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DRM: Add a new 'boot_display' attribute

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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 the PCI device was used for driving the display.

Suggested-by: Manivannan Sadhasivam <mani@kernel.org>
Acked-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://gitlab.freedesktop.org/xorg/lib/libpciaccess/-/issues/23
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20250811162606.587759-5-superm1@kernel.org
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
This commit is contained in:
Mario Limonciello (AMD) 2025-08-11 11:26:06 -05:00
parent ad90860bd1
commit 7df7b728c3
2 changed files with 49 additions and 0 deletions
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8
Documentation/ABI/testing/sysfs-class-drm Normal file
View file

@ -0,0 +1,8 @@
What: /sys/class/drm/.../boot_display
Date: January 2026
Contact: Linux DRI developers <dri-devel@vger.kernel.org>
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".

41
drivers/gpu/drm/drm_sysfs.c
View file

@ -18,6 +18,7 @@
#include <linux/gfp.h>
#include <linux/i2c.h>
#include <linux/kdev_t.h>
#include <linux/pci.h>
#include <linux/property.h>
#include <linux/slab.h>
@ -30,6 +31,8 @@
#include <drm/drm_property.h>
#include <drm/drm_sysfs.h>
#include <asm/video.h>
#include "drm_internal.h"
#include "drm_crtc_internal.h"
@ -508,6 +511,43 @@ void drm_sysfs_connector_property_event(struct drm_connector *connector,
}
EXPORT_SYMBOL(drm_sysfs_connector_property_event);
static ssize_t boot_display_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
return sysfs_emit(buf, "1\n");
}
static DEVICE_ATTR_RO(boot_display);
static struct attribute *display_attrs[] = {
&dev_attr_boot_display.attr,
NULL
};
static umode_t boot_display_visible(struct kobject *kobj,
struct attribute *a, int n)
{
struct device *dev = kobj_to_dev(kobj)->parent;
if (dev_is_pci(dev)) {
struct pci_dev *pdev = to_pci_dev(dev);
if (video_is_primary_device(&pdev->dev))
return a->mode;
}
return 0;
}
static const struct attribute_group display_attr_group = {
.attrs = display_attrs,
.is_visible = boot_display_visible,
};
static const struct attribute_group *card_dev_groups[] = {
&display_attr_group,
NULL
};
struct device *drm_sysfs_minor_alloc(struct drm_minor *minor)
{
const char *minor_str;
@ -531,6 +571,7 @@ struct device *drm_sysfs_minor_alloc(struct drm_minor *minor)
kdev->devt = MKDEV(DRM_MAJOR, minor->index);
kdev->class = drm_class;
kdev->groups = card_dev_groups;
kdev->type = &drm_sysfs_device_minor;
}