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Message-Id: <20240917-hotplug-drm-bridge-v4-6-bc4dfee61be6@bootlin.com>
Date: Tue, 17 Sep 2024 10:53:10 +0200
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, 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>,
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>,
Derek Kiernan <derek.kiernan@....com>,
Dragan Cvetic <dragan.cvetic@....com>, Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Saravana Kannan <saravanak@...gle.com>,
Wolfram Sang <wsa+renesas@...g-engineering.com>,
"Rafael J. Wysocki" <rafael@...nel.org>, Lee Jones <lee@...nel.org>,
Daniel Thompson <daniel.thompson@...aro.org>,
Jingoo Han <jingoohan1@...il.com>, Helge Deller <deller@....de>
Cc: Paul Kocialkowski <contact@...lk.fr>,
Hervé Codina <herve.codina@...tlin.com>,
Thomas Petazzoni <thomas.petazzoni@...tlin.com>, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linux-i2c@...r.kernel.org, linux-fbdev@...r.kernel.org,
Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
Luca Ceresoli <luca.ceresoli@...tlin.com>
Subject: [PATCH v4 6/8] backlight: led-backlight: add devlink to supplier
LEDs
led-backlight is a consumer of one or multiple LED class devices, but no
devlink is created for such supplier-producer relationship. One consequence
is that removal ordered is not correctly enforced.
Issues happen for example with the following sections in a device tree
overlay:
// An LED driver chip
pca9632@62 {
compatible = "nxp,pca9632";
reg = <0x62>;
// ...
addon_led_pwm: led-pwm@3 {
reg = <3>;
label = "addon:led:pwm";
};
};
backlight-addon {
compatible = "led-backlight";
leds = <&addon_led_pwm>;
brightness-levels = <255>;
default-brightness-level = <255>;
};
On removal of the above overlay, the LED driver can be removed before the
backlight device, resulting in:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010
...
Call trace:
led_put+0xe0/0x140
devm_led_release+0x6c/0x98
Fix by adding a devlink between the consuming led-backlight device and the
supplying LED device.
Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
---
This patch first appeared in v4.
---
drivers/video/backlight/led_bl.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c
index c7aefcd6e4e3..bfbd80728036 100644
--- a/drivers/video/backlight/led_bl.c
+++ b/drivers/video/backlight/led_bl.c
@@ -209,6 +209,19 @@ static int led_bl_probe(struct platform_device *pdev)
return PTR_ERR(priv->bl_dev);
}
+ for (i = 0; i < priv->nb_leds; i++) {
+ struct device_link *link;
+
+ link = device_link_add(&pdev->dev, priv->leds[0]->dev->parent,
+ DL_FLAG_AUTOREMOVE_CONSUMER);
+ if (!link) {
+ dev_err(&pdev->dev, "Failed to add devlink (consumer %s, supplier %s)\n",
+ dev_name(&pdev->dev), dev_name(priv->leds[0]->dev->parent));
+ backlight_device_unregister(priv->bl_dev);
+ return -EINVAL;
+ }
+ }
+
for (i = 0; i < priv->nb_leds; i++) {
mutex_lock(&priv->leds[i]->led_access);
led_sysfs_disable(priv->leds[i]);
--
2.34.1
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