Commit d1ff4b1c authored by Matthew Garrett's avatar Matthew Garrett Committed by Len Brown

ACPI: Add support for exposing BGRT data

ACPI 5.0 adds the BGRT, a table that contains a pointer to the firmware
boot splash and associated metadata. This simple driver exposes it via
/sys/firmware/acpi in order to allow bootsplash applications to draw their
splash around the firmware image and reduce the number of jarring graphical
transitions during boot.
Signed-off-by: default avatarMatthew Garrett <>
Signed-off-by: default avatarLen Brown <>
parent f2d4753f
What: /sys/firmware/acpi/bgrt/
Date: January 2012
Contact: Matthew Garrett <>
The BGRT is an ACPI 5.0 feature that allows the OS
to obtain a copy of the firmware boot splash and
some associated metadata. This is intended to be used
by boot splash applications in order to interact with
the firmware boot splash in order to avoid jarring
image: The image bitmap. Currently a 32-bit BMP.
status: 1 if the image is valid, 0 if firmware invalidated it.
type: 0 indicates image is in BMP format.
version: The version of the BGRT. Currently 1.
xoffset: The number of pixels between the left of the screen
and the left edge of the image.
yoffset: The number of pixels between the top of the screen
and the top edge of the image.
What: /sys/firmware/acpi/interrupts/
Date: February 2008
Contact: Len Brown <>
......@@ -384,6 +384,15 @@ config ACPI_CUSTOM_METHOD
load additional kernel modules after boot, this feature may be used
to override that restriction).
config ACPI_BGRT
tristate "Boottime Graphics Resource Table support"
default n
This driver adds support for exposing the ACPI Boottime Graphics
Resource Table, which allows the operating system to obtain
data from the firmware boot splash. It will appear under
/sys/firmware/acpi/bgrt/ .
source "drivers/acpi/apei/Kconfig"
endif # ACPI
......@@ -62,6 +62,7 @@ obj-$(CONFIG_ACPI_SBS) += sbs.o
obj-$(CONFIG_ACPI_HED) += hed.o
obj-$(CONFIG_ACPI_EC_DEBUGFS) += ec_sys.o
obj-$(CONFIG_ACPI_CUSTOM_METHOD)+= custom_method.o
obj-$(CONFIG_ACPI_BGRT) += bgrt.o
# processor has its own "processor." module_param namespace
processor-y := processor_driver.o processor_throttling.o
* Copyright 2012 Red Hat, Inc <>
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/sysfs.h>
#include <acpi/acpi.h>
#include <acpi/acpi_bus.h>
static struct acpi_table_bgrt *bgrt_tab;
static struct kobject *bgrt_kobj;
struct bmp_header {
u16 id;
u32 size;
} __attribute ((packed));
static struct bmp_header bmp_header;
static ssize_t show_version(struct device *dev,
struct device_attribute *attr, char *buf)
return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->version);
static DEVICE_ATTR(version, S_IRUGO, show_version, NULL);
static ssize_t show_status(struct device *dev,
struct device_attribute *attr, char *buf)
return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->status);
static DEVICE_ATTR(status, S_IRUGO, show_status, NULL);
static ssize_t show_type(struct device *dev,
struct device_attribute *attr, char *buf)
return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->image_type);
static DEVICE_ATTR(type, S_IRUGO, show_type, NULL);
static ssize_t show_xoffset(struct device *dev,
struct device_attribute *attr, char *buf)
return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->image_offset_x);
static DEVICE_ATTR(xoffset, S_IRUGO, show_xoffset, NULL);
static ssize_t show_yoffset(struct device *dev,
struct device_attribute *attr, char *buf)
return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->image_offset_y);
static DEVICE_ATTR(yoffset, S_IRUGO, show_yoffset, NULL);
static ssize_t show_image(struct file *file, struct kobject *kobj,
struct bin_attribute *attr, char *buf, loff_t off, size_t count)
int size = attr->size;
void __iomem *image = attr->private;
if (off >= size) {
count = 0;
} else {
if (off + count > size)
count = size - off;
memcpy_fromio(buf, image+off, count);
return count;
static struct bin_attribute image_attr = {
.attr = {
.name = "image",
.mode = S_IRUGO,
.read = show_image,
static struct attribute *bgrt_attributes[] = {
static struct attribute_group bgrt_attribute_group = {
.attrs = bgrt_attributes,
static int __init bgrt_init(void)
acpi_status status;
int ret;
void __iomem *bgrt;
if (acpi_disabled)
return -ENODEV;
status = acpi_get_table("BGRT", 0,
(struct acpi_table_header **)&bgrt_tab);
if (ACPI_FAILURE(status))
return -ENODEV;
bgrt = ioremap(bgrt_tab->image_address, sizeof(struct bmp_header));
if (!bgrt) {
ret = -EINVAL;
goto out_err;
memcpy_fromio(&bmp_header, bgrt, sizeof(bmp_header));
image_attr.size = bmp_header.size;
image_attr.private = ioremap(bgrt_tab->image_address, image_attr.size);
if (!image_attr.private) {
ret = -EINVAL;
goto out_err;
bgrt_kobj = kobject_create_and_add("bgrt", acpi_kobj);
if (!bgrt_kobj) {
ret = -EINVAL;
goto out_iounmap;
ret = sysfs_create_group(bgrt_kobj, &bgrt_attribute_group);
if (ret)
goto out_kobject;
ret = sysfs_create_bin_file(bgrt_kobj, &image_attr);
if (ret)
goto out_group;
return 0;
sysfs_remove_group(bgrt_kobj, &bgrt_attribute_group);
return ret;
static void __exit bgrt_exit(void)
sysfs_remove_group(bgrt_kobj, &bgrt_attribute_group);
sysfs_remove_bin_file(bgrt_kobj, &image_attr);
MODULE_AUTHOR("Matthew Garrett");
MODULE_DESCRIPTION("BGRT boot graphic support");
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