avutil/hwcontext_d3d12va: Allocate pub and priv device hwctx together

This is possible because the lifetime of both coincide.
Besides reducing the number of allocations this also simplifies
access to D3D12VADevicePriv as one no longer has to
go through AVHWDeviceInternal.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavutil/hwcontext_d3d12va.c

@@ -46,6 +46,10 @@ typedef struct D3D12VAFramesContext {
 } D3D12VAFramesContext;
 
 typedef struct D3D12VADevicePriv {
+    /**
+     * The public AVD3D12VADeviceContext. See hwcontext_d3d12va.h for it.
+     */
+    AVD3D12VADeviceContext p;
     HANDLE                        d3d12lib;
     HANDLE                        dxgilib;
     PFN_CREATE_DXGI_FACTORY2      create_dxgi_factory2;
@@ -526,7 +530,7 @@ fail:
 
 static int d3d12va_load_functions(AVHWDeviceContext *hwdev)
 {
-    D3D12VADevicePriv *priv = hwdev->internal->priv;
+    D3D12VADevicePriv *priv = hwdev->hwctx;
 
 #if !HAVE_UWP
     priv->d3d12lib = dlopen("d3d12.dll", 0);
@@ -558,8 +562,8 @@ fail:
 
 static void d3d12va_device_free(AVHWDeviceContext *hwdev)
 {
-    AVD3D12VADeviceContext *ctx  = hwdev->hwctx;
-    D3D12VADevicePriv      *priv = hwdev->internal->priv;
+    D3D12VADevicePriv      *priv = hwdev->hwctx;
+    AVD3D12VADeviceContext *ctx  = &priv->p;
 
     D3D12_OBJECT_RELEASE(ctx->device);
 
@@ -609,8 +613,8 @@ static void d3d12va_device_uninit(AVHWDeviceContext *hwdev)
 static int d3d12va_device_create(AVHWDeviceContext *hwdev, const char *device,
                                  AVDictionary *opts, int flags)
 {
-    AVD3D12VADeviceContext *ctx  = hwdev->hwctx;
-    D3D12VADevicePriv      *priv = hwdev->internal->priv;
+    D3D12VADevicePriv      *priv = hwdev->hwctx;
+    AVD3D12VADeviceContext *ctx  = &priv->p;
 
     HRESULT hr;
     UINT create_flags = 0;
@@ -670,8 +674,7 @@ const HWContextType ff_hwcontext_type_d3d12va = {
     .type                   = AV_HWDEVICE_TYPE_D3D12VA,
     .name                   = "D3D12VA",
 
-    .device_hwctx_size      = sizeof(AVD3D12VADeviceContext),
-    .device_priv_size       = sizeof(D3D12VADevicePriv),
+    .device_hwctx_size      = sizeof(D3D12VADevicePriv),
     .frames_hwctx_size      = sizeof(AVD3D12VAFramesContext),
     .frames_priv_size       = sizeof(D3D12VAFramesContext),