[media] uvcvideo: Don't fail when an unsupported format is requested

Return the default format in that case.
This issue was found by the v4l2-compliance tool.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/usb/uvc/uvc_v4l2.c

@@ -165,17 +165,18 @@ static int uvc_v4l2_try_format(struct uvc_streaming *stream,
 			fcc[0], fcc[1], fcc[2], fcc[3],
 			fmt->fmt.pix.width, fmt->fmt.pix.height);
 
-	/* Check if the hardware supports the requested format. */
+	/* Check if the hardware supports the requested format, use the default
+	 * format otherwise.
+	 */
 	for (i = 0; i < stream->nformats; ++i) {
 		format = &stream->format[i];
 		if (format->fcc == fmt->fmt.pix.pixelformat)
 			break;
 	}
 
-	if (format == NULL || format->fcc != fmt->fmt.pix.pixelformat) {
-		uvc_trace(UVC_TRACE_FORMAT, "Unsupported format 0x%08x.\n",
-				fmt->fmt.pix.pixelformat);
-		return -EINVAL;
+	if (i == stream->nformats) {
+		format = stream->def_format;
+		fmt->fmt.pix.pixelformat = format->fcc;
 	}
 
 	/* Find the closest image size. The distance between image sizes is

drivers/media/usb/uvc/uvc_video.c

@@ -1812,6 +1812,7 @@ int uvc_video_init(struct uvc_streaming *stream)
 	probe->bFormatIndex = format->index;
 	probe->bFrameIndex = frame->bFrameIndex;
 
+	stream->def_format = format;
 	stream->cur_format = format;
 	stream->cur_frame = frame;
 

drivers/media/usb/uvc/uvcvideo.h

@@ -436,6 +436,7 @@ struct uvc_streaming {
 	struct uvc_format *format;
 
 	struct uvc_streaming_control ctrl;
+	struct uvc_format *def_format;
 	struct uvc_format *cur_format;
 	struct uvc_frame *cur_frame;
 	/* Protect access to ctrl, cur_format, cur_frame and hardware video