Subject: [PATCH v5 2/4] drm/dp: Add helper to validate DP lane counts

From: Damon Ding <[email-masked]>
Date: Thu, 4 Jun 2026 16:52:18 +0800

Add a generic helper function drm_dp_lane_count_is_valid() to check
if a DisplayPort lane count is valid. According to the DP specification,
only 1, 2, or 4 lanes are supported.

This helper avoids duplicating DP lane count validation logic across
individual DisplayPort drivers.

Suggested-by: Luca Ceresoli <[email-masked]>
Signed-off-by: Damon Ding <[email-masked]>
---
 include/drm/display/drm_dp_helper.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
index 8c2d77a032f0..c904cb480d84 100644
--- a/include/drm/display/drm_dp_helper.h
+++ b/include/drm/display/drm_dp_helper.h
@@ -138,6 +138,12 @@ bool drm_dp_as_sdp_supported(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_C
 
 int drm_dp_psr_setup_time(const u8 psr_cap[EDP_PSR_RECEIVER_CAP_SIZE]);
 
+static inline bool
+drm_dp_lane_count_is_valid(int lane_count)
+{
+	return lane_count == 1 || lane_count == 2 || lane_count == 4;
+}
+
 static inline int
 drm_dp_max_link_rate(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
 {
-- 
2.34.1