPTH:
       case __DRI_BUFFER_HIZ:
       case __DRI_BUFFER_DEPTH_STENCIL:
       case __DRI_BUFFER_STENCIL:
       case __DRI_BUFFER_ACCUM:
       default:
           fprintf(stderr,
                   "unhandled buffer attach event, attachment type %d\n",
                   buffers[i].attachment);
           return;
       }

       intel_process_dri2_buffer(brw, drawable, &buffers[i], rb, region_name);
   }

   driUpdateFramebufferSize(&brw->ctx, drawable);
}

/**
 * intel_prepare_render should be called anywhere that curent read/drawbuffer
 * state is required.
 */
void
intel_prepare_render(struct brw_context *brw)
{
   __DRIcontext *driContext = brw->driContext;
   __DRIdrawable *drawable;

   drawable = driContext->driDrawablePriv;
   if (drawable && drawable->dri2.stamp != driContext->dri2.draw_stamp) {
      if (drawable->lastStamp != drawable->dri2.stamp)
         intel_update_renderbuffers(driContext, drawable);
      driContext->dri2.draw_stamp = drawable->dri2.stamp;
   }

   drawable = driContext->driReadablePriv;
   if (drawable && drawable->dri2.stamp != driContext->dri2.read_stamp) {
      if (drawable->lastStamp != drawable->dri2.stamp)
         intel_update_renderbuffers(driContext, drawable);
      driContext->dri2.read_stamp = drawable->dri2.stamp;
   }

   /* If we're currently rendering to the front buffer, the rendering
    * that will happen next will probably dirty the front buffer.  So
    * mark it as dirty here.
    */
   if (brw->is_front_buffer_rendering)
      brw->front_buffer_dirty = true;

   /* Wait for the swapbuffers before the one we just emitted, so we
    * don't get too many swaps outstanding for apps that are GPU-heavy
    * but not CPU-heavy.
    *
    * We're using intelDRI2Flush (called from the loader before
    * swapbuffer) and glFlush (for front buffer rendering) as the
    * indicator that a frame is done and then throttle when we get
    * here as we prepare to render the next frame.  At this point for
    * round trips for swap/copy and getting new buffers are done and
    * we'll spend less time waiting on the GPU.
    *
    * Unfortunately, we don't have a handle to the batch containing
    * the swap, and getting our hands on that doesn't seem worth it,
    * so we just us the first batch we emitted after the last swap.
    */
   if (brw->need_throttle && brw->first_post_swapbuffers_batch) {
      if (!brw->disable_throttling)
         drm_intel_bo_wait_rendering(brw->first_post_swapbuffers_batch);
      drm_intel_bo_unreference(brw->first_post_swapbuffers_batch);
      brw->first_post_swapbuffers_batch = NULL;
      brw->need_throttle = false;
   }
}

static void
intel_viewport(struct gl_context *ctx, GLint x, GLint y, GLsizei w, GLsizei h)
{
    struct brw_context *brw = brw_context(ctx);
    __DRIcontext *driContext = brw->driContext;

    if (brw->saved_viewport)
        brw->saved_viewport(ctx, x, y, w, h);

    if (_mesa_is_winsys_fbo(ctx->DrawBuffer)) {
       dri2InvalidateDrawable(driContext->driDrawablePriv);
       dri2InvalidateDrawable(driContext->driReadablePriv);
    }
}

static const struct dri_debug_control debug_control[] = {
   { "tex",   DEBUG_TEXTURE},
   { "state", DEBUG_STATE},
   { "ioctl", DEBUG_IOCTL},
   { "blit",  DEBUG_BLIT},
   { "mip",   DEBUG_MIPTREE},
   { "fall",  DEBUG_PERF},
   { "perf",  DEBUG_PERF},
   { "bat",   DEBUG_BATCH},
   { "pix",   DEBUG_PIXEL},
   { "buf",   DEBUG_BUFMGR},
   { "reg",   DEBUG_REGION},
   { "fbo",   DEBUG_FBO},
   { "fs",    DEBUG_WM },
   { "gs",    DEBUG_GS},
   { "sync",  DEBUG_SYNC},
   { "prim",  DEBUG_PRIMS },
   { "vert",  DEBUG_VERTS },
   { "dri",   DEBUG_DRI },
   { "sf",    DEBUG_SF },
   { "stats", DEBUG_STATS },
   { "wm",    DEBUG_WM },
   { "urb",   DEBUG_URB },
   { "vs",    DEBUG_VS },
   { "clip",  DEBUG_CLIP },
   { "aub",   DEBUG_AUB },
   { "shader_time", DEBUG_SHADER_TIME },
   { "no16",  DEBUG_NO16 },
   { "blorp", DEBUG_BLORP },
   { "vue",   DEBUG_VUE },
   { NULL,    0 }
};


static void
intelInvalidateState(struct gl_context * ctx, GLuint new_state)
{
   struct brw_context *brw = brw_context(ctx);

    if (ctx->swrast_context)
       _swrast_InvalidateState(ctx, new_state);
   _vbo_InvalidateState(ctx, new_state);

   brw->NewGLState |= new_state;
}

static void
intel_glFlush(struct gl_context *ctx)
{
   struct brw_context *brw = brw_context(ctx);

   intel_batchbuffer_flush(brw);
   intel_flush_front(ctx);
   if (brw->is_front_buffer_rendering)
      brw->need_throttle = true;
}

void
intelFinish(struct gl_context * ctx)
{
   struct brw_context *brw = brw_context(ctx);

   intel_glFlush(ctx);

   if (brw->batch.last_bo)
      drm_intel_bo_wait_rendering(brw->batch.last_bo);
}

void
intelInitDriverFunctions(struct dd_function_table *functions)
{
   _mesa_init_driver_functions(functions);

   functions->Flush = intel_glFlush;
   functions->Finish = intelFinish;
   functions->GetString = intelGetString;
   functions->UpdateState = intelInvalidateState;

   intelInitTextureFuncs(functions);
   intelInitTextureImageFuncs(functions);
   intelInitTextureSubImageFuncs(functions);
   intelInitTextureCopyImageFuncs(functions);
   intelInitClearFuncs(functions);
   intelInitBufferFuncs(functions);
   intelInitPixelFuncs(functions);
   intelInitBufferObjectFuncs(functions);
   intel_init_syncobj_functions(functions);
   brw_init_object_purgeable_functions(functions);
}

bool
intelInitContext(struct brw_context *brw,
                 int api,
                 unsigned major_version,
                 unsigned minor_version,
                 const struct gl_config * mesaVis,
                 __DRIcontext * driContextPriv,
                 void *sharedContextPrivate,
                 struct dd_function_table *functions,
                 unsigned *dri_ctx_error)
{
   struct gl_context *ctx = &brw->ctx;
   struct gl_context *shareCtx = (struct gl_context *) sharedContextPrivate;
   __DRIscreen *sPriv = driContextPriv->driScreenPriv;
   struct intel_screen *intelScreen = sPriv->driverPrivate;
   int bo_reuse_mode;
   struct gl_config visual;

   /* Can't rely on invalidate events, fall back to glViewport hack */
   if (!driContextPriv->driScreenPriv->dri2.useInvalidate) {
      brw->saved_viewport = functions->Viewport;
      functions->Viewport = intel_viewport;
   }

   if (mesaVis == NULL) {
      memset(&visual, 0, sizeof visual);
      mesaVis = &visual;
   }

   brw->intelScreen = intelScreen;
   brw->bufmgr = intelScreen->bufmgr;

   if (!_mesa_initialize_context(&brw->ctx, api, mesaVis, shareCtx,
                                 functions)) {
      *dri_ctx_error = __DRI_CTX_ERROR_NO_MEMORY;
      printf("%s: failed to init mesa context\n", __FUNCTION__);
      return false;
   }

   driContextPriv->driverPrivate = brw;
   brw->driContext = driContextPriv;

   brw->gen = intelScreen->gen;

   const int devID = intelScreen->deviceID;
   if (IS_SNB_GT1(devID) || IS_IVB_GT1(devID) || IS_HSW_GT1(devID))
      brw->gt = 1;
   else if (IS_SNB_GT2(devID) || IS_IVB_GT2(devID) || IS_HSW_GT2(devID))
      brw->gt = 2;
   else if (IS_HSW_GT3(devID))
      brw->gt = 3;
   else
      brw->gt = 0;

   if (IS_HASWELL(devID)) {
      brw->is_haswell = true;
   } else if (IS_BAYTRAIL(devID)) {
      brw->is_baytrail = true;
      brw->gt = 1;
   } else if (IS_G4X(devID)) {
      brw->is_g4x = true;
   }

   brw->has_separate_stencil = brw->intelScreen->hw_has_separate_stencil;
   brw->must_use_separate_stencil = brw->intelScreen->hw_must_use_separate_stencil;
   brw->has_hiz = brw->gen >= 6;
   brw->has_llc = brw->intelScreen->hw_has_llc;
   brw->has_swizzling = brw->intelScreen->hw_has_swizzling;

   memset(&ctx->TextureFormatSupported,
          0, sizeof(ctx->TextureFormatSupported));

   driParseConfigFiles(&brw->optionCache, &intelScreen->optionCache,
                       sPriv->myNum, "i965");

   /* Estimate the size of the mappable aperture into the GTT.  There's an
    * ioctl to get the whole GTT size, but not one to get the mappable subset.
    * It turns out it's basically always 256MB, though some ancient hardware
    * was smaller.
    */
   uint32_t gtt_size = 256 * 1024 * 1024;

   /* We don't want to map two objects such that a memcpy between them would
    * just fault one mapping in and then the other over and over forever.  So
    * we would need to divide the GTT size by 2.  Additionally, some GTT is
    * taken up by things like the framebuffer and the ringbuffer and such, so
    * be more conservative.
    */
   brw->max_gtt_map_object_size = gtt_size / 4;

   bo_reuse_mode = driQueryOptioni(&brw->optionCache, "bo_reuse");
   switch (bo_reuse_mode) {
   case DRI_CONF_BO_REUSE_DISABLED:
      break;
   case DRI_CONF_BO_REUSE_ALL:
      intel_bufmgr_gem_enable_reuse(brw->bufmgr);
      break;
   }

   /* Initialize the software rasterizer and helper modules.
    *
    * As of GL 3.1 core, the gen4+ driver doesn't need the swrast context for
    * software fallbacks (which we have to support on legacy GL to do weird
    * glDrawPixels(), glBitmap(), and other functions).
    */
   if (api != API_OPENGL_CORE && api != API_OPENGLES2) {
      _swrast_CreateContext(ctx);
   }

   _vbo_CreateContext(ctx);
   if (ctx->swrast_context) {
      _tnl_CreateContext(ctx);
      _swsetup_CreateContext(ctx);

      /* Configure swrast to match hardware characteristics: */
      _swrast_allow_pixel_fog(ctx, false);
      _swrast_allow_vertex_fog(ctx, true);
   }

   _mesa_meta_init(ctx);

   intelInitExtensions(ctx);

   INTEL_DEBUG = driParseDebugString(getenv("INTEL_DEBUG"), debug_control);
   if (INTEL_DEBUG & DEBUG_BUFMGR)
      dri_bufmgr_set_debug(brw->bufmgr, true);
   if ((INTEL_DEBUG & DEBUG_SHADER_TIME) && brw->gen < 7) {
      fprintf(stderr,
              "shader_time debugging requires gen7 (Ivybridge) or better.\n");
      INTEL_DEBUG &= ~DEBUG_SHADER_TIME;
   }
   if (INTEL_DEBUG & DEBUG_PERF)
      brw->perf_debug = true;

   if (INTEL_DEBUG & DEBUG_AUB)
      drm_intel_bufmgr_gem_set_aub_dump(brw->bufmgr, true);

   intel_batchbuffer_init(brw);

   intel_fbo_init(brw);

   if (!driQueryOptionb(&brw->optionCache, "hiz")) {
       brw->has_hiz = false;
       /* On gen6, you can only do separate stencil with HIZ. */
       if (brw->gen == 6)
          brw->has_separate_stencil = false;
   }

   if (driQueryOptionb(&brw->optionCache, "always_flush_batch")) {
      fprintf(stderr, "flushing batchbuffer before/after each draw call\n");
      brw->always_flush_batch = 1;
   }

   if (driQueryOptionb(&brw->optionCache, "always_flush_cache")) {
      fprintf(stderr, "flushing GPU caches before/after each draw call\n");
      brw->always_flush_cache = 1;
   }

   if (driQueryOptionb(&brw->optionCache, "disable_throttling")) {
      fprintf(stderr, "disabling flush throttling\n");
      brw->disable_throttling = 1;
   }

   return true;
}

void
intelDestroyContext(__DRIcontext * driContextPriv)
{
   struct brw_context *brw =
      (struct brw_context *) driContextPriv->driverPrivate;
   struct gl_context *ctx = &brw->ctx;

   assert(brw); /* should never be null */
   if (brw) {
      /* Dump a final BMP in case the application doesn't call SwapBuffers */
      if (INTEL_DEBUG & DEBUG_AUB) {
         intel_batchbuffer_flush(brw);
         aub_dump_bmp(&brw->ctx);
      }

      _mesa_meta_free(&brw->ctx);

      brw->vtbl.destroy(brw);

      if (ctx->swrast_context) {
         _swsetup_DestroyContext(&brw->ctx);
         _tnl_DestroyContext(&brw->ctx);
      }
      _vbo_DestroyContext(&brw->ctx);

      if (ctx->swrast_context)
         _swrast_DestroyContext(&brw->ctx);

      intel_batchbuffer_free(brw);

      drm_intel_bo_unreference(brw->first_post_swapbuffers_batch);
      brw->first_post_swapbuffers_batch = NULL;

      driDestroyOptionCache(&brw->optionCache);

      /* free the Mesa context */
      _mesa_free_context_data(&brw->ctx);

      ralloc_free(brw);
      driContextPriv->driverPrivate = NULL;
   }
}

GLboolean
intelUnbindContext(__DRIcontext * driContextPriv)
{
   /* Unset current context and dispath table */
   _mesa_make_current(NULL, NULL, NULL);

   return true;
}

/**
 * Fixes up the context for GLES23 with our default-to-sRGB-capable behavior
 * on window system framebuffers.
 *
 * Desktop GL is fairly reasonable in its handling of sRGB: You can ask if
 * your renderbuffer can do sRGB encode, and you can flip a switch that does
 * sRGB encode if the renderbuffer can handle it.  You can ask specifically
 * for a visual where you're guaranteed to be capable, but it turns out that
 * everyone just makes all their ARGB8888 visuals capable and doesn't offer
 * incapable ones, becuase there's no difference between the two in resources
 * used.  Applications thus get built that accidentally rely on the default
 * visual choice being sRGB, so we make ours sRGB capable.  Everything sounds
 * great...
 *
 * But for GLES2/3, they decided that it was silly to not turn on sRGB encode
 * for sRGB renderbuffers you made with the GL_EXT_texture_sRGB equivalent.
 * So they removed the enable knob and made it "if the renderbuffer is sRGB
 * capable, do sRGB encode".  Then, for your window system renderbuffers, you
 * can ask for sRGB visuals and get sRGB encode, or not ask for sRGB visuals
 * and get no sRGB encode (assuming that both kinds of visual are available).
 * Thus our choice to support sRGB by default on our visuals for desktop would
 * result in broken rendering of GLES apps that aren't expecting sRGB encode.
 *
 * Unfortunately, renderbuffer setup happens before a context is created.  So
 * in intel_screen.c we always set up sRGB, and here, if you're a GLES2/3
 * context (without an sRGB visual, though we don't have sRGB visuals exposed
 * yet), we go turn that back off before anyone finds out.
 */
static void
intel_gles3_srgb_workaround(struct brw_context *brw,
                            struct gl_framebuffer *fb)
{
   struct gl_context *ctx = &brw->ctx;

   if (_mesa_is_desktop_gl(ctx) || !fb->Visual.sRGBCapable)
      return;

   /* Some day when we support the sRGB capable bit on visuals available for
    * GLES, we'll need to respect that and not disable things here.
    */
   fb->Visual.sRGBCapable = false;
   for (int i = 0; i < BUFFER_COUNT; i++) {
      if (fb->Attachment[i].Renderbuffer &&
          fb->Attachment[i].Renderbuffer->Format == MESA_FORMAT_SARGB8) {
         fb->Attachment[i].Renderbuffer->Format = MESA_FORMAT_ARGB8888;
      }
   }
}

GLboolean
intelMakeCurrent(__DRIcontext * driContextPriv,
                 __DRIdrawable * driDrawPriv,
                 __DRIdrawable * driReadPriv)
{
   struct brw_context *brw;
   GET_CURRENT_CONTEXT(curCtx);

   if (driContextPriv)
      brw = (struct brw_context *) driContextPriv->driverPrivate;
   else
      brw = NULL;

   /* According to the glXMakeCurrent() man page: "Pending commands to
    * the previous context, if any, are flushed before it is released."
    * But only flush if we're actually changing contexts.
    */
   if (brw_context(curCtx) && brw_context(curCtx) != brw) {
      _mesa_flush(curCtx);
   }

   if (driContextPriv) {
      struct gl_context *ctx = &brw->ctx;
      struct gl_framebuffer *fb, *readFb;
      
      if (driDrawPriv == NULL && driReadPriv == NULL) {
         fb = _mesa_get_incomplete_framebuffer();
         readFb = _mesa_get_incomplete_framebuffer();
      } else {
         fb = driDrawPriv->driverPrivate;
         readFb = driReadPriv->driverPrivate;
         driContextPriv->dri2.draw_stamp = driDrawPriv->dri2.stamp - 1;
         driContextPriv->dri2.read_stamp = driReadPriv->dri2.stamp - 1;
      }

      /* The sRGB workaround changes the renderbuffer's format. We must change
       * the format before the renderbuffer's miptree get's allocated, otherwise
       * the formats of the renderbuffer and its miptree will differ.
       */
      intel_gles3_srgb_workaround(brw, fb);
      intel_gles3_srgb_workaround(brw, readFb);

      intel_prepare_render(brw);
      _mesa_make_current(ctx, fb, readFb);
   }
   else {
      _mesa_make_current(NULL, NULL, NULL);
   }

   return true;
}

/**
 * \brief Query DRI2 to obtain a DRIdrawable's buffers.
 *
 * To determine which DRI buffers to request, examine the renderbuffers
 * attached to the drawable's framebuffer. Then request the buffers with
 * DRI2GetBuffers() or DRI2GetBuffersWithFormat().
 *
 * This is called from intel_update_renderbuffers().
 *
 * \param drawable      Drawable whose buffers are queried.
 * \param buffers       [out] List of buffers returned by DRI2 query.
 * \param buffer_count  [out] Number of buffers returned.
 *
 * \see intel_update_renderbuffers()
 * \see DRI2GetBuffers()
 * \see DRI2GetBuffersWithFormat()
 */
static void
intel_query_dri2_buffers(struct brw_context *brw,
                         __DRIdrawable *drawable,
                         __DRIbuffer **buffers,
                         int *buffer_count)
{
   __DRIscreen *screen = brw->intelScreen->driScrnPriv;
   struct gl_framebuffer *fb = drawable->driverPrivate;
   int i = 0;
   unsigned attachments[8];

   struct intel_renderbuffer *front_rb;
   struct intel_renderbuffer *back_rb;

   front_rb = intel_get_renderbuffer(fb, BUFFER_FRONT_LEFT);
   back_rb = intel_get_renderbuffer(fb, BUFFER_BACK_LEFT);

   memset(attachments, 0, sizeof(attachments));
   if ((brw->is_front_buffer_rendering ||
        brw->is_front_buffer_reading ||
        !back_rb) && front_rb) {
      /* If a fake front buffer is in use, then querying for
       * __DRI_BUFFER_FRONT_LEFT will cause the server to copy the image from
       * the real front buffer to the fake front buffer.  So before doing the
       * query, we need to make sure all the pending drawing has landed in the
       * real front buffer.
       */
      intel_batchbuffer_flush(brw);
      intel_flush_front(&brw->ctx);

      attachments[i++] = __DRI_BUFFER_FRONT_LEFT;
      attachments[i++] = intel_bits_per_pixel(front_rb);
   } else if (front_rb && brw->front_buffer_dirty) {
      /* We have pending front buffer rendering, but we aren't querying for a
       * front buffer.  If the front buffer we have is a fake front buffer,
       * the X server is going to throw it away when it processes the query.
       * So before doing the query, make sure all the pending drawing has
       * landed in the real front buffer.
       */
      intel_batchbuffer_flush(brw);
      intel_flush_front(&brw->ctx);
   }

   if (back_rb) {
      attachments[i++] = __DRI_BUFFER_BACK_LEFT;
      attachments[i++] = intel_bits_per_pixel(back_rb);
   }

   assert(i <= ARRAY_SIZE(attachments));

   *buffers = screen->dri2.loader->getBuffersWithFormat(drawable,
                                                        &drawable->w,
                                                        &drawable->h,
                                                        attachments, i / 2,
                                                        buffer_count,
                                                        drawable->loaderPrivate);
}

/**
 * \brief Assign a DRI buffer's DRM region to a renderbuffer.
 *
 * This is called from intel_update_renderbuffers().
 *
 * \par Note:
 *    DRI buffers whose attachment point is DRI2BufferStencil or
 *    DRI2BufferDepthStencil are handled as special cases.
 *
 * \param buffer_name is a human readable name, such as "dri2 front buffer",
 *        that is passed to intel_region_alloc_for_handle().
 *
 * \see intel_update_renderbuffers()
 * \see intel_region_alloc_for_handle()
 */
static void
intel_process_dri2_buffer(struct brw_context *brw,
                          __DRIdrawable *drawable,
                          __DRIbuffer *buffer,
                          struct intel_renderbuffer *rb,
                          const char *buffer_name)
{
   struct intel_region *region = NULL;

   if (!rb)
      return;

   unsigned num_samples = rb->Base.Base.NumSamples;

   /* We try to avoid closing and reopening the same BO name, because the first
    * use of a mapping of the buffer involves a bunch of page faulting which is
    * moderately expensive.
    */
   if (num_samples == 0) {
       if (rb->mt &&
           rb->mt->region &&
           rb->mt->region->name == buffer->name)
          return;
   } else {
       if (rb->mt &&
           rb->mt->singlesample_mt &&
           rb->mt->singlesample_mt->region &&
           rb->mt->singlesample_mt->region->name == buffer->name)
          return;
   }

   if (unlikely(INTEL_DEBUG & DEBUG_DRI)) {
      fprintf(stderr,
              "attaching buffer %d, at %d, cpp %d, pitch %d\n",
              buffer->name, buffer->attachment,
              buffer->cpp, buffer->pitch);
   }

   intel_miptree_release(&rb->mt);
   region = intel_region_alloc_for_handle(brw->intelScreen,
                                          buffer->cpp,
                                          drawable->w,
                                          drawable->h,
                                          buffer->pitch,
                                          buffer->name,
                                          buffer_name);
   if (!region)
      return;

   rb->mt = intel_miptree_create_for_dri2_buffer(brw,
                                                 buffer->attachment,
                                                 intel_rb_format(rb),
                                                 num_samples,
                                                 region);
   intel_region_release(&region);
}