avutil/hwcontext_cuda: add option to use primary device context

doc/ffmpeg.texi

@@ -1096,6 +1096,21 @@ device type:
 @item cuda
 @var{device} is the number of the CUDA device.
 
+The following options are recognized:
+@table @option
+@item primary_ctx
+If set to 1, uses the primary device context instead of creating a new one.
+@end table
+
+Examples:
+@table @emph
+@item -init_hw_device cuda:1
+Choose the second device on the system.
+
+@item -init_hw_device cuda:0,primary_ctx=1
+Choose the first device and use the primary device context.
+@end table
+
 @item dxva2
 @var{device} is the number of the Direct3D 9 display adapter.
 

libavutil/hwcontext_cuda.c

@@ -376,6 +376,22 @@ static int cuda_context_init(AVHWDeviceContext *device_ctx, int flags) {
     return 0;
 }
 
+static int cuda_flags_from_opts(AVHWDeviceContext *device_ctx,
+                                AVDictionary *opts, int *flags)
+{
+    AVDictionaryEntry *primary_ctx_opt = av_dict_get(opts, "primary_ctx", NULL, 0);
+
+    if (primary_ctx_opt && strtol(primary_ctx_opt->value, NULL, 10)) {
+        av_log(device_ctx, AV_LOG_VERBOSE, "Using CUDA primary device context\n");
+        *flags |= AV_CUDA_USE_PRIMARY_CONTEXT;
+    } else if (primary_ctx_opt) {
+        av_log(device_ctx, AV_LOG_VERBOSE, "Disabling use of CUDA primary device context\n");
+        *flags &= ~AV_CUDA_USE_PRIMARY_CONTEXT;
+    }
+
+    return 0;
+}
+
 static int cuda_device_create(AVHWDeviceContext *device_ctx,
                               const char *device,
                               AVDictionary *opts, int flags)
@@ -384,6 +400,10 @@ static int cuda_device_create(AVHWDeviceContext *device_ctx,
     CudaFunctions *cu;
     int ret, device_idx = 0;
 
+    ret = cuda_flags_from_opts(device_ctx, opts, &flags);
+    if (ret < 0)
+        return ret;
+
     if (device)
         device_idx = strtol(device, NULL, 0);
 
@@ -419,6 +439,10 @@ static int cuda_device_derive(AVHWDeviceContext *device_ctx,
     const char *src_uuid = NULL;
     int ret, i, device_count;
 
+    ret = cuda_flags_from_opts(device_ctx, opts, &flags);
+    if (ret < 0)
+        return ret;
+
 #if CONFIG_VULKAN
     VkPhysicalDeviceIDProperties vk_idp = {
         .sType = VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_ID_PROPERTIES,

libavutil/version.h

@@ -80,7 +80,7 @@
 
 #define LIBAVUTIL_VERSION_MAJOR  57
 #define LIBAVUTIL_VERSION_MINOR   9
-#define LIBAVUTIL_VERSION_MICRO 100
+#define LIBAVUTIL_VERSION_MICRO 101
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
                                                LIBAVUTIL_VERSION_MINOR, \