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Message-ID: <704d2a80-79bb-4247-a2aa-25bd3eb9a7e5@suse.de>
Date: Fri, 20 Jun 2025 10:45:35 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Mario Limonciello <superm1@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Lukas Wunner <lukas@...ner.de>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, David Woodhouse <dwmw2@...radead.org>,
Lu Baolu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>,
Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
Alex Williamson <alex.williamson@...hat.com>,
Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
"open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
open list <linux-kernel@...r.kernel.org>,
"open list:INTEL IOMMU (VT-d)" <iommu@...ts.linux.dev>,
"open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
"open list:VFIO DRIVER" <kvm@...r.kernel.org>,
"open list:SOUND" <linux-sound@...r.kernel.org>,
Daniel Dadap <ddadap@...dia.com>,
Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH v3 6/7] PCI/VGA: Move check for firmware default out of
VGA arbiter
Hi
Am 20.06.25 um 04:49 schrieb Mario Limonciello:
> From: Mario Limonciello <mario.limonciello@....com>
>
> The x86 specific check for whether a framebuffer belongs to a device
> works for display devices as well as VGA devices. Callers to
> video_is_primary_device() can benefit from checking non-VGA display
> devices.
>
> Move the x86 specific check into x86 specific code, and adjust VGA
> arbiter to call that code as well. This allows fbcon to find the
> right PCI device on systems that don't have VGA devices.
>
> Suggested-by: Thomas Zimmermann <tzimmermann@...e.de>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
> arch/x86/video/video-common.c | 28 +++++++++++++++++++++++++++
> drivers/pci/vgaarb.c | 36 ++---------------------------------
> 2 files changed, 30 insertions(+), 34 deletions(-)
>
> diff --git a/arch/x86/video/video-common.c b/arch/x86/video/video-common.c
> index 81fc97a2a837a..718116e35e450 100644
> --- a/arch/x86/video/video-common.c
> +++ b/arch/x86/video/video-common.c
> @@ -9,6 +9,7 @@
>
> #include <linux/module.h>
> #include <linux/pci.h>
> +#include <linux/screen_info.h>
> #include <linux/vgaarb.h>
>
> #include <asm/video.h>
> @@ -27,13 +28,40 @@ EXPORT_SYMBOL(pgprot_framebuffer);
>
> bool video_is_primary_device(struct device *dev)
I'm not sure I understand this patch. video_is_primary_device() already
exists for 3 architectures, including x86. [1] Adding it here should
produce an error. (?)
[1] https://elixir.bootlin.com/linux/v6.15.2/A/ident/video_is_primary_device
The code on x86 is
bool
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/bool>video_is_primary_device
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/video_is_primary_device>(structdevice
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/device>*dev) {
structpci_dev
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/pci_dev>*pdev;
if(!dev_is_pci
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/dev_is_pci>(dev))
returnfalse <https://elixir.bootlin.com/linux/v6.15.2/C/ident/false>;
pdev=to_pci_dev
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/to_pci_dev>(dev);
return(pdev==vga_default_device
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/vga_default_device>()); }
I was thinking about extending it to test for additional properties,
like this
bool
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/bool>video_is_primary_device
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/video_is_primary_device>(structdevice
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/device>*dev) {
structpci_dev
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/pci_dev>*pdev;
if(!dev_is_pci
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/dev_is_pci>(dev))
returnfalse <https://elixir.bootlin.com/linux/v6.15.2/C/ident/false>;
pdev=to_pci_dev
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/to_pci_dev>(dev);
if(pdev==vga_default_device
<https://elixir.bootlin.com/linux/v6.15.2/C/ident/vga_default_device>())
return true for_each_pci_dev() { // test if display and could be
primary. } return false; // nothing found }
This would then be called from per-device sysfs code that export a
property similar to boot_vga (such as boot_display).
The issue is currently just an x86 problem, but I can imagine something
similar happening on ARM. There we'd have to go through the DT tree to
figure out the primary device. That's a problem for a later patch set,
but we should keep this in mind.
> {
> + u64 base = screen_info.lfb_base;
> + u64 size = screen_info.lfb_size;
> struct pci_dev *pdev;
> + struct resource *r;
> + u64 limit;
>
> if (!dev_is_pci(dev))
> return false;
>
> pdev = to_pci_dev(dev);
>
> + if (!pci_is_display(pdev))
> + return false;
> +
> + /* Select the device owning the boot framebuffer if there is one */
> + if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
> + base |= (u64)screen_info.ext_lfb_base << 32;
> +
> + limit = base + size;
> +
> + /* Does firmware framebuffer belong to us? */
> + pci_dev_for_each_resource(pdev, r) {
> + if (resource_type(r) != IORESOURCE_MEM)
> + continue;
> +
> + if (!r->start || !r->end)
> + continue;
> +
> + if (base < r->start || limit >= r->end)
> + continue;
> +
> + return true;
> + }
> +
You can drop all this code and call screen_info_pci_dev() instead. I
simply never got to update vgaarb to use it.
[2]
https://elixir.bootlin.com/linux/v6.15.2/source/drivers/video/screen_info_pci.c#L109
> return (pdev == vga_default_device());
> }
> EXPORT_SYMBOL(video_is_primary_device);
> diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
> index 78748e8d2dbae..15ab58c70b016 100644
> --- a/drivers/pci/vgaarb.c
> +++ b/drivers/pci/vgaarb.c
> @@ -26,12 +26,12 @@
> #include <linux/poll.h>
> #include <linux/miscdevice.h>
> #include <linux/slab.h>
> -#include <linux/screen_info.h>
> #include <linux/vt.h>
> #include <linux/console.h>
> #include <linux/acpi.h>
> #include <linux/uaccess.h>
> #include <linux/vgaarb.h>
> +#include <asm/video.h>
>
> static void vga_arbiter_notify_clients(void);
>
> @@ -554,38 +554,6 @@ void vga_put(struct pci_dev *pdev, unsigned int rsrc)
> }
> EXPORT_SYMBOL(vga_put);
>
> -static bool vga_is_firmware_default(struct pci_dev *pdev)
> -{
> -#if defined(CONFIG_X86)
> - u64 base = screen_info.lfb_base;
> - u64 size = screen_info.lfb_size;
> - struct resource *r;
> - u64 limit;
> -
> - /* Select the device owning the boot framebuffer if there is one */
> -
> - if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
> - base |= (u64)screen_info.ext_lfb_base << 32;
> -
> - limit = base + size;
> -
> - /* Does firmware framebuffer belong to us? */
> - pci_dev_for_each_resource(pdev, r) {
> - if (resource_type(r) != IORESOURCE_MEM)
> - continue;
> -
> - if (!r->start || !r->end)
> - continue;
> -
> - if (base < r->start || limit >= r->end)
> - continue;
> -
> - return true;
> - }
> -#endif
> - return false;
> -}
> -
> static bool vga_arb_integrated_gpu(struct device *dev)
> {
> #if defined(CONFIG_ACPI)
> @@ -623,7 +591,7 @@ static bool vga_is_boot_device(struct vga_device *vgadev)
> if (boot_vga && boot_vga->is_firmware_default)
> return false;
>
> - if (vga_is_firmware_default(pdev)) {
> + if (video_is_primary_device(&pdev->dev)) {
Maybe not change this because you don't want to end up with non-VGA
devices here.
Best regards
Thomas
> vgadev->is_firmware_default = true;
> return true;
> }
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
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