main: Use a derived value for the default sample count

Previously the framebuffer default sample count was taken directly
from the value given by the application. On the i965 driver on HSW if
the value wasn't one that is supported by the hardware it would hit an
assert when it tried to program the state for it. This patch fixes it
by adding a derived sample count to the state for the default
framebuffer. The driver can then quantize this to one of the valid
values in its UpdateState handler when the _NEW_BUFFERS state changes.
_mesa_geometric_samples is changed to use the new derived value.

Fixes the piglit test arb_framebuffer_no_attachments-query

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93957
Cc: Ilia Mirkin <[email protected]>
Reviewed-by: Ilia Mirkin <[email protected]>

3 files changed, 25 insertions, 1 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
index 1032e5a8175..44d2fe4d9e4 100644
--- a/src/mesa/drivers/dri/i965/brw_context.c
+++ b/src/mesa/drivers/dri/i965/brw_context.c
@@ -167,6 +167,19 @@ intel_viewport(struct gl_context *ctx)
 }
 
 static void
+intel_update_framebuffer(struct gl_context *ctx,
+                         struct gl_framebuffer *fb)
+{
+   struct brw_context *brw = brw_context(ctx);
+
+   /* Quantize the derived default number of samples
+    */
+   fb->DefaultGeometry._NumSamples =
+      intel_quantize_num_samples(brw->intelScreen,
+                                 fb->DefaultGeometry.NumSamples);
+}
+
+static void
 intel_update_state(struct gl_context * ctx, GLuint new_state)
 {
    struct brw_context *brw = brw_context(ctx);
@@ -245,6 +258,12 @@ intel_update_state(struct gl_context * ctx, GLuint new_state)
    }
 
    _mesa_lock_context_textures(ctx);
+
+   if (new_state & _NEW_BUFFERS) {
+      intel_update_framebuffer(ctx, ctx->DrawBuffer);
+      if (ctx->DrawBuffer != ctx->ReadBuffer)
+         intel_update_framebuffer(ctx, ctx->ReadBuffer);
+   }
 }
 
 #define flushFront(screen)      ((screen)->image.loader ? (screen)->image.loader->flushFrontBuffer : (screen)->dri2.loader->flushFrontBuffer)
diff --git a/src/mesa/main/framebuffer.h b/src/mesa/main/framebuffer.h
index ab077ed9f49..fa434d447ae 100644
--- a/src/mesa/main/framebuffer.h
+++ b/src/mesa/main/framebuffer.h
@@ -97,7 +97,8 @@ static inline GLuint
 _mesa_geometric_samples(const struct gl_framebuffer *buffer)
 {
    return buffer->_HasAttachments ?
-      buffer->Visual.samples : buffer->DefaultGeometry.NumSamples;
+      buffer->Visual.samples :
+      buffer->DefaultGeometry._NumSamples;
 }
 
 static inline GLuint
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 0a42bfb814d..258fb3f2aef 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -3223,6 +3223,10 @@ struct gl_framebuffer
    struct {
      GLuint Width, Height, Layers, NumSamples;
      GLboolean FixedSampleLocations;
+     /* Derived from NumSamples by the driver so that it can choose a valid
+      * value for the hardware.
+      */
+     GLuint _NumSamples;
    } DefaultGeometry;
 
    /** \name  Drawing bounds (Intersection of buffer size and scissor box)