blob: f3f0fe7e255a23ef679f718324cbf9e2f16e3f31 [file] [log] [blame]
* Copyright (C) 2008 SuSE Linux Products GmbH
* Thomas Renninger <>
* May be copied or modified under the terms of the GNU General Public License
* video_detect.c:
* Provides acpi_is_video_device() for early scanning of ACPI devices in scan.c
* There a Linux specific (Spec does not provide a HID for video devices) is
* assigned
* After PCI devices are glued with ACPI devices
* acpi_get_pci_dev() can be called to identify ACPI graphics
* devices for which a real graphics card is plugged in
* Now acpi_video_get_capabilities() can be called to check which
* capabilities the graphics cards plugged in support. The check for general
* video capabilities will be triggered by the first caller of
* acpi_video_get_capabilities(NULL); which will happen when the first
* backlight switching supporting driver calls:
* acpi_video_backlight_support();
* Depending on whether ACPI graphics extensions (cmp. ACPI spec Appendix B)
* are available, video.ko should be used to handle the device.
* Otherwise vendor specific drivers like thinkpad_acpi, asus_acpi,
* sony_acpi,... can take care about backlight brightness.
* If CONFIG_ACPI_VIDEO is neither set as "compiled in" (y) nor as a module (m)
* this file will not be compiled, acpi_video_get_capabilities() and
* acpi_video_backlight_support() will always return 0 and vendor specific
* drivers always can handle backlight.
#include <linux/export.h>
#include <linux/acpi.h>
#include <linux/dmi.h>
#include <linux/pci.h>
#define PREFIX "ACPI: "
static long acpi_video_support;
static bool acpi_video_caps_checked;
static acpi_status
acpi_backlight_cap_match(acpi_handle handle, u32 level, void *context,
void **retyurn_value)
long *cap = context;
acpi_handle h_dummy;
if (ACPI_SUCCESS(acpi_get_handle(handle, "_BCM", &h_dummy)) &&
ACPI_SUCCESS(acpi_get_handle(handle, "_BCL", &h_dummy))) {
ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Found generic backlight "
if (ACPI_FAILURE(acpi_get_handle(handle, "_BQC", &h_dummy)))
printk(KERN_WARNING FW_BUG PREFIX "No _BQC method, "
"cannot determine initial brightness\n");
/* We have backlight support, no need to scan further */
return 0;
/* Returns true if the device is a video device which can be handled by
* video.ko.
* The device will get a Linux specific CID added in scan.c to
* identify the device as an ACPI graphics device
* Be aware that the graphics device may not be physically present
* Use acpi_video_get_capabilities() to detect general ACPI video
* capabilities of present cards
long acpi_is_video_device(struct acpi_device *device)
acpi_handle h_dummy;
long video_caps = 0;
if (!device)
return 0;
/* Is this device able to support video switching ? */
if (ACPI_SUCCESS(acpi_get_handle(device->handle, "_DOD", &h_dummy)) ||
ACPI_SUCCESS(acpi_get_handle(device->handle, "_DOS", &h_dummy)))
/* Is this device able to retrieve a video ROM ? */
if (ACPI_SUCCESS(acpi_get_handle(device->handle, "_ROM", &h_dummy)))
/* Is this device able to configure which video head to be POSTed ? */
if (ACPI_SUCCESS(acpi_get_handle(device->handle, "_VPO", &h_dummy)) &&
ACPI_SUCCESS(acpi_get_handle(device->handle, "_GPD", &h_dummy)) &&
ACPI_SUCCESS(acpi_get_handle(device->handle, "_SPD", &h_dummy)))
/* Only check for backlight functionality if one of the above hit. */
if (video_caps)
acpi_walk_namespace(ACPI_TYPE_DEVICE, device->handle,
ACPI_UINT32_MAX, acpi_backlight_cap_match, NULL,
&video_caps, NULL);
return video_caps;
static acpi_status
find_video(acpi_handle handle, u32 lvl, void *context, void **rv)
long *cap = context;
struct pci_dev *dev;
struct acpi_device *acpi_dev;
const struct acpi_device_id video_ids[] = {
{"", 0},
if (acpi_bus_get_device(handle, &acpi_dev))
return AE_OK;
if (!acpi_match_device_ids(acpi_dev, video_ids)) {
dev = acpi_get_pci_dev(handle);
if (!dev)
return AE_OK;
*cap |= acpi_is_video_device(acpi_dev);
return AE_OK;
* Returns the video capabilities of a specific ACPI graphics device
* if NULL is passed as argument all ACPI devices are enumerated and
* all graphics capabilities of physically present devices are
* summarized and returned. This is cached and done only once.
long acpi_video_get_capabilities(acpi_handle graphics_handle)
long caps = 0;
struct acpi_device *tmp_dev;
acpi_status status;
if (acpi_video_caps_checked && graphics_handle == NULL)
return acpi_video_support;
if (!graphics_handle) {
/* Only do the global walk through all graphics devices once */
ACPI_UINT32_MAX, find_video, NULL,
&caps, NULL);
/* There might be boot param flags set already... */
acpi_video_support |= caps;
acpi_video_caps_checked = 1;
/* Add blacklists here. Be careful to use the right *DMI* bits
* to still be able to override logic via boot params, e.g.:
* if (dmi_name_in_vendors("XY")) {
* acpi_video_support |=
} else {
status = acpi_bus_get_device(graphics_handle, &tmp_dev);
if (ACPI_FAILURE(status)) {
ACPI_EXCEPTION((AE_INFO, status, "Invalid device"));
return 0;
acpi_walk_namespace(ACPI_TYPE_DEVICE, graphics_handle,
ACPI_UINT32_MAX, find_video, NULL,
&caps, NULL);
ACPI_DEBUG_PRINT((ACPI_DB_INFO, "We have 0x%lX video support %s %s\n",
graphics_handle ? caps : acpi_video_support,
graphics_handle ? "on device " : "in general",
graphics_handle ? acpi_device_bid(tmp_dev) : ""));
return caps;
/* Returns true if video.ko can do backlight switching */
int acpi_video_backlight_support(void)
* We must check whether the ACPI graphics device is physically plugged
* in. Therefore this must be called after binding PCI and ACPI devices
if (!acpi_video_caps_checked)
/* First check for boot param -> highest prio */
if (acpi_video_support & ACPI_VIDEO_BACKLIGHT_FORCE_VENDOR)
return 0;
else if (acpi_video_support & ACPI_VIDEO_BACKLIGHT_FORCE_VIDEO)
return 1;
/* Then check for DMI blacklist -> second highest prio */
if (acpi_video_support & ACPI_VIDEO_BACKLIGHT_DMI_VENDOR)
return 0;
else if (acpi_video_support & ACPI_VIDEO_BACKLIGHT_DMI_VIDEO)
return 1;
/* Then go the default way */
return acpi_video_support & ACPI_VIDEO_BACKLIGHT;
* Use acpi_backlight=vendor/video to force that backlight switching
* is processed by vendor specific acpi drivers or video.ko driver.
static int __init acpi_backlight(char *str)
if (str == NULL || *str == '\0')
return 1;
else {
if (!strcmp("vendor", str))
acpi_video_support |=
if (!strcmp("video", str))
acpi_video_support |=
return 1;
__setup("acpi_backlight=", acpi_backlight);