hwcontext_cuda: implement frames_get_constraints

Copied and modified from hwcontext_qsv.c.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavutil/hwcontext_cuda.c

@@ -37,6 +37,31 @@ static const enum AVPixelFormat supported_formats[] = {
     AV_PIX_FMT_YUV444P16,
 };
 
+static int cuda_frames_get_constraints(AVHWDeviceContext *ctx,
+                                       const void *hwconfig,
+                                       AVHWFramesConstraints *constraints)
+{
+    int i;
+
+    constraints->valid_sw_formats = av_malloc_array(FF_ARRAY_ELEMS(supported_formats) + 1,
+                                                    sizeof(*constraints->valid_sw_formats));
+    if (!constraints->valid_sw_formats)
+        return AVERROR(ENOMEM);
+
+    for (i = 0; i < FF_ARRAY_ELEMS(supported_formats); i++)
+        constraints->valid_sw_formats[i] = supported_formats[i];
+    constraints->valid_sw_formats[FF_ARRAY_ELEMS(supported_formats)] = AV_PIX_FMT_NONE;
+
+    constraints->valid_hw_formats = av_malloc_array(2, sizeof(*constraints->valid_hw_formats));
+    if (!constraints->valid_hw_formats)
+        return AVERROR(ENOMEM);
+
+    constraints->valid_hw_formats[0] = AV_PIX_FMT_CUDA;
+    constraints->valid_hw_formats[1] = AV_PIX_FMT_NONE;
+
+    return 0;
+}
+
 static void cuda_buffer_free(void *opaque, uint8_t *data)
 {
     AVHWFramesContext *ctx = opaque;
@@ -326,6 +351,7 @@ const HWContextType ff_hwcontext_type_cuda = {
     .frames_priv_size     = sizeof(CUDAFramesContext),
 
     .device_create        = cuda_device_create,
+    .frames_get_constraints = cuda_frames_get_constraints,
     .frames_init          = cuda_frames_init,
     .frames_get_buffer    = cuda_get_buffer,
     .transfer_get_formats = cuda_transfer_get_formats,