[PATCH i-g-t 5/8] lib/kms: Simplify kmstest_get_vbl_flag()

Ville Syrjala
2026-01-13T12:05:02Z

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Simplify kmstest_get_vbl_flag() by observing that:
- '0 << DRM_VBLANK_HIGH_CRTC_SHIFT == 0' so we don't
have to have special treatment for crtc_offset==0
- the kernel will treat '1 << DRM_VBLANK_HIGH_CRTC_SHIFT'
and 'DRM_VBLANK_SECONDARY' identically, so the
crtc_offset==1 special case can also go away.

DRM_VBLANK_HIGH_CRTC_* was added in 2011, so there is no real
point in keeping support for old kernels that don't have it.
And in case someone is crazy enoguh to run igt on a kernel older
than that we can toss in a DRM_CAP_VBLANK_HIGH_CRTC check into
igt_display_require().

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
lib/igt_kms.c | 18 +++++++-----------
1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index 8581a218a83c..3cb1273f3041 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -3186,6 +3186,8 @@ void igt_display_require(igt_display_t *display, int drm_fd)
display->drm_fd = drm_fd;
is_intel_dev = is_intel_device(drm_fd);

+ igt_require(igt_has_drm_cap(drm_fd, DRM_CAP_VBLANK_HIGH_CRTC));
+
if (drmSetClientCap(drm_fd, DRM_CLIENT_CAP_ATOMIC, 1) == 0)
display->is_atomic = 1;

@@ -6125,19 +6127,13 @@ void igt_cleanup_uevents(struct udev_monitor *mon)
*/
uint32_t kmstest_get_vbl_flag(int crtc_offset)
{
- uint32_t pipe_id;
+ uint32_t flag;

- if (crtc_offset == 0)
- pipe_id = 0;
- else if (crtc_offset == 1)
- pipe_id = _DRM_VBLANK_SECONDARY;
- else {
- uint32_t pipe_flag = crtc_offset << 1;
- igt_assert(!(pipe_flag & ~DRM_VBLANK_HIGH_CRTC_MASK));
- pipe_id = pipe_flag;
- }
+ flag = crtc_offset << DRM_VBLANK_HIGH_CRTC_SHIFT;
+
+ igt_assert_eq(flag & ~DRM_VBLANK_HIGH_CRTC_MASK, 0);

- return pipe_id;
+ return flag;
}

static inline const uint32_t *
--
2.51.2