glx: Import glxvnd server module (v2)

This is based on an out-of-tree module written by Kyle:

https://github.com/kbrenneman/libglvnd/tree/server-libglx

I (ajax) did a bunch of cosmetic fixes, ported it off xfree86 API,
added request length checks, and fixed a minor bug or two.

v2: Use separate functions to set/get a context tag's private data, and
call the backend's MakeCurrent when a client disconnects to unbind the
context. (Kyle Brenneman)

Signed-off-by: Adam Jackson <ajax@redhat.com>

glx/vndservervendor.c

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2016, NVIDIA CORPORATION.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and/or associated documentation files (the
+ * "Materials"), to deal in the Materials without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Materials, and to
+ * permit persons to whom the Materials are furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * unaltered in all copies or substantial portions of the Materials.
+ * Any additions, deletions, or changes to the original source files
+ * must be clearly indicated in accompanying documentation.
+ *
+ * If only executable code is distributed, then the accompanying
+ * documentation must state that "this software is based in part on the
+ * work of the Khronos Group."
+ *
+ * THE MATERIALS ARE 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 NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 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
+ * MATERIALS OR THE USE OR OTHER DEALINGS IN THE MATERIALS.
+ */
+
+#include "vndservervendor.h"
+
+struct xorg_list GlxVendorList = { &GlxVendorList, &GlxVendorList };
+
+GlxServerVendor *GlxCreateVendor(const GlxServerImports *imports)
+{
+    GlxServerVendor *vendor = NULL;
+
+    if (imports == NULL) {
+        ErrorF("GLX: Vendor library did not provide an imports table\n");
+        return NULL;
+    }
+
+    if (imports->extensionCloseDown == NULL
+            || imports->handleRequest == NULL
+            || imports->getDispatchAddress == NULL
+            || imports->makeCurrent == NULL) {
+        ErrorF("GLX: Vendor library is missing required callback functions.\n");
+        return NULL;
+    }
+
+    vendor = (GlxServerVendor *) calloc(1, sizeof(GlxServerVendor));
+    if (vendor == NULL) {
+        ErrorF("GLX: Can't allocate vendor library.\n");
+        return NULL;
+    }
+    memcpy(&vendor->glxvc, imports, sizeof(GlxServerImports));
+
+    xorg_list_append(&vendor->entry, &GlxVendorList);
+    return vendor;
+}
+
+void GlxDestroyVendor(GlxServerVendor *vendor)
+{
+    if (vendor != NULL) {
+        xorg_list_del(&vendor->entry);
+        free(vendor);
+    }
+}
+
+void GlxVendorExtensionReset(const ExtensionEntry *extEntry)
+{
+    GlxServerVendor *vendor, *tempVendor;
+
+    // TODO: Do we allow the driver to destroy a vendor library handle from
+    // here?
+    xorg_list_for_each_entry_safe(vendor, tempVendor, &GlxVendorList, entry) {
+        if (vendor->glxvc.extensionCloseDown != NULL) {
+            vendor->glxvc.extensionCloseDown(extEntry);
+        }
+    }
+
+    // If the server is exiting instead of starting a new generation, then
+    // free the remaining GlxServerVendor structs.
+    //
+    // XXX this used to be conditional on xf86ServerIsExiting, but it's
+    // cleaner to just always create the vendor struct on every generation,
+    // if nothing else so all ddxes get the same behavior.
+    xorg_list_for_each_entry_safe(vendor, tempVendor, &GlxVendorList, entry) {
+        GlxDestroyVendor(vendor);
+    }
+}