Hi Sakari,

On Thu, Jul 05, 2018 at 03:48:02PM +0800, Yong wrote:

quoted

quoted

+
+/* -----------------------------------------------------------------------------
+ * Media Operations
+ */
+static int sun6i_video_formats_init(struct sun6i_video *video,
+				    const struct media_pad *remote)
+{
+	struct v4l2_subdev_mbus_code_enum mbus_code = { 0 };
+	struct sun6i_csi *csi = video->csi;
+	struct v4l2_format format;
+	struct v4l2_subdev *subdev;
+	u32 pad;
+	const u32 *pixformats;
+	int pixformat_count = 0;
+	u32 subdev_codes[32]; /* subdev format codes, 32 should be enough */
+	int codes_count = 0;
+	int num_fmts = 0;
+	int i, j;
+
+	pad = remote->index;
+	subdev = media_entity_to_v4l2_subdev(remote->entity);
+	if (subdev == NULL)
+		return -ENXIO;
+
+	/* Get supported pixformats of CSI */
+	pixformat_count = sun6i_csi_get_supported_pixformats(csi, &pixformats);
+	if (pixformat_count <= 0)
+		return -ENXIO;
+
+	/* Get subdev formats codes */
+	mbus_code.pad = pad;
+	mbus_code.which = V4L2_SUBDEV_FORMAT_ACTIVE;
+	while (!v4l2_subdev_call(subdev, pad, enum_mbus_code, NULL,
+				 &mbus_code)) {

The formats supported by the external sub-device may depend on horizontal
and vertical flipping. You shouldn't assume any particular configuration
here: instead, bridge drivers generally just need to make sure the formats
match in link validation when streaming is started. At least the CSI-2
receiver driver and the DMA engine driver (video device) should check the
configuration is valid. See e.g. the IPU3 driver:
drivers/media/pci/intel/ipu3/ipu3-cio2.c .

Can mbus_code be added dynamically ?
The code here only enum the mbus code and get the possible supported
pairs of pixformat and mbus by SoC. Not try to check if the formats
(width height ...) is valid or not. The formats validation will be 
in link validation when streaming is started as per your advise. 

Can you reply to this so that Yong has a chance to resubmit his serie
before the 4.19 merge window starts?

Or alternatively, is this something we can fix later on, once it's
merged?

Thanks!
Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com