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

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Message-Id: <20240523-edp-panel-drop-v1-1-045d62511d09@linaro.org>
Date: Thu, 23 May 2024 01:07:00 +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>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH RFC] 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>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
The following compatibles were never used by the devices supported by
the upstream kernel and are a subject to possible removal:

- auo,b133han05
- auo,b140han06
- ivo,m133nwf4-r0
- lg,lp097qx1-spa1
- lg,lp129qe
- samsung,lsn122dl01-c01
- samsung,ltn140at29-301
- sharp,ld-d5116z01b
- sharp,lq140m1jw46
- starry,kr122ea0sra

I'm considering dropping them, unless there is a good reason not to do
so.
---
 drivers/gpu/drm/panel/panel-edp.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
index 6db277efcbb7..95b25ec67168 100644
--- a/drivers/gpu/drm/panel/panel-edp.c
+++ b/drivers/gpu/drm/panel/panel-edp.c
@@ -1776,7 +1776,23 @@ 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 platform which uses the panel didn'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. The lack of the aux-bus support is not a valid case. Platforms
+	 * are urged to be converted to declaring panels in a proper way.
+	 */
+	{
 		.compatible = "auo,b101ean01",
 		.data = &auo_b101ean01,
 	}, {

---
base-commit: 8314289a8d50a4e05d8ece1ae0445a3b57bb4d3b
change-id: 20240523-edp-panel-drop-00aa239b3c6b

Best regards,
-- 
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>