From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CF98B337BBA; Thu, 20 Nov 2025 14:09:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763647760; cv=none; b=GZz4ePDDkTAU3TBhMRYNzgWNoaOAOuOYEazVyiQjHAs8J/iQm1KgTs5Tol2MC8QSgZHrgqjLelgArk3mnrroUWUI9ZCdDe80dYS/Gfqhvm+Pl8Yrd6AHW3CHzQEMU9Mj7S0RO0M82GN5nXnFDuGbq86+N7q+1DeIPq4UVWTV0hI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763647760; c=relaxed/simple; bh=cB1MfBeclsVR7tg+ihgdmU0VGtZGLmlkem4dlSdvRNE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=YpizRAW6qOiCLodI2kRnanZMijxvvvqCTP++n7DxLKZLx7DpBhON4nL00SyIMiQQrTzbXrheTMzCHzb2ktot1sXonZ+YK3z78DgQ7jMtCfV7q29FlwKnsth8wiiNEQ6iE5MyFSVnSkH3lyKxUmuNOxIdghbVSllEkkiY5zA82u4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CVqEZpA4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CVqEZpA4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4EC6AC4CEF1; Thu, 20 Nov 2025 14:09:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763647760; bh=cB1MfBeclsVR7tg+ihgdmU0VGtZGLmlkem4dlSdvRNE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=CVqEZpA4Nhxw17SJ6Vlb53h4OvwmjmgrppItW3kIZG6sdTTYWjpPlGn4rQMDAeDc9 jWEkGWCbUwTt9Dt2afL8cx3GVtBatWPkjpKeglKw7d/lusU97BuPDWcZwDFb9y9OBT zeINZpzcVhQcmHtH28yKnbPEV/AAGjkPkL2XFsWKOMEHoYDxRIS1nIQo3YEroSaNdl S5LhNRuQJ/R62Xfq2HhkqGkfV0/EQJxdUiGhwXnJdLJuvysjbVRfxG/lQLs49pIRSf FHTj1JZ7n33i3YoRq+WnPd2bpS7LcJpQsdt82RA+av+cML3mNqSIbdGVQzP/V3RHiA 7w8E7a7gXKMNg== Message-ID: <3f66d2dd-4378-4d33-a0ce-3128c13ad6a5@kernel.org> Date: Thu, 20 Nov 2025 15:09:16 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] backlight: Add Congatec Board Controller (CGBC) backlight support To: petri.karhula@novatron.fi, Thomas Richard , Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org References: <20251118-cgbc-backlight-v1-1-cc6ac5301034@novatron.fi> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 18/11/2025 17:43, Petri Karhula via B4 Relay wrote: > + > +/** > + * Get current backlight brightness > + * @bl: Backlight device > + * > + * Returns the current brightness level by reading from hardware. > + * > + * Return: Current brightness level (0-100), or negative error code > + */ Why are you documenting standard API? > +static int cgbc_bl_get_brightness(struct backlight_device *bl) > +{ > + struct cgbc_bl_data *bl_data = bl_get_data(bl); > + int ret; > + > + /* Read current PWM brightness settings */ > + ret = cgbc_bl_read_pwm_settings(bl_data); > + > + if (ret < 0) { > + dev_err(bl_data->dev, "Failed to read PWM settings: %d\n", ret); > + return ret; > + } > + > + return bl_data->current_brightness; > +} > + > +/* Backlight device operations */ Huh? Can it be a GPIO device operations? > +static const struct backlight_ops cgbc_bl_ops = { > + .options = BL_CORE_SUSPENDRESUME, > + .update_status = cgbc_bl_update_status, > + .get_brightness = cgbc_bl_get_brightness, > +}; > + > +/** > + * Probe function for CGBC backlight driver > + * @pdev: Platform device > + * > + * Initializes the CGBC backlight driver and registers it with the > + * Linux backlight subsystem. > + * > + * Return: 0 on success, negative error code on failure Very redundant and useless comment. > + */ > +static int cgbc_bl_probe(struct platform_device *pdev) > +{ > + struct cgbc_device_data *cgbc = dev_get_drvdata(pdev->dev.parent); > + struct cgbc_bl_data *bl_data; > + struct backlight_properties props; > + struct backlight_device *bl_dev; > + int ret; > + > + bl_data = devm_kzalloc(&pdev->dev, sizeof(*bl_data), GFP_KERNEL); > + Drop blank line. There is never such line between allocation and check. > + if (!bl_data) > + return -ENOMEM; > + > + bl_data->dev = &pdev->dev; > + bl_data->cgbc = cgbc; > + > + ret = cgbc_bl_read_pwm_settings(bl_data); > + > + if (ret) { > + dev_err(&pdev->dev, "Failed to read initial PWM settings: %d\n", > + ret); return dev_err_probe > + return ret; > + } > + > + memset(&props, 0, sizeof(props)); > + props.type = BACKLIGHT_PLATFORM; > + props.max_brightness = CGBC_BL_MAX_BRIGHTNESS; > + props.brightness = bl_data->current_brightness; > + > + bl_dev = devm_backlight_device_register(&pdev->dev, "cgbc-backlight", > + &pdev->dev, bl_data, > + &cgbc_bl_ops, &props); > + > + if (IS_ERR(bl_dev)) { > + dev_err(&pdev->dev, "Failed to register backlight device\n"); return dev_err_probe > + return PTR_ERR(bl_dev); > + } > + > + bl_data->bl_dev = bl_dev; > + platform_set_drvdata(pdev, bl_data); > + > + dev_info(&pdev->dev, > + "CGBC backlight driver registered (brightness=%u)\n", > + bl_data->current_brightness); Drop. This does not look like useful printk message. Drivers should be silent on success: https://elixir.bootlin.com/linux/v6.15-rc7/source/Documentation/process/coding-style.rst#L913 https://elixir.bootlin.com/linux/v6.15-rc7/source/Documentation/process/debugging/driver_development_debugging_guide.rst#L79 > + > + return 0; > +} > + > +/** > + * Remove function for CGBC backlight driver > + * @pdev: Platform device > + * > + * The Linux device-managed resource framework (devres) does the cleanup. > + * No explicit cleanup is needed here. Drop such comments, they are not useful. Please write only useful comments, not ones stating obvious. > + */ > +static void cgbc_bl_remove(struct platform_device *pdev) > +{ > + dev_info(&pdev->dev, "CGBC backlight driver removed\n"); Drop, there is no such code in Linux kernel. Drop it. > +} > + Best regards, Krzysztof