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 C39A315E5C2; Fri, 18 Jul 2025 17:36:51 +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=1752860211; cv=none; b=VjoNzuBPywtmxVu7xbG9SFTDvkoy+TjGYxJKv3sGC8tjAzgbAUNjX2qbCe2VmcFZlJN+MeVuYCl4sLj7LO1Rfx4ffyZV68PbLElL2Z/TN1306GqAxKYENwxQ/rgJ1C9Qm+S2hI/1078CK18OZ5G+nYXMJUmizSFp2/M2WP4+vZU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752860211; c=relaxed/simple; bh=3G0DSuma9EoRh+0cSstUnb2PnhnazXDdqCX1tROd9/U=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=iraxiyvqFVihwFW27b2hPZYtFrSOa1BL2/SzhZ00+lK3+YZWbYdW3ZN2abbOALjWj4BvDxbPrWgA4NrbEQzS6lAhQiI4iRjNJT8V7gIqaX2inQv/Dvk20O87FwLN1S7rhvKi0IuSnUUVhwJJsOCTqPsFdf4/Q0ox9x3BzTnkyCI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Du+zVQmT; 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="Du+zVQmT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AC6A1C4CEEB; Fri, 18 Jul 2025 17:36:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752860211; bh=3G0DSuma9EoRh+0cSstUnb2PnhnazXDdqCX1tROd9/U=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=Du+zVQmTS6WbjJUtbJ4BCs7wJ7Vipjf6ogBECh36POXjccz9iROAlMR7PehrAUOiP eVkeyvrSjIhjjbd+vd1bsEgxzVIKFbXJhaPm7jyVOe7gnFzcZlyz0wC9mGHiNkRcgM pW9QfY3xN91fwSPtH8yqODM5gx3tbtx7fgwS4ffpfn8AwH0/+zmtm5FD7ZmkO3UOOw PTdLfHWigxSTSEvaIjtNSLB56K+cdYqaCKn1ifaTBkUR3uAwbanh2N2gKthfdinxDS +UJV7jMcdbpnhcgYdYJI4RaKTCffE6arC9BxWTu+zbHNkROo2TvEeEEzpb1CvlerOI Ju8fURhBaz5wA== Date: Fri, 18 Jul 2025 12:36:48 -0500 From: Bjorn Helgaas To: Mario Limonciello Cc: David Airlie , Bjorn Helgaas , Alex Deucher , Christian =?utf-8?B?S8O2bmln?= , 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 Subject: Re: [PATCH v9 9/9] PCI: Add a new 'boot_display' attribute Message-ID: <20250718173648.GA2704349@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jul 18, 2025 at 12:29:05PM -0500, Mario Limonciello wrote: > 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 What's missing? The specifics might be helpful if someone has another crack at getting rid of pci_create_sysfs_dev_files() in the future. > 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 > > > >