linux-kernel - [PATCH v4 1/3] drm/panel-edp: add fat warning against adding new panel compatibles

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Message-Id: <20240614-edp-panel-drop-v4-1-4e0a112eec46@linaro.org>
Date: Fri, 14 Jun 2024 03:02:20 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Douglas Anderson <dianders@...omium.org>, 
 Neil Armstrong <neil.armstrong@...aro.org>, 
 Jessica Zhang <quic_jesszhan@...cinc.com>, Sam Ravnborg <sam@...nborg.org>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 linux-arm-msm@...r.kernel.org, linux-rockchip@...ts.infradead.org, 
 Jeffrey Hugo <quic_jhugo@...cinc.com>, devicetree@...r.kernel.org
Subject: [PATCH v4 1/3] drm/panel-edp: add fat warning against adding new
 panel compatibles

Add a fat warning against adding new panel compatibles to the panel-edp
driver. All new users of the eDP panels are supposed to use the generic
"edp-panel" compatible device on the AUX bus. The remaining compatibles
are either used by the existing DT or were used previously and are
retained for backwards compatibility.

Suggested-by: Doug Anderson <dianders@...omium.org>
Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>
Reviewed-by: Douglas Anderson <dianders@...omium.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
 drivers/gpu/drm/panel/panel-edp.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
index 67ab6915d6e4..85edfd3d59f3 100644
--- a/drivers/gpu/drm/panel/panel-edp.c
+++ b/drivers/gpu/drm/panel/panel-edp.c
@@ -1762,7 +1762,24 @@ static const struct of_device_id platform_of_match[] = {
 	{
 		/* Must be first */
 		.compatible = "edp-panel",
-	}, {
+	},
+	/*
+	 * Do not add panels to the list below unless they cannot be handled by
+	 * the generic edp-panel compatible.
+	 *
+	 * The only two valid reasons are:
+	 * - Because of the panel issues (e.g. broken EDID or broken
+	 *   identification).
+	 * - Because the eDP drivers didn't wire up the AUX bus properly.
+	 *   NOTE that, though this is a marginally valid reason,
+	 *   some justification needs to be made for why the platform can't
+	 *   wire up the AUX bus properly.
+	 *
+	 * In all other cases the platform should use the aux-bus and declare
+	 * the panel using the 'edp-panel' compatible as a device on the AUX
+	 * bus.
+	 */
+	{
 		.compatible = "auo,b101ean01",
 		.data = &auo_b101ean01,
 	}, {

-- 
2.39.2