Revert "avutils/hwcontext: When deriving a hwdevice, search for existing device in both directions"

This reverts commit a428949775.
There were objections on ML (see
https://ffmpeg.org/pipermail/ffmpeg-devel/2021-December/290530.html)

Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>

libavutil/hwcontext.c

@@ -122,7 +122,6 @@ static const AVClass hwdevice_ctx_class = {
 static void hwdevice_ctx_free(void *opaque, uint8_t *data)
 {
     AVHWDeviceContext *ctx = (AVHWDeviceContext*)data;
-    int i;
 
     /* uninit might still want access the hw context and the user
      * free() callback might destroy it, so uninit has to be called first */
@@ -133,8 +132,6 @@ static void hwdevice_ctx_free(void *opaque, uint8_t *data)
         ctx->free(ctx);
 
     av_buffer_unref(&ctx->internal->source_device);
-    for (i = 0; i < AV_HWDEVICE_TYPE_NB; i++)
-        av_buffer_unref(&ctx->internal->derived_devices[i]);
 
     av_freep(&ctx->hwctx);
     av_freep(&ctx->internal->priv);
@@ -646,26 +643,6 @@ fail:
     return ret;
 }
 
-static AVBufferRef* find_derived_hwdevice_ctx(AVBufferRef *src_ref, enum AVHWDeviceType type)
-{
-    AVBufferRef *tmp_ref;
-    AVHWDeviceContext *src_ctx;
-    int i;
-
-    src_ctx = (AVHWDeviceContext*)src_ref->data;
-    if (src_ctx->type == type)
-        return src_ref;
-
-    for (i = 0; i < AV_HWDEVICE_TYPE_NB; i++)
-        if (src_ctx->internal->derived_devices[i]) {
-            tmp_ref = find_derived_hwdevice_ctx(src_ctx->internal->derived_devices[i], type);
-            if (tmp_ref)
-                return tmp_ref;
-        }
-
-    return NULL;
-}
-
 int av_hwdevice_ctx_create_derived_opts(AVBufferRef **dst_ref_ptr,
                                         enum AVHWDeviceType type,
                                         AVBufferRef *src_ref,
@@ -689,16 +666,6 @@ int av_hwdevice_ctx_create_derived_opts(AVBufferRef **dst_ref_ptr,
         tmp_ref = tmp_ctx->internal->source_device;
     }
 
-    tmp_ref = find_derived_hwdevice_ctx(src_ref, type);
-    if (tmp_ref) {
-        dst_ref = av_buffer_ref(tmp_ref);
-        if (!dst_ref) {
-            ret = AVERROR(ENOMEM);
-            goto fail;
-        }
-        goto done;
-    }
-
     dst_ref = av_hwdevice_ctx_alloc(type);
     if (!dst_ref) {
         ret = AVERROR(ENOMEM);
@@ -720,11 +687,6 @@ int av_hwdevice_ctx_create_derived_opts(AVBufferRef **dst_ref_ptr,
                     ret = AVERROR(ENOMEM);
                     goto fail;
                 }
-                tmp_ctx->internal->derived_devices[type] = av_buffer_ref(dst_ref);
-                if (!tmp_ctx->internal->derived_devices[type]) {
-                    ret = AVERROR(ENOMEM);
-                    goto fail;
-                }
                 ret = av_hwdevice_ctx_init(dst_ref);
                 if (ret < 0)
                     goto fail;

libavutil/hwcontext.h

@@ -37,7 +37,6 @@ enum AVHWDeviceType {
     AV_HWDEVICE_TYPE_OPENCL,
     AV_HWDEVICE_TYPE_MEDIACODEC,
     AV_HWDEVICE_TYPE_VULKAN,
-    AV_HWDEVICE_TYPE_NB,          ///< number of hw device types, not part of API/ABI.
 };
 
 typedef struct AVHWDeviceInternal AVHWDeviceInternal;

libavutil/hwcontext_internal.h

@@ -109,12 +109,6 @@ struct AVHWDeviceInternal {
      * context it was derived from.
      */
     AVBufferRef *source_device;
-
-    /**
-     * An array of reference to device contexts which
-     * were derived from this device.
-     */
-    AVBufferRef *derived_devices[AV_HWDEVICE_TYPE_NB];
 };
 
 struct AVHWFramesInternal {

libavutil/hwcontext_qsv.c

@@ -274,7 +274,7 @@ static void qsv_frames_uninit(AVHWFramesContext *ctx)
     av_buffer_unref(&s->child_frames_ref);
 }
 
-static void qsv_release_dummy(void *opaque, uint8_t *data)
+static void qsv_pool_release_dummy(void *opaque, uint8_t *data)
 {
 }
 
@@ -287,7 +287,7 @@ static AVBufferRef *qsv_pool_alloc(void *opaque, size_t size)
     if (s->nb_surfaces_used < hwctx->nb_surfaces) {
         s->nb_surfaces_used++;
         return av_buffer_create((uint8_t*)(s->surfaces_internal + s->nb_surfaces_used - 1),
-                                sizeof(*hwctx->surfaces), qsv_release_dummy, NULL, 0);
+                                sizeof(*hwctx->surfaces), qsv_pool_release_dummy, NULL, 0);
     }
 
     return NULL;
@@ -1596,15 +1596,8 @@ static int qsv_device_create(AVHWDeviceContext *ctx, const char *device,
     child_device = (AVHWDeviceContext*)priv->child_device_ctx->data;
 
     impl = choose_implementation(device, child_device_type);
-    ret = qsv_device_derive_from_child(ctx, impl, child_device, 0);
-    if (ret >= 0) {
-        ctx->internal->source_device = av_buffer_ref(priv->child_device_ctx);
-        child_device->internal->derived_devices[ctx->type] = av_buffer_create((uint8_t*)ctx, sizeof(*ctx), qsv_release_dummy, ctx, 0);
-        if (!child_device->internal->derived_devices[ctx->type])
-            return AVERROR(ENOMEM);
-    }
 
-    return ret;
+    return qsv_device_derive_from_child(ctx, impl, child_device, 0);
 }
 
 const HWContextType ff_hwcontext_type_qsv = {