linux-kernel - [PATCH 01/32] drm/mipi-dsi: add sanity check of lane number in mipi_dsi

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Message-Id: <20250625-drm-dsi-host-no-device-ptr-v1-1-e36bc258a7c5@bootlin.com>
Date: Wed, 25 Jun 2025 18:45:05 +0200
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Andrzej Hajda <andrzej.hajda@...el.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
 Inki Dae <inki.dae@...sung.com>, Jagan Teki <jagan@...rulasolutions.com>, 
 Marek Szyprowski <m.szyprowski@...sung.com>, 
 Jani Nikula <jani.nikula@...ux.intel.com>, 
 Dmitry Baryshkov <lumag@...nel.org>
Cc: Hui Pu <Hui.Pu@...ealthcare.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 linux-sunxi@...ts.linux.dev, Luca Ceresoli <luca.ceresoli@...tlin.com>
Subject: [PATCH 01/32] drm/mipi-dsi: add sanity check of lane number in
 mipi_dsi_attach()

Several drivers do some sanity checks on the lane number. Checking it is
non-zero will allow to remove such checks.

Additionally, we are about to move to an .attach_new host op which won't
pass a pointer that the host driver can store. This will prevent host
drivers to check for the presence of a device by storing such pointer and
checking whether it is NULL. As a replacement, host drivers will be able to
check the lane number to be non-zero, so ensuring a zero value is never
passed along will make such checks robust.

Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
---
 drivers/gpu/drm/drm_mipi_dsi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index a00d76443128e4972f939a8c9e26d949d2b30bb9..82d4f9c1de5fbc60f32d0b0baf41e1bd2991ebe4 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -379,6 +379,9 @@ int mipi_dsi_attach(struct mipi_dsi_device *dsi)
 	if (!ops || !ops->attach)
 		return -ENOSYS;
 
+	if (dsi->lanes < 1)
+		return dev_err_probe(&dsi->dev, -EINVAL, "Incorrect lanes number\n");
+
 	ret = ops->attach(dsi->host, dsi);
 	if (ret)
 		return ret;

-- 
2.49.0