diff options
| -rw-r--r-- | src/mesa/drivers/dri/intel/intel_screen.h | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/src/mesa/drivers/dri/intel/intel_screen.h b/src/mesa/drivers/dri/intel/intel_screen.h index 4613c9858c4..5d13dfba612 100644 --- a/src/mesa/drivers/dri/intel/intel_screen.h +++ b/src/mesa/drivers/dri/intel/intel_screen.h @@ -34,6 +34,62 @@ #include "i915_drm.h" #include "xmlconfig.h" +/** + * \brief Does X driver support DRI2BufferHiz and DRI2BufferStencil? + * + * (Here, "X driver" referes to the DDX driver, xf86-video-intel). + * + * The DRI2 protocol does not allow us to query the X driver's version nor + * query for a list of buffer formats that the driver supports. So, to + * determine if the X driver supports DRI2BufferHiz and DRI2BufferStencil we + * must resort to a handshake. + * + * If the hardware lacks support for separate stencil (and consequently, lacks + * support for hiz also), then the X driver's separate stencil and hiz support + * is irrelevant and the handshake never occurs. + * + * Complications + * ------------- + * The handshake is complicated by a bug in xf86-video-intel 2.15. Even though + * that version of the X driver did not supppot requests for DRI2BufferHiz or + * DRI2BufferStencil, if requested one it still allocated and returned one. + * The returned buffer, however, was incorrectly X tiled. + * + * How the handshake works + * ----------------------- + * (TODO: To be implemented on a future commit). + * + * Initially, intel_screen.dri2_has_hiz is set to unknown. The first time the + * user requests a depth and stencil buffer, intelCreateBuffers() creates a + * framebuffer with separate depth and stencil attachments (with formats + * x8_z24 and s8). + * + * Eventually, intel_update_renderbuffers() makes a DRI2 request for + * DRI2BufferStencil and DRI2BufferHiz. If the returned buffers are Y tiled, + * then we joyfully set intel_screen.dri2_has_hiz to true and continue as if + * nothing happend. + * + * If the buffers are X tiled, however, the handshake has failed and we must + * clean up. + * 1. Angrily set intel_screen.dri2_has_hiz to false. + * 2. Discard the framebuffer's depth and stencil attachments. + * 3. Attach a packed depth/stencil buffer to the framebuffer (with format + * s8_z24). + * 4. Make a DRI2 request for the new buffer, using attachment type + * DRI2BufferDepthStencil). + * + * Future Considerations + * --------------------- + * On a sunny day in the far future, when we are certain that no one has an + * xf86-video-intel installed without hiz and separate stencil support, then + * this enumerant and the handshake should die. + */ +enum intel_dri2_has_hiz { + INTEL_DRI2_HAS_HIZ_UNKNOWN, + INTEL_DRI2_HAS_HIZ_TRUE, + INTEL_DRI2_HAS_HIZ_FALSE, +}; + struct intel_screen { int deviceID; |