[rfc/wip] use v4l2 format info instead

[vicamo]

This is an attempt to remove struct v4l2l_format and use in kernel struct v4l2_format_info.

While moving toward videobuf2 framework, I'd like to reuse more and more already in kernel APIs as possible. This PR is going to change:

• how formats array is created:
  formats array used to carry fourcc, bpp info, etc., but it may not be synced with in kernel definitions and it's missing support for multiplane as well. While using videobuf2, we'd like to make sure there is no unexpected mismatch, especially in calculating buffer size. The formats array is now the one originally defined in v4l2_format_info() moved to the global namespace with additional entries added.

• format descriptions:
  kernel can help filling format description/flags since v4.2. Use the in kernel helper so that we can have identical names as other V4L2 based drivers do.

• supported formats set:

  • original: https://gist.github.com/vicamo/991eb7bfb96bab32d8ee989b648eb47d#file-supported-formats-orig
  • then: https://gist.github.com/vicamo/991eb7bfb96bab32d8ee989b648eb47d#file-supported-formats-new
  • diff: https://gist.github.com/vicamo/991eb7bfb96bab32d8ee989b648eb47d#file-supported-formats-diff (no removal from original set)

  note that following formats from the original set have no corresponding v4l2_format_info entry:

  V4L2_PIX_FMT_DV
  V4L2_PIX_FMT_H263
  V4L2_PIX_FMT_H264
  V4L2_PIX_FMT_H264_MVC
  V4L2_PIX_FMT_H264_NO_SC
  V4L2_PIX_FMT_HEVC
  V4L2_PIX_FMT_JPEG
  V4L2_PIX_FMT_MJPEG
  V4L2_PIX_FMT_MPEG
  V4L2_PIX_FMT_MPEG1
  V4L2_PIX_FMT_MPEG2
  V4L2_PIX_FMT_MPEG4
  V4L2_PIX_FMT_RGB332
  V4L2_PIX_FMT_RGB555X
  V4L2_PIX_FMT_RGB565X
  V4L2_PIX_FMT_VC1_ANNEX_G
  V4L2_PIX_FMT_VC1_ANNEX_L
  V4L2_PIX_FMT_VP8
  V4L2_PIX_FMT_VP9
  V4L2_PIX_FMT_XVID
  V4L2_PIX_FMT_Y10
  V4L2_PIX_FMT_Y12
  V4L2_PIX_FMT_Y16
  V4L2_PIX_FMT_Y4
  V4L2_PIX_FMT_Y41P
  V4L2_PIX_FMT_Y6
  V4L2_PIX_FMT_YUV32
  V4L2_PIX_FMT_YUV444
  V4L2_PIX_FMT_YUV555
  V4L2_PIX_FMT_YUV565
  V4L2_PIX_FMT_YYUV
  

Note this PR is not yet complete due the the lack of many format info entries in the implementation of v4l2_format_info even in current v5.12 kernel source. To be done some time later.

[vicamo]

=== Testing 4.4.0-148-generic ===
Building v4l2-loopback driver...
make -C /lib/modules/4.4.0-148-generic/build M=/__w/v4l2loopback/v4l2loopback modules
make[1]: Entering directory `/usr/src/linux-headers-4.4.0-148-generic'
  CC [M]  /__w/v4l2loopback/v4l2loopback/v4l2loopback.o
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /__w/v4l2loopback/v4l2loopback/v4l2loopback.mod.o
  LD [M]  /__w/v4l2loopback/v4l2loopback/v4l2loopback.ko
make[1]: Leaving directory `/usr/src/linux-headers-4.4.0-148-generic'
make -C utils
make[1]: Entering directory `/__w/v4l2loopback/v4l2loopback/utils'
cc  -I..   v4l2loopback-ctl.c   -o v4l2loopback-ctl
In file included from v4l2loopback-ctl.c:25:0:
../v4l2loopback_formats.h:131:2: error: initializer element is not constant
  V4L2_PIX_FMT_ARGB555X,
  ^
../v4l2loopback_formats.h:131:2: error: (near initialization for 'formats[23]')
../v4l2loopback_formats.h:135:2: error: initializer element is not constant
  V4L2_PIX_FMT_XRGB555X,
  ^
../v4l2loopback_formats.h:135:2: error: (near initialization for 'formats[24]')
../v4l2loopback_formats.h:223:2: error: initializer element is not constant
  V4L2_PIX_FMT_Y16_BE,
  ^
../v4l2loopback_formats.h:223:2: error: (near initialization for 'formats[46]')
../v4l2loopback_formats.h: In function 'backport_v4l_fill_fmtdesc':
../v4l2loopback_formats.h:1108:2: error: case label does not reduce to an integer constant
  case V4L2_PIX_FMT_ARGB555X: descr = "16-bit ARGB 1-5-5-5 BE"; break;
  ^
../v4l2loopback_formats.h:1109:2: error: case label does not reduce to an integer constant
  case V4L2_PIX_FMT_XRGB555X: descr = "16-bit XRGB 1-5-5-5 BE"; break;
  ^
../v4l2loopback_formats.h:1131:2: error: case label does not reduce to an integer constant
  case V4L2_PIX_FMT_Y16_BE: descr = "16-bit Greyscale BE"; break;
  ^
v4l2loopback-ctl.c: In function 'print_conf':
v4l2loopback-ctl.c:436:3: warning: format '%s' expects argument of type 'char *', but argument 2 has type 'struct v4l2_loopback_config *' [-Wformat=]
   printf("configuration: %s\n", cfg);
   ^
v4l2loopback-ctl.c: In function 'parse_caps':
v4l2loopback-ctl.c:656:6: warning: format '%c' expects argument of type 'char *', but argument 3 has type 'char (*)[5]' [-Wformat=]
      &caps->height, &caps->fps_num, &caps->fps_denom) <= 0) {
      ^
make[1]: *** [v4l2loopback-ctl] Error 1
make[1]: Leaving directory `/__w/v4l2loopback/v4l2loopback/utils'
make: *** [utils/v4l2loopback-ctl] Error 2

Interesting.

[umlaeute]

is this marked as draft because of the missing formats, or because it failed to build in the CI?

[vicamo]

is this marked as draft because of the missing formats, or because it failed to build in the CI?

Missing format info.

[vicamo]

@umlaeute it seems I overwritten your commit :)

Still a draft. Need to address those missing format info entries.

[vicamo]

Still a draft. Need to address those missing format info entries.

There are 147 formats not currently supported by v4l2_format_info(). That's probably too many to finish them in a short time. Taking V4L2_PIX_FMT_MPEG for example, it may even take a completely different way to calculate framesize than that provided by v4l2_fill_pixfmt().

We can shrink supported formats array to contain only supported ones.

[vicamo]

update: sort probed file paths to ensure a stable list is generated.

[vicamo]

Update:

• expose formats array originally embedded in v4l2_format_info(), so that we have a sync-ed formats array shared globally.
• always override v4l2_format_info() and v4l2_fill_pixfmt() for we're to reference the global supported formats array
• use #ifndef ... instead of #if !defined(...) in defining V4L2_FOO_FMT_BAR.
• add a few more format info entries to formats array