glx/dri2: Add support for GLX_ARB_create_context_robustness

Add the infrastructure required for this extension.  There is no
xserver support and no driver support yet.  Drivers can enable this be
advertising DRI2 version 4 and accepting the
__DRI_CTX_FLAG_ROBUST_BUFFER_ACCESS flag and the
__DRI_CTX_ATTRIB_RESET_STRATEGY attribute in create context.

Some additional Mesa infrastructure is needed before drivers can do
this.  The GL_ARB_robustness spec, which all Mesa drivers already
advertise, requires:

    "If the behavior is LOSE_CONTEXT_ON_RESET_ARB, a graphics reset
    will result in the loss of all context state, requiring the
    recreation of all associated objects."

It is necessary to land this infrastructure now so that the related
infrastructure can land in the xserver.  The xserver has very long
release schedules, and the remaining Mesa parts should land long, long
before the next xserver merge window opens.

v2: Expose robustness as a DRI2 extension rather than bumping
__DRI_DRI2_VERSION.

v3: Add a comment explaining why dri2->base.version >= 3 is also
required for GLX_ARB_create_context_robustness.

Signed-off-by: Ian Romanick <[email protected]>
Reviewed-by: Kenneth Graunke <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

1 files changed, 21 insertions, 2 deletions

diff --git a/src/glx/dri2_glx.c b/src/glx/dri2_glx.c
index b6988c3ca60..79237c3c91b 100644
--- a/src/glx/dri2_glx.c
+++ b/src/glx/dri2_glx.c
@@ -241,7 +241,8 @@ dri2_create_context_attribs(struct glx_screen *base,
    uint32_t major_ver = 2;
    uint32_t flags = 0;
    unsigned api;
-   uint32_t ctx_attribs[2 * 4];
+   int reset;
+   uint32_t ctx_attribs[2 * 5];
    unsigned num_ctx_attribs = 0;
 
    if (psc->dri2->base.version < 3) {
@@ -252,7 +253,8 @@ dri2_create_context_attribs(struct glx_screen *base,
    /* Remap the GLX tokens to DRI2 tokens.
     */
    if (!dri2_convert_glx_attribs(num_attribs, attribs,
-				 &major_ver, &minor_ver, &flags, &api, error))
+				 &major_ver, &minor_ver, &flags, &api, &reset,
+                                 error))
       goto error_exit;
 
    if (shareList) {
@@ -275,6 +277,15 @@ dri2_create_context_attribs(struct glx_screen *base,
    ctx_attribs[num_ctx_attribs++] = __DRI_CTX_ATTRIB_MINOR_VERSION;
    ctx_attribs[num_ctx_attribs++] = minor_ver;
 
+   /* Only send a value when the non-default value is requested.  By doing
+    * this we don't have to check the driver's DRI2 version before sending the
+    * default value.
+    */
+   if (reset != __DRI_CTX_RESET_NO_NOTIFICATION) {
+      ctx_attribs[num_ctx_attribs++] = __DRI_CTX_ATTRIB_RESET_STRATEGY;
+      ctx_attribs[num_ctx_attribs++] = reset;
+   }
+
    if (flags != 0) {
       ctx_attribs[num_ctx_attribs++] = __DRI_CTX_ATTRIB_FLAGS;
 
@@ -979,6 +990,14 @@ dri2BindExtensions(struct dri2_screen *psc, const __DRIextension **extensions)
 
       if (((strcmp(extensions[i]->name, __DRI2_THROTTLE) == 0)))
 	 psc->throttle = (__DRI2throttleExtension *) extensions[i];
+
+      /* DRI2 version 3 is also required because
+       * GLX_ARB_create_context_robustness requires GLX_ARB_create_context.
+       */
+      if (psc->dri2->base.version >= 3
+          && strcmp(extensions[i]->name, __DRI2_ROBUSTNESS) == 0)
+         __glXEnableDirectExtension(&psc->base,
+                                    "GLX_ARB_create_context_robustness");
    }
 }