media: v4l: Add V4L2-PIX-FMT-Y12P format

This is a packed grey-scale image format with a depth of 12 bits per
pixel. Two consecutive pixels are packed into 3 bytes. The first 2 bytes
contain the 8 high order bits of the pixels, and the 3rd byte contains
the 4 least significants bits of each pixel, in the same order.

Add the entry in userspace API, and document it.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst

@@ -114,6 +114,17 @@ are often referred to as greyscale formats.
       - ...
       - ...
 
+    * .. _V4L2-PIX-FMT-Y12P:
+
+      - ``V4L2_PIX_FMT_Y12P``
+      - 'Y12P'
+
+      - Y'\ :sub:`0`\ [11:4]
+      - Y'\ :sub:`1`\ [11:4]
+      - Y'\ :sub:`1`\ [3:0] Y'\ :sub:`0`\ [3:0]
+      - ...
+      - ...
+
     * .. _V4L2-PIX-FMT-Y14:
 
       - ``V4L2_PIX_FMT_Y14``

drivers/media/v4l2-core/v4l2-ioctl.c

@@ -1321,6 +1321,7 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
 	case V4L2_PIX_FMT_Y10BPACK:	descr = "10-bit Greyscale (Packed)"; break;
 	case V4L2_PIX_FMT_Y10P:		descr = "10-bit Greyscale (MIPI Packed)"; break;
 	case V4L2_PIX_FMT_IPU3_Y10:	descr = "10-bit greyscale (IPU3 Packed)"; break;
+	case V4L2_PIX_FMT_Y12P:		descr = "12-bit Greyscale (MIPI Packed)"; break;
 	case V4L2_PIX_FMT_Y8I:		descr = "Interleaved 8-bit Greyscale"; break;
 	case V4L2_PIX_FMT_Y12I:		descr = "Interleaved 12-bit Greyscale"; break;
 	case V4L2_PIX_FMT_Z16:		descr = "16-bit Depth"; break;

include/uapi/linux/videodev2.h

@@ -599,6 +599,7 @@ struct v4l2_pix_format {
 #define V4L2_PIX_FMT_Y10BPACK    v4l2_fourcc('Y', '1', '0', 'B') /* 10  Greyscale bit-packed */
 #define V4L2_PIX_FMT_Y10P    v4l2_fourcc('Y', '1', '0', 'P') /* 10  Greyscale, MIPI RAW10 packed */
 #define V4L2_PIX_FMT_IPU3_Y10		v4l2_fourcc('i', 'p', '3', 'y') /* IPU3 packed 10-bit greyscale */
+#define V4L2_PIX_FMT_Y12P    v4l2_fourcc('Y', '1', '2', 'P') /* 12  Greyscale, MIPI RAW12 packed */
 
 /* Palette formats */
 #define V4L2_PIX_FMT_PAL8    v4l2_fourcc('P', 'A', 'L', '8') /*  8  8-bit palette */