avcodec/nvenc: add logging for more error cases

libavcodec/nvenc.c

@@ -325,12 +325,16 @@ static av_cold int nvenc_check_device(AVCodecContext *avctx, int idx)
     }
 
     cu_res = dl_fn->cuda_dl->cuDeviceGetName(name, sizeof(name), cu_device);
-    if (cu_res != CUDA_SUCCESS)
+    if (cu_res != CUDA_SUCCESS) {
+        av_log(avctx, AV_LOG_ERROR, "cuDeviceGetName failed on device %d\n", idx);
         return -1;
+    }
 
     cu_res = dl_fn->cuda_dl->cuDeviceComputeCapability(&major, &minor, cu_device);
-    if (cu_res != CUDA_SUCCESS)
+    if (cu_res != CUDA_SUCCESS) {
+        av_log(avctx, AV_LOG_ERROR, "cuDeviceComputeCapability failed on device %d\n", idx);
         return -1;
+    }
 
     av_log(avctx, loglevel, "[ GPU #%d - < %s > has Compute SM %d.%d ]\n", idx, name, major, minor);
     if (((major << 4) | minor) < NVENC_CAP) {