From patchwork Mon May 19 20:19:11 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luca Ceresoli X-Patchwork-Id: 891169 Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A6BCA20E715; Mon, 19 May 2025 20:19:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.198 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747685988; cv=none; b=U0iUFQ3U5lBRfme0V24WSWmV5cRQkvkz7n05V0oxloiiLAlCasgem4MREj9a4cV5gJsZd1vT+jve/eImsjSP9gp/B79WW/xqNB6Xf7O6KJAKU/Sk1khiMebhkwKcqaF5BGxZfngL21kgQWikjZB3XBwdBVNfcd3WWY12KcLcvGo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747685988; c=relaxed/simple; bh=CvgBHlBA2zl4zA1POiyt0S87W2ZxTO4B8wUiqIIjYZs=; 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d=bootlin.com; s=gm1; t=1747685983; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=d+ZhZFdcyO7MijMi13gLvQU8JeWL+SnKqaTCtITt0UM=; b=IHp2zGCbtinQAZCN/tsAolCu3i5Dn5vBz3mgLCp17U3Dn7K42JlEPgAwY9TaW8VhwUvLtL KMF/soMGNjN0C54a0MWN6wPkwTgQbj+7lsCFtRHPT28CjW+4QSLnejw7LSEBxfvc4NonQw jq3qTZxVgO1PRAGPMAd9kvvR5JQU2BHrm/NwDDYdGOxyTQl+GHqIfpwdDYpvmjb56tSLw5 S2jpK1ywSQ3GfCe2o5uyzUod2EwOc5utHiGj3F0w7OwDcXe8WHKOwlATrl028mAB7lbdtk 8f19TTZfiQHCoJOhLcRnNWWubpj25XDBQtEU3NqagVi61drfvhIBEUrRNqoxJw== From: Luca Ceresoli Date: Mon, 19 May 2025 22:19:11 +0200 Subject: [PATCH v6] backlight: led-backlight: add devlink to supplier LEDs Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250519-led-backlight-add-devlink-to-supplier-class-device-v6-1-845224aeb2ce@bootlin.com> X-B4-Tracking: v=1; b=H4sIAD6SK2gC/6WOTQ6CMBCFr0K6dgyStkZX3sOwKJ0BJlRK2tpoC He3cAWX33t5P6uIFJiiuFerCJQ5sp8L6FMl7GjmgYCxsGjqRtXqcgNHCJ2xk+NhTGAQASk7nid IHuJ7WRxTAOtMjLvDlkAjWUm1lFIZUYqXQD1/jtFnW3jkmHz4Hh+y2tW/5rKCC1w16h6loa7pH 533qWTO1r9Eu23bD2WrLvz2AAAA X-Change-ID: 20250519-led-backlight-add-devlink-to-supplier-class-device-6dec4e04445a To: Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller , Tony Lindgren , Pavel Machek , Jean-Jacques Hiblot , Tomi Valkeinen Cc: Saravana Kannan , =?utf-8?q?Herv=C3=A9_Codina?= , Thomas Petazzoni , Daniel Thompson , dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Alexander Sverdlin , Luca Ceresoli X-Mailer: b4 0.14.2 X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgdefvddvfedvucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuifetpfffkfdpucggtfgfnhhsuhgsshgtrhhisggvnecuuegrihhlohhuthemuceftddunecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpefhfffugggtgffkvfevofesthejredtredtjeenucfhrhhomhepnfhutggrucevvghrvghsohhlihcuoehluhgtrgdrtggvrhgvshholhhisegsohhothhlihhnrdgtohhmqeenucggtffrrghtthgvrhhnpedvueelteffuedthfevvdejffdutdetjedthfffvdehvdelveetkeejjefgjefgheenucffohhmrghinhepkhgvrhhnvghlrdhorhhgnecukfhppedvrgdtvdemieejtdemvddtvddtmegvrgdtudemsggvgedumeelhegvjeemfeegfeemledufegvnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehinhgvthepvdgrtddvmeeijedtmedvtddvtdemvggrtddumegsvgegudemleehvgejmeefgeefmeeludefvgdphhgvlhhopegludelvddrudeikedrudejkedrjeehngdpmhgrihhlfhhrohhmpehluhgtrgdrtggvrhgvshholhhisegsohhothhlihhnrdgtohhmpdhnsggprhgtphhtthhopedujedprhgtphhtthhopegurghnihgvlhdrthhhohhmphhsohhnsehlihhnrghrohdrohhrghdprhgtphhtthhopehlihhnuhigqdhfsgguvghvsehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtohepj hhinhhgohhohhgrnhdusehgmhgrihhlrdgtohhmpdhrtghpthhtoheplhgvvgeskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepthhhohhmrghsrdhpvghtrgiiiihonhhisegsohhothhlihhnrdgtohhmpdhrtghpthhtohepshgrrhgrvhgrnhgrkhesghhoohhglhgvrdgtohhmpdhrtghpthhtohephhgvrhhvvgdrtghoughinhgrsegsohhothhlihhnrdgtohhmpdhrtghpthhtoheprghlvgigrghnuggvrhdrshhvvghrughlihhnsehgmhgrihhlrdgtohhm X-GND-Sasl: luca.ceresoli@bootlin.com led-backlight is a consumer of one or multiple LED class devices, but devlink is currently unable to create correct supplier-producer links when the supplier is a class device. It creates instead a link where the supplier is the parent of the expected device. One consequence is that removal order 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>; }; In this example, the devlink should be created between the backlight-addon (consumer) and the pca9632@62 (supplier). Instead it is created between the backlight-addon (consumer) and the parent of the pca9632@62, which is typically the I2C bus adapter. 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 Another way to reproduce the bug without any device tree overlays is unbinding the LED class device (pca9632@62) before unbinding the consumer (backlight-addon): echo 11-0062 >/sys/bus/i2c/drivers/leds-pca963x/unbind echo ...backlight-dock >/sys/bus/platform/drivers/led-backlight/unbind Fix by adding a devlink between the consuming led-backlight device and the supplying LED device, as other drivers and subsystems do as well. Tested-by: Alexander Sverdlin Fixes: ae232e45acf9 ("backlight: add led-backlight driver") Signed-off-by: Luca Ceresoli Reviewed-by: Herve Codina --- Changes in v6: - EDITME: describe what is new in this series revision. - EDITME: use bulletpoints and terse descriptions. - Link to v5: https://lore.kernel.org/r/20250519-led-backlight-add-devlink-to-supplier-class-device-v5-1-76d6fd4aeb2f@bootlin.com --- Changes in v6: - fix incorrect array index - further improve commit message - Link to v5: https://lore.kernel.org/r/20250519-led-backlight-add-devlink-to-supplier-class-device-v5-1-76d6fd4aeb2f@bootlin.com Changes in v5: - separated this patch as a standalone patch - improved commit message, adding feedback from Alexander - no code changes This patch first appeared in the v4 of a longer series, even though the issue is orthogonal: https://lore.kernel.org/all/20240917-hotplug-drm-bridge-v4-6-bc4dfee61be6@bootlin.com/ --- drivers/video/backlight/led_bl.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) --- base-commit: a5806cd506af5a7c19bcd596e4708b5c464bfd21 change-id: 20250519-led-backlight-add-devlink-to-supplier-class-device-6dec4e04445a Best regards, diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c index d2db157b2c290adc3a159023e9e2394fc877388c..0ed585eb27903df43651c5365f479f7865cc8a95 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[i]->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[i]->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]);