Hi Xavier, On Tue, Apr 26, 2022 at 11:34:55PM +0200, Xavier Roumegue (OSS) wrote: > 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. Agreed. As mentioned in a reply to another patch, I think it would be useful to explain this a bit more clearly. Hans mentioned in the review of the driver itself that there was a bug as an image width of 16 bits results in a grid width of 2. I think that's correct (a width between 1 and 16 pixels results in a single grid cell horizontally, and thus two vertices, on the left and right side of the cell), but it would benefit from an explanation. A small ascii art diagram could help. > >> + 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, Laurent Pinchart
