[Intel-gfx] Modeset API for KMS tests

[Damien Lespiau]

The goal of that series is to introduce a small mode setting API to write our
KMS tests, port kms_pipe_crc_basic and kms_cursor_crc to it and introduce a
new kms_plane test. To be more precise, the goals are:

  - Fewer lines per test,
  - Be able to switch between a "legacy" backend and an "atomic" one to help
    landing the latter (still has to be written).
  - Have a convenience place to put common KMS facilities and testing
 
Here an example of the look and feel of the API:

igt_display_t display;
igt_output_t output;

igt_display_init(&display);

for_each_connected_output(&display, output) {
        drmModeModeInfo *mode;
	struct kmstest_fb green_fb;
        igt_plane_t *primary;

	/*
	 * Create a green fb and display it on the primary plane
	 */
	mode = igt_output_get_mode(output);
        kmstest_create_color_fb(drm_fd,
				mode->hdisplay, mode->vdisplay,
                                DRM_FORMAT_XRGB8888,
                                false, /* tiled */
                                0.0, 1.0, 0.0,
                                &green_fb);

	igt_output_set_pipe(output, PIPE_B);
        primary = igt_ouput_get_plane(output, 0);
        igt_plane_set_fb(primary, &green_fb);
}

/* commit the display configuration */
igt_display_commit(&display);

igt_display_fini(&display);

A few interesting things about that API:

  - It exposes primary and cursor planes as igt_plane_t
  - It's possible to grab a debug output by defining IGT_DISPLAY_VERBOSE.
    This gives something like:

display: A.0: plane_set_fb(32)
display: A.2: plane_set_fb(33)
display: A.2: plane_set_position(132,132)
display: commit {
display:     LVDS-1: Selecting pipe A
display:     LVDS-1: SetCrtc pipe A, fb 32, panning (0, 0), mode 1366x768
display:     LVDS-1: SetCursor pipe A, fb 2 64x64
display:     LVDS-1: MoveCursor pipe A, (132, 132)
display: }

  - It's possible to stop at every commit() to inspect what is displayed,
    waiting for keypress with IGT_DISPLAY_WAIT_AT_COMMIT=1

For instance, one can run:

$ sudo IGT_DISPLAY_VERBOSE=1 IGT_DISPLAY_WAIT_AT_COMMIT=1 ./tests/kms_plane --run-subtest plane-position-hole-pipe-A-plane-2

HTH,

-- 
Damien