media: Add a Kconfig option for the Request API

The Request API is now merged to the kernel but the confidence on the
stability of that API is not great, especially regarding the interaction
with V4L2.

Add a Kconfig option for the API, with a scary-looking warning.

The patch itself disables request creation as well as does not advertise
them as buffer flags. The driver requiring requests (cedrus) now depends
on the Kconfig option as well.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/Kconfig

@@ -110,6 +110,19 @@ config MEDIA_CONTROLLER_DVB
 
 	  This is currently experimental.
 
+config MEDIA_CONTROLLER_REQUEST_API
+	bool "Enable Media controller Request API (EXPERIMENTAL)"
+	depends on MEDIA_CONTROLLER && STAGING_MEDIA
+	default n
+	---help---
+	  DO NOT ENABLE THIS OPTION UNLESS YOU KNOW WHAT YOU'RE DOING.
+
+	  This option enables the Request API for the Media controller and V4L2
+	  interfaces. It is currently needed by a few stateless codec drivers.
+
+	  There is currently no intention to provide API or ABI stability for
+	  this new API as of yet.
+
 #
 # Video4Linux support
 #	Only enables if one of the V4L2 types (ATV, webcam, radio) is selected

drivers/media/common/videobuf2/videobuf2-v4l2.c

@@ -634,8 +634,10 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_USERPTR;
 	if (q->io_modes & VB2_DMABUF)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF;
+#ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API
 	if (q->supports_requests)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
+#endif
 }
 
 int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)

drivers/media/media-device.c

@@ -381,10 +381,14 @@ static long media_device_get_topology(struct media_device *mdev, void *arg)
 static long media_device_request_alloc(struct media_device *mdev,
 				       int *alloc_fd)
 {
+#ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API
 	if (!mdev->ops || !mdev->ops->req_validate || !mdev->ops->req_queue)
 		return -ENOTTY;
 
 	return media_request_alloc(mdev, alloc_fd);
+#else
+	return -ENOTTY;
+#endif
 }
 
 static long copy_arg_from_user(void *karg, void __user *uarg, unsigned int cmd)

drivers/staging/media/sunxi/cedrus/Kconfig

@@ -3,6 +3,7 @@ config VIDEO_SUNXI_CEDRUS
 	depends on VIDEO_DEV && VIDEO_V4L2 && MEDIA_CONTROLLER
 	depends on HAS_DMA
 	depends on OF
+	depends on MEDIA_CONTROLLER_REQUEST_API
 	select SUNXI_SRAM
 	select VIDEOBUF2_DMA_CONTIG
 	select V4L2_MEM2MEM_DEV