linux-kernel - [RFC PATCH 3/6] drm/dp: Add is_hpd_asserted() callback to struct drm_dp

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Message-Id: <20220408193536.RFC.3.Icf57bb12233a47727013c6ab69eebf803e22ebc1@changeid>
Date:   Fri,  8 Apr 2022 19:36:25 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     dri-devel@...ts.freedesktop.org
Cc:     Robert Foss <robert.foss@...aro.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        Philip Chen <philipchen@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Lyude Paul <lyude@...hat.com>,
        Maxime Ripard <maxime@...no.tech>, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 3/6] drm/dp: Add is_hpd_asserted() callback to struct drm_dp_aux

Sometimes it's useful for users of the DP AUX bus (like panels) to be
able to poll HPD. Let's add a callback that allows DP AUX busses
drivers to provide this.

Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

 include/drm/dp/drm_dp_helper.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/drm/dp/drm_dp_helper.h b/include/drm/dp/drm_dp_helper.h
index dad1442c91df..a12951319573 100644
--- a/include/drm/dp/drm_dp_helper.h
+++ b/include/drm/dp/drm_dp_helper.h
@@ -2021,6 +2021,20 @@ struct drm_dp_aux {
 	ssize_t (*transfer)(struct drm_dp_aux *aux,
 			    struct drm_dp_aux_msg *msg);
 
+	/**
+	 * @is_hpd_asserted: returns true if HPD is asserted
+	 *
+	 * This is mainly useful for eDP panels drivers to query whether
+	 * an eDP panel has finished powering on. This is an optional function.
+	 *
+	 * NOTE: this function specifically reports the state of the HPD pin
+	 * that's associated with the DP AUX channel. This is different from
+	 * the HPD concept in much of the rest of DRM which is more about
+	 * physical presence of a display. For eDP, for instance, a display is
+	 * assumed always present even if the HPD pin is deasserted.
+	 */
+	bool (*is_hpd_asserted)(struct drm_dp_aux *aux);
+
 	/**
 	 * @i2c_nack_count: Counts I2C NACKs, used for DP validation.
 	 */
-- 
2.35.1.1178.g4f1659d476-goog