[PATCH i-g-t v1 1/2] lib/igt_kms: Add helper to measure vblank sequence difference

[Naladala Ramanaidu]

Add a new helper to calculate the number of vblank intervals
between two consecutive events. This enhancement enables more
precise timing and synchronization measurements in simulation
environments.

Signed-off-by: Naladala Ramanaidu <ramanaidu.naladala at intel.com>
---
 lib/igt_kms.c | 21 +++++++++++++++++++++
 lib/igt_kms.h |  1 +
 2 files changed, 22 insertions(+)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index 7191bf92e..1dfe70637 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -2355,6 +2355,27 @@ static inline uint32_t pipe_select(int pipe)
 		return 0;
 }
 
+/**
+ * get_vblank_seq_diff:
+ * @fd: Opened drm file descriptor
+ * @pipe: Display pipe
+ *
+ * Measures the difference in vblank sequence numbers between
+ * two consecutive vblank events.
+ *
+ * Returns the number of vblank sequence numbers are elapsed.
+ */
+unsigned int get_vblank_seq_diff(int fd, enum pipe pipe)
+{
+	uint32_t vblank_start, vblank_end;
+
+	vblank_start = kmstest_get_vblank(fd, pipe, 0);
+	igt_wait_for_vblank(fd, pipe);
+	vblank_end = kmstest_get_vblank(fd, pipe, 0);
+
+	return vblank_end - vblank_start;
+}
+
 /**
  * kmstest_get_vblank:
  * @fd: Opened drm file descriptor
diff --git a/lib/igt_kms.h b/lib/igt_kms.h
index f140ad91a..01d1b8061 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -314,6 +314,7 @@ void kmstest_dumb_destroy(int fd, uint32_t handle);
 void kmstest_wait_for_pageflip(int fd);
 void kmstest_wait_for_pageflip_timeout(int fd, uint64_t timeout_us);
 unsigned int kmstest_get_vblank(int fd, int pipe, unsigned int flags);
+unsigned int get_vblank_seq_diff(int fd, enum pipe pipe);
 
 bool kms_has_vblank(int fd);
 
-- 
2.43.0