[media] v4l: Support extending the v4l2_pix_format structure

The v4l2_pix_format structure has no reserved field. It is embedded in
the v4l2_framebuffer structure which has no reserved fields either, and
in the v4l2_format structure which has reserved fields that were not
previously required to be zeroed out by applications.

To allow extending v4l2_pix_format, inline it in the v4l2_framebuffer
structure, and use the priv field as a magic value to indicate that the
application has set all v4l2_pix_format extended fields and zeroed all
reserved fields following the v4l2_pix_format field in the v4l2_format
structure.

The availability of this API extension is reported to userspace through
the new V4L2_CAP_EXT_PIX_FORMAT capability flag. Just checking that the
priv field is still set to the magic value at [GS]_FMT return wouldn't
be enough, as older kernels don't zero the priv field on return.

To simplify the internal API towards drivers zero the extended fields
and set the priv field to the magic value for applications not aware of
the extensions.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index a498d8b58679..eb3bdd33816b 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -268,6 +268,7 @@ struct v4l2_capability {
 #define V4L2_CAP_MODULATOR		0x00080000  /* has a modulator */
 
 #define V4L2_CAP_SDR_CAPTURE		0x00100000  /* Is a SDR capture device */
+#define V4L2_CAP_EXT_PIX_FORMAT		0x00200000  /* Supports the extended pixel format */
 
 #define V4L2_CAP_READWRITE              0x01000000  /* read/write systemcalls */
 #define V4L2_CAP_ASYNCIO                0x02000000  /* async I/O */
@@ -448,6 +449,9 @@ struct v4l2_pix_format {
 #define V4L2_SDR_FMT_CU8          v4l2_fourcc('C', 'U', '0', '8') /* IQ u8 */
 #define V4L2_SDR_FMT_CU16LE       v4l2_fourcc('C', 'U', '1', '6') /* IQ u16le */
 
+/* priv field value to indicates that subsequent fields are valid. */
+#define V4L2_PIX_FMT_PRIV_MAGIC		0xfeedcafe
+
 /*
  *	F O R M A T   E N U M E R A T I O N
  */
@@ -752,7 +756,16 @@ struct v4l2_framebuffer {
 /* FIXME: in theory we should pass something like PCI device + memory
  * region + offset instead of some physical address */
 	void                    *base;
-	struct v4l2_pix_format	fmt;
+	struct {
+		__u32		width;
+		__u32		height;
+		__u32		pixelformat;
+		__u32		field;		/* enum v4l2_field */
+		__u32		bytesperline;	/* for padding, zero if unused */
+		__u32		sizeimage;
+		__u32		colorspace;	/* enum v4l2_colorspace */
+		__u32		priv;		/* reserved field, set to 0 */
+	} fmt;
 };
 /*  Flags for the 'capability' field. Read only */
 #define V4L2_FBUF_CAP_EXTERNOVERLAY	0x0001