From: Mario Limonciello <[email protected]> On systems with multiple GPUs there can be uncertainty which GPU is the primary one used to drive the display at bootup. 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.
Signed-off-by: Mario Limonciello <[email protected]> --- v4: * new patch --- Documentation/ABI/testing/sysfs-bus-pci | 9 +++++++++ drivers/pci/pci-sysfs.c | 14 ++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index 69f952fffec72..2e6f85fbe2e2e 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -612,3 +612,12 @@ Description: # ls doe_features 0001:01 0001:02 doe_discovery + +What: /sys/bus/pci/devices/.../boot_display +Date: October 2025 +Contact: Linux PCI developers <[email protected]> +Description: + This file indicates whether the device was used as a boot + display. If the device was used as the boot display, the file + will contain "1". If the device is a display device but wasn't + used as a boot display, the file will contain "0". diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 268c69daa4d57..5bbf79b1b953d 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -30,6 +30,7 @@ #include <linux/msi.h> #include <linux/of.h> #include <linux/aperture.h> +#include <asm/video.h> #include "pci.h" #ifndef ARCH_PCI_DEV_GROUPS @@ -679,6 +680,13 @@ const struct attribute_group *pcibus_groups[] = { NULL, }; +static ssize_t boot_display_show(struct device *dev, struct device_attribute *attr, + char *buf) +{ + return sysfs_emit(buf, "%u\n", video_is_primary_device(dev)); +} +static DEVICE_ATTR_RO(boot_display); + static ssize_t boot_vga_show(struct device *dev, struct device_attribute *attr, char *buf) { @@ -1698,6 +1706,7 @@ late_initcall(pci_sysfs_init); static struct attribute *pci_dev_dev_attrs[] = { &dev_attr_boot_vga.attr, + &dev_attr_boot_display.attr, NULL, }; @@ -1710,6 +1719,11 @@ static umode_t pci_dev_attrs_are_visible(struct kobject *kobj, if (a == &dev_attr_boot_vga.attr && pci_is_vga(pdev)) return a->mode; +#ifdef CONFIG_VIDEO + if (a == &dev_attr_boot_display.attr && pci_is_display(pdev)) + return a->mode; +#endif + return 0; } -- 2.43.0
