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 0F3DC1C7017; Fri, 18 Jul 2025 17:29:08 +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=1752859749; cv=none; b=YeIdsBaEhiaOacNGUNhPPFOHpYoROS6P2OIvUMIEyhMN/ksKVR0U38SsvV48d+/7cAbmzE8IXKjOR8D3/boikMdOeuV3y/OBIB0ceQqZvS3zgQC74F8Z5bWtpADeVz3RVRfLVcFb/rbUGUqAapkV13d05flWo4qoW5zuZ7rK2Oc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752859749; c=relaxed/simple; bh=wf2avfRaqrJbyST3UyYxQ4ZifExp4p/EYoTF5IOX4og=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ltZ1BG8RG+/rHym1Pi7M288iiBY4FOV0sQ7GNjKLJdVTvvuBWB/eMvg0DlcBdx2GR17leRkhh48PT3/5lgsqiqrUSTEldjIIiPEvrNisXvBfPOX1hv3AtNg+mC6dTEL8ZRANc6qZ30j+BR3M+fqcy77MK0GUZft+kz9T5svVaGE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oyH3+WVK; 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="oyH3+WVK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 22618C4CEEB; Fri, 18 Jul 2025 17:29:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752859748; bh=wf2avfRaqrJbyST3UyYxQ4ZifExp4p/EYoTF5IOX4og=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=oyH3+WVK+94ytu5NuypH0ZbrxnNvx7RPO9oCOGa6WbgJuE1xZPcQ2STcJW2KoiAp/ qKhB/KbYJwrjekI6pYGFvptl61nwKOoMR/V8Yh0Vn3l3iTcw0krdE2jhfGQ0aTuWfw 9JCKRJeBR65tpSt55AdSDeWOfxbaMjBtnOYGFVFrFdZCFYL6netTPMTj5+uAc0hLS5 biDg7wo9Wbz3vNKA2CvzBSALJPdmAKZ7jwoJ5lTats7na+696mdexLBPWcfnfAu6L/ IyTptfws8krwmPdyOeMlDzXzvdVhXvdaIcm7LX5L6sVW2YhhF+ugNSkkmcDJSMJme0 MfINcWjsQaDeg== Message-ID: Date: Fri, 18 Jul 2025 12:29:05 -0500 Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 9/9] PCI: Add a new 'boot_display' attribute To: Bjorn Helgaas Cc: David Airlie , Bjorn Helgaas , Alex Deucher , =?UTF-8?Q?Christian_K=C3=B6nig?= , Simona Vetter , Lukas Wunner , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Woodhouse , Lu Baolu , Joerg Roedel , Will Deacon , Robin Murphy , Alex Williamson , Jaroslav Kysela , Takashi Iwai , "open list:DRM DRIVERS" , open list , "open list:INTEL IOMMU (VT-d)" , "open list:PCI SUBSYSTEM" , "open list:VFIO DRIVER" , "open list:SOUND" , Daniel Dadap , Mario Limonciello References: <20250718172545.GA2703510@bhelgaas> Content-Language: en-US From: Mario Limonciello In-Reply-To: <20250718172545.GA2703510@bhelgaas> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/18/2025 12:25 PM, Bjorn Helgaas wrote: > On Thu, Jul 17, 2025 at 12:38:12PM -0500, Mario Limonciello wrote: >> From: Mario Limonciello >> >> On systems with multiple GPUs there can be uncertainty which GPU is the >> primary one used to drive the display at bootup. In some desktop >> environments this can lead to increased power consumption because >> secondary GPUs may be used for rendering and never go to a low power >> state. In order to disambiguate this add a new sysfs attribute >> 'boot_display' that uses the output of video_is_primary_device() to >> populate whether a PCI device was used for driving the display. > >> +What: /sys/bus/pci/devices/.../boot_display >> +Date: October 2025 >> +Contact: Linux PCI developers >> +Description: >> + This file indicates that displays connected to the device were >> + used to display the boot sequence. If a display connected to >> + the device was used to display the boot sequence the file will >> + be present and contain "1". > >> int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev) >> { >> + int retval; >> + >> if (!sysfs_initialized) >> return -EACCES; >> >> + retval = pci_create_boot_display_file(pdev); > > In addition to Mani's question about whether /sys/bus/pci/ is the > right place for this (which is a very good question), it's also been > pointed out to me that we've been trying to get rid of > pci_create_sysfs_dev_files() for years. > > If it's possible to make this a static attribute that would be much, > much cleaner. Right - I tried to do this, but the problem is at the time the PCI device is created the information needed to make the judgement isn't ready. The options end up being: * a sysfs file for every display device with 0/1 * a sysfs file that is not accurate until later in the boot So IMO it /needs/ to come later. > >> + if (retval) >> + return retval; >> + >> return pci_create_resource_files(pdev); >> } >> >> @@ -1671,6 +1716,7 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev) >> if (!sysfs_initialized) >> return; >> >> + pci_remove_boot_display_file(pdev); >> pci_remove_resource_files(pdev); >> } >> >> -- >> 2.43.0 >>