[PATCH i-g-t 1/3] lib/igt_kms: Drop all stale events on first commit.

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

I've been trying to make kms_cursor_legacy work when subtests fail.
Other subtests will start failing too because of expired events or
stale pipe crc. The latter can be resolved in the test, but the former
could affect other tests

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
---
 lib/igt_kms.c | 39 ++++++++++++++++++++++++++++++++++++++-
 lib/igt_kms.h |  1 +
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index 223dbe4ca565..9e14f071ea57 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -2943,7 +2943,10 @@ display_commit_changed(igt_display_t *display, enum igt_commit_style s)
 			output->changed &= 1 << IGT_CONNECTOR_CRTC_ID;
 	}
 
-	display->first_commit = false;
+	if (display->first_commit) {
+		igt_display_drop_events(display);
+		display->first_commit = false;
+	}
 }
 
 /*
@@ -3024,6 +3027,10 @@ int igt_display_try_commit_atomic(igt_display_t *display, uint32_t flags, void *
 	if (ret || (flags & DRM_MODE_ATOMIC_TEST_ONLY))
 		return ret;
 
+	if (display->first_commit)
+		igt_fail_on_f(flags & (DRM_MODE_PAGE_FLIP_EVENT | DRM_MODE_ATOMIC_NONBLOCK),
+			      "First commit has to drop all stale events\n");
+
 	display_commit_changed(display, COMMIT_ATOMIC);
 
 	igt_debug_wait_for_keypress("modeset");
@@ -3121,6 +3128,36 @@ int igt_display_commit(igt_display_t *display)
 	return igt_display_commit2(display, COMMIT_LEGACY);
 }
 
+/**
+ * igt_display_drop_events:
+ * @display: DRM device handle
+ *
+ * Nonblockingly reads all current events and drops them, for highest
+ * reliablility, call igt_display_commit2() first to flush all outstanding
+ * events.
+ *
+ * This will be called on the first commit after igt_display_reset() too,
+ * to make sure any stale events are flushed.
+ */
+void igt_display_drop_events(igt_display_t *display)
+{
+	/* Clear all events from drm fd. */
+	struct pollfd pfd = {
+		.fd = display->drm_fd,
+		.events = POLLIN
+	};
+
+	while (poll(&pfd, 1, 0) > 0) {
+		struct drm_event ev;
+		char buf[128];
+
+		read(display->drm_fd, &ev, sizeof(ev));
+		igt_info("Dropping event type %u length %u\n", ev.type, ev.length);
+		igt_assert(ev.length <= sizeof(buf));
+		read(display->drm_fd, buf, ev.length);
+	}
+}
+
 const char *igt_output_name(igt_output_t *output)
 {
 	return output->name;
diff --git a/lib/igt_kms.h b/lib/igt_kms.h
index 2a480bf39956..342881a69177 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -360,6 +360,7 @@ int  igt_display_commit(igt_display_t *display);
 int  igt_display_try_commit_atomic(igt_display_t *display, uint32_t flags, void *user_data);
 void igt_display_commit_atomic(igt_display_t *display, uint32_t flags, void *user_data);
 int  igt_display_try_commit2(igt_display_t *display, enum igt_commit_style s);
+void igt_display_drop_events(igt_display_t *display);
 int  igt_display_get_n_pipes(igt_display_t *display);
 void igt_display_require_output(igt_display_t *display);
 void igt_display_require_output_on_pipe(igt_display_t *display, enum pipe pipe);
-- 
2.15.1

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