On Tue, Jun 24, 2025 at 03:30:42PM -0500, Mario Limonciello wrote: > 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]>
Acked-by: Bjorn Helgaas <[email protected]> Question below. > --- > 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..897cfc1b0de0f 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". Is there a reason to expose this file if it wasn't a boot display device? Maybe it doesn't need to exist at all unless it contains "1"? > 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 >
