Hello Hans,
On 4/25/22 08:57, Hans Verkuil wrote:
On 28/03/2022 16:13, Xavier Roumegue wrote:
The DW100 driver gets the dewarping mapping as a binary blob from the
userspace application through a custom control.
The blob format is hardware specific so create a dedicated control for
this purpose.
Signed-off-by: Xavier Roumegue <xavier.roumegue@xxxxxxxxxxx>
---
Documentation/userspace-api/media/drivers/dw100.rst | 12 ++++++++++++
include/uapi/linux/dw100.h | 11 +++++++++++
2 files changed, 23 insertions(+)
create mode 100644 include/uapi/linux/dw100.h
diff --git a/Documentation/userspace-api/media/drivers/dw100.rst b/Documentation/userspace-api/media/drivers/dw100.rst
index 4cd55c75628e..f6d684cadf26 100644
--- a/Documentation/userspace-api/media/drivers/dw100.rst
+++ b/Documentation/userspace-api/media/drivers/dw100.rst
@@ -20,4 +20,16 @@ match the expected size inherited from the destination image resolution.
More details on the DW100 hardware operations can be found in
*chapter 13.15 DeWarp* of IMX8MP_ reference manuel.
+The Vivante DW100 m2m driver implements the following driver-specific control:
+
+``V4L2_CID_DW100_DEWARPING_16x16_VERTEX_MAP (integer)``
(integer) -> (__u32 array)
But should this be a __u32 array at all? Wouldn't a __u16 array make more sense?
This is indeed debatable. But the array is describing vertices positions
on a 2D dimension space, and thus its size is always even.
More importantly, the array must follow the format imposed by the
hardware which expects __u16 pairs packed in a __u32.
Lastly, the lut (map) register size unit is __u32.
Hence, IMHO, using __u32 might make more sense to highlight its hardware
dependency.
+ Specifies to DW100 driver its dewarping map (aka LUT) blob as described in
+ *chapter 13.15.2.3 Dewarping Remap* of IMX8MP_ reference manual as an U32
+ dynamic array. The image is divided into many small 16x16 blocks. If the
+ width of the image is not divisible by 16, the size of the rightmost block
+ is the remainder.
Isn't the same true for the height?
Yes, will update accordingly.
The dewarping map only saves the vertex coordinates of the
+ block. The dewarping grid map is comprised of vertex coordinates for x and y.
+ Each x, y coordinate register uses 16 bits (UQ12.4) to record the coordinate
As mentioned before, UQ12.4 is not necessarily a standard notation. 'unsigned 12.4
fixed point' is better, but you also need to specify exactly where the bits are
stored inside the __u16. I.e.: 'the integer part is stored in the 12 most significant
bits, and the fractional part is stored in the 4 least significant bits of the __u16.'
+ address, with the Y coordinate in the upper bits and X in the lower bits.
And with a __u16 array this becomes: 'The array contains pairs of X, Y coordinates.'
Or something along those lines.
+
.. _IMX8MP: https://www.nxp.com/webapp/Download?colCode=IMX8MPRM
diff --git a/include/uapi/linux/dw100.h b/include/uapi/linux/dw100.h
new file mode 100644
index 000000000000..7fdcf2bf42e5
--- /dev/null
+++ b/include/uapi/linux/dw100.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
+/* Copyright 2022 NXP */
+
+#ifndef __UAPI_DW100_H__
+#define __UAPI_DW100_H__
+
+#include <linux/v4l2-controls.h>
+
Add a comment referring to the Documentation/userspace-api/media/drivers/dw100.rst
documentation so users of this control know where to find the associated
documentation.
+#define V4L2_CID_DW100_DEWARPING_16x16_VERTEX_MAP (V4L2_CID_USER_DW100_BASE + 1)
+
+#endif
Regards,
Hans
Regards,
Xavier
