dri: Implement a DRI vtable extension to replace the global driDriverAPI.

As we move to megadrivers, we are unable to build multiple drivers with
the same public global symbol per driver (Think an X Server with an intel
and a nouveau driver, and the X Server implementing indirect for both --
we have to actually talk to the right driver).  By slipping the
driDriverAPI vtable into the driver's extension list, we can replace the
usage of the global symbol with usage of the loader-dlsym()ed driver
information.

v2: Pull in the hunk to avoid crashing on null driver_extensions.  Thanks,
    Emil!

Reviewed-by: Matt Turner <mattst88@gmail.com> (v1)
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>

diff --git a/include/GL/internal/dri_interface.h b/include/GL/internal/dri_interface.h
index a7afa22466450b347a2ac8e3c2467e571cbb4bf6..48993b93930f316372b8773bf86e5e2ccd5aa339 100644 (file)
--- a/include/GL/internal/dri_interface.h
+++ b/include/GL/internal/dri_interface.h
@@ -1270,4 +1270,21 @@ typedef struct __DRIconfigOptionsExtensionRec {
    const char *xml;
 } __DRIconfigOptionsExtension;
 
+/**
+ * This extension provides a driver vtable to a set of common driver helper
+ * functions (driCoreExtension, driDRI2Extension) within the driver
+ * implementation, as opposed to having to pass them through a global
+ * variable.
+ *
+ * It is not intended to be public API to the actual loader, and the vtable
+ * layout may change at any time.
+ */
+#define __DRI_DRIVER_VTABLE "DRI_DriverVtable"
+#define __DRI_DRIVER_VTABLE_VERSION 1
+
+typedef struct __DRIDriverVtableExtensionRec {
+    __DRIextension base;
+    const struct __DriverAPIRec *vtable;
+} __DRIDriverVtableExtension;
+
 #endif

diff --git a/src/mesa/drivers/dri/common/dri_util.c b/src/mesa/drivers/dri/common/dri_util.c
index 8a413daf043d5a0733e3744992b9a016e839b5c7..2a85703f2ad09674c1e976b081672970e166126b 100644 (file)
--- a/src/mesa/drivers/dri/common/dri_util.c
+++ b/src/mesa/drivers/dri/common/dri_util.c
@@ -101,8 +101,21 @@ dri2CreateNewScreen2(int scrn, int fd,
     if (!psp)
        return NULL;
 
+    /* By default, use the global driDriverAPI symbol (non-megadrivers). */
     psp->driver = &driDriverAPI;
 
+    /* If the driver exposes its vtable through its extensions list
+     * (megadrivers), use that instead.
+     */
+    if (driver_extensions) {
+       for (int i = 0; driver_extensions[i]; i++) {
+          if (strcmp(driver_extensions[i]->name, __DRI_DRIVER_VTABLE) == 0) {
+             psp->driver =
+                ((__DRIDriverVtableExtension *)driver_extensions[i])->vtable;
+          }
+       }
+    }
+
     setupLoaderExtensions(psp, extensions);
 
 #ifndef __NOT_HAVE_DRM_H