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linux/drivers/acpi/video_detect.c

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/*
* Copyright (C) 2015 Red Hat Inc.
* Hans de Goede <hdegoede@redhat.com>
* Copyright (C) 2008 SuSE Linux Products GmbH
* Thomas Renninger <trenn@suse.de>
*
* May be copied or modified under the terms of the GNU General Public License
*
* video_detect.c:
* 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
*
* 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-laptop,
* sony_acpi,... can take care about backlight brightness.
*
* Backlight drivers can use acpi_video_get_backlight_type() to determine
* which driver should handle the backlight.
*
* If CONFIG_ACPI_VIDEO is neither set as "compiled in" (y) nor as a module (m)
* this file will not be compiled and acpi_video_get_backlight_type() will
* always return acpi_backlight_vendor.
*/
#include <linux/export.h>
#include <linux/acpi.h>
#include <linux/backlight.h>
#include <linux/dmi.h>
acpi-video-detect: video: Make video_detect code part of the video module This is a preparation patch for the backlight interface selection logic cleanup, there are 2 reasons to not always build the video_detect code into the kernel: 1) In order for the video_detect.c to also deal with / select native backlight interfaces on win8 systems, instead of doing this in video.c where it does not belong, video_detect.c needs to call into the backlight class code. Which cannot be done if it is builtin and the blacklight class is not. 2) Currently all the platform/x86 drivers which have quirks to prefer the vendor driver over acpi-video call acpi_video_unregister_backlight() to remove the acpi-video backlight interface, this logic really belongs in video_detect.c, which will cause video_detect.c to depend on symbols of video.c and video.c already depends on video_detect.c symbols, so they really need to be a single module. Note that this commits make 2 changes so as to maintain 100% kernel commandline compatibility: 1) The __setup call for the acpi_backlight= handling is moved to acpi/util.c as __setup may only be used by code which is alwasy builtin 2) video.c is renamed to acpi_video.c so that it can be combined with video_detect.c into video.ko This commit also makes changes to drivers/platform/x86/Kconfig to ensure that drivers which use acpi_video_backlight_support() from video_detect.c, will not be built-in when acpi_video is not built in. This also changes some "select" uses to "depends on" to avoid dependency loops. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Darren Hart <dvhart@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-06-16 14:27:47 +00:00
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/types.h>
ACPI / video: Fix circular lock dependency issue in the video-detect code Before this commit, the following would happen: a) acpi_video_get_backlight_type() gets called b) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type() c) acpi_video_init_backlight_type() locks its function static init_mutex d) acpi_video_init_backlight_type() calls backlight_register_notifier() e) backlight_register_notifier() takes its notifier-chain lock And when the backlight notifier chain gets called we've: 1) blocking_notifier_call_chain() gets called 2) blocking_notifier_call_chain() takes the notifier-chain lock 3) blocking_notifier_call_chain() calls acpi_video_backlight_notify() 4) acpi_video_backlight_notify() calls acpi_video_get_backlight_type() 5) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type() 6) acpi_video_init_backlight_type() locks its function static init_mutex So in the first call sequence we have: a) init_mutex gets locked b) notifier-chain gets locked and in the second call sequence we have: 1) notifier-chain gets locked 2) init_mutex gets locked And we've a circular locking dependency. This specific locking dependency is fixable without using the big hammer otherwise known as a workqueue, but further analysis shows a similar problem with the backlight notifier chain lock vs register_count_mutex from drivers/acpi/acpi_video.c, and fixing that becomes problematic. So this commit simply fixes this with the big hammer, performance wise this is a non issue as we expect the work to get scheduled exactly zero or one times during normal system use. Fixes: 93a291dfaf9c (ACPI / video: Move backlight notifier to video_detect.c) Signed-off-by: Hans de Goede <hdegoede@redhat.com> Reported-and-tested-by: Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-08-13 16:53:37 +00:00
#include <linux/workqueue.h>
#include <acpi/video.h>
void acpi_video_unregister_backlight(void);
static bool backlight_notifier_registered;
static struct notifier_block backlight_nb;
ACPI / video: Fix circular lock dependency issue in the video-detect code Before this commit, the following would happen: a) acpi_video_get_backlight_type() gets called b) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type() c) acpi_video_init_backlight_type() locks its function static init_mutex d) acpi_video_init_backlight_type() calls backlight_register_notifier() e) backlight_register_notifier() takes its notifier-chain lock And when the backlight notifier chain gets called we've: 1) blocking_notifier_call_chain() gets called 2) blocking_notifier_call_chain() takes the notifier-chain lock 3) blocking_notifier_call_chain() calls acpi_video_backlight_notify() 4) acpi_video_backlight_notify() calls acpi_video_get_backlight_type() 5) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type() 6) acpi_video_init_backlight_type() locks its function static init_mutex So in the first call sequence we have: a) init_mutex gets locked b) notifier-chain gets locked and in the second call sequence we have: 1) notifier-chain gets locked 2) init_mutex gets locked And we've a circular locking dependency. This specific locking dependency is fixable without using the big hammer otherwise known as a workqueue, but further analysis shows a similar problem with the backlight notifier chain lock vs register_count_mutex from drivers/acpi/acpi_video.c, and fixing that becomes problematic. So this commit simply fixes this with the big hammer, performance wise this is a non issue as we expect the work to get scheduled exactly zero or one times during normal system use. Fixes: 93a291dfaf9c (ACPI / video: Move backlight notifier to video_detect.c) Signed-off-by: Hans de Goede <hdegoede@redhat.com> Reported-and-tested-by: Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-08-13 16:53:37 +00:00
static struct work_struct backlight_notify_work;
static enum acpi_backlight_type acpi_backlight_cmdline = acpi_backlight_undef;
static enum acpi_backlight_type acpi_backlight_dmi = acpi_backlight_undef;
acpi-video-detect: video: Make video_detect code part of the video module This is a preparation patch for the backlight interface selection logic cleanup, there are 2 reasons to not always build the video_detect code into the kernel: 1) In order for the video_detect.c to also deal with / select native backlight interfaces on win8 systems, instead of doing this in video.c where it does not belong, video_detect.c needs to call into the backlight class code. Which cannot be done if it is builtin and the blacklight class is not. 2) Currently all the platform/x86 drivers which have quirks to prefer the vendor driver over acpi-video call acpi_video_unregister_backlight() to remove the acpi-video backlight interface, this logic really belongs in video_detect.c, which will cause video_detect.c to depend on symbols of video.c and video.c already depends on video_detect.c symbols, so they really need to be a single module. Note that this commits make 2 changes so as to maintain 100% kernel commandline compatibility: 1) The __setup call for the acpi_backlight= handling is moved to acpi/util.c as __setup may only be used by code which is alwasy builtin 2) video.c is renamed to acpi_video.c so that it can be combined with video_detect.c into video.ko This commit also makes changes to drivers/platform/x86/Kconfig to ensure that drivers which use acpi_video_backlight_support() from video_detect.c, will not be built-in when acpi_video is not built in. This also changes some "select" uses to "depends on" to avoid dependency loops. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Darren Hart <dvhart@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-06-16 14:27:47 +00:00
static void acpi_video_parse_cmdline(void)
{
if (!strcmp("vendor", acpi_video_backlight_string))
acpi_backlight_cmdline = acpi_backlight_vendor;
acpi-video-detect: video: Make video_detect code part of the video module This is a preparation patch for the backlight interface selection logic cleanup, there are 2 reasons to not always build the video_detect code into the kernel: 1) In order for the video_detect.c to also deal with / select native backlight interfaces on win8 systems, instead of doing this in video.c where it does not belong, video_detect.c needs to call into the backlight class code. Which cannot be done if it is builtin and the blacklight class is not. 2) Currently all the platform/x86 drivers which have quirks to prefer the vendor driver over acpi-video call acpi_video_unregister_backlight() to remove the acpi-video backlight interface, this logic really belongs in video_detect.c, which will cause video_detect.c to depend on symbols of video.c and video.c already depends on video_detect.c symbols, so they really need to be a single module. Note that this commits make 2 changes so as to maintain 100% kernel commandline compatibility: 1) The __setup call for the acpi_backlight= handling is moved to acpi/util.c as __setup may only be used by code which is alwasy builtin 2) video.c is renamed to acpi_video.c so that it can be combined with video_detect.c into video.ko This commit also makes changes to drivers/platform/x86/Kconfig to ensure that drivers which use acpi_video_backlight_support() from video_detect.c, will not be built-in when acpi_video is not built in. This also changes some "select" uses to "depends on" to avoid dependency loops. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Darren Hart <dvhart@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-06-16 14:27:47 +00:00
if (!strcmp("video", acpi_video_backlight_string))
acpi_backlight_cmdline = acpi_backlight_video;
if (!strcmp("native", acpi_video_backlight_string))
acpi_backlight_cmdline = acpi_backlight_native;
if (!strcmp("none", acpi_video_backlight_string))
acpi_backlight_cmdline = acpi_backlight_none;
acpi-video-detect: video: Make video_detect code part of the video module This is a preparation patch for the backlight interface selection logic cleanup, there are 2 reasons to not always build the video_detect code into the kernel: 1) In order for the video_detect.c to also deal with / select native backlight interfaces on win8 systems, instead of doing this in video.c where it does not belong, video_detect.c needs to call into the backlight class code. Which cannot be done if it is builtin and the blacklight class is not. 2) Currently all the platform/x86 drivers which have quirks to prefer the vendor driver over acpi-video call acpi_video_unregister_backlight() to remove the acpi-video backlight interface, this logic really belongs in video_detect.c, which will cause video_detect.c to depend on symbols of video.c and video.c already depends on video_detect.c symbols, so they really need to be a single module. Note that this commits make 2 changes so as to maintain 100% kernel commandline compatibility: 1) The __setup call for the acpi_backlight= handling is moved to acpi/util.c as __setup may only be used by code which is alwasy builtin 2) video.c is renamed to acpi_video.c so that it can be combined with video_detect.c into video.ko This commit also makes changes to drivers/platform/x86/Kconfig to ensure that drivers which use acpi_video_backlight_support() from video_detect.c, will not be built-in when acpi_video is not built in. This also changes some "select" uses to "depends on" to avoid dependency loops. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Darren Hart <dvhart@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-06-16 14:27:47 +00:00
}
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;
static const struct acpi_device_id video_ids[] = {
{ACPI_VIDEO_HID, 0},
{"", 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;
pci_dev_put(dev);
*cap |= acpi_is_video_device(handle);
}
return AE_OK;
}
/* Force to use vendor driver when the ACPI device is known to be
* buggy */
static int video_detect_force_vendor(const struct dmi_system_id *d)
{
acpi_backlight_dmi = acpi_backlight_vendor;
return 0;
}
static int video_detect_force_video(const struct dmi_system_id *d)
{
acpi_backlight_dmi = acpi_backlight_video;
return 0;
}
static int video_detect_force_native(const struct dmi_system_id *d)
{
acpi_backlight_dmi = acpi_backlight_native;
return 0;
}
static int video_detect_force_none(const struct dmi_system_id *d)
{
acpi_backlight_dmi = acpi_backlight_none;
return 0;
}
static const struct dmi_system_id video_detect_dmi_table[] = {
/* On Samsung X360, the BIOS will set a flag (VDRV) if generic
* ACPI backlight device is used. This flag will definitively break
* the backlight interface (even the vendor interface) until next
* reboot. It's why we should prevent video.ko from being used here
* and we can't rely on a later call to acpi_video_unregister().
*/
{
.callback = video_detect_force_vendor,
.ident = "X360",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
DMI_MATCH(DMI_PRODUCT_NAME, "X360"),
DMI_MATCH(DMI_BOARD_NAME, "X360"),
},
},
{
.callback = video_detect_force_vendor,
.ident = "Asus UL30VT",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
DMI_MATCH(DMI_PRODUCT_NAME, "UL30VT"),
},
},
{
.callback = video_detect_force_vendor,
.ident = "Asus UL30A",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
DMI_MATCH(DMI_PRODUCT_NAME, "UL30A"),
},
},
{
.callback = video_detect_force_vendor,
.ident = "GIGABYTE GB-BXBT-2807",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "GIGABYTE"),
DMI_MATCH(DMI_PRODUCT_NAME, "GB-BXBT-2807"),
},
},
{
.ident = "Sony VPCEH3U1E",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
DMI_MATCH(DMI_PRODUCT_NAME, "VPCEH3U1E"),
},
},
/*
* These models have a working acpi_video backlight control, and using
* native backlight causes a regression where backlight does not work
* when userspace is not handling brightness key events. Disable
* native_backlight on these to fix this:
* https://bugzilla.kernel.org/show_bug.cgi?id=81691
*/
{
.callback = video_detect_force_video,
.ident = "ThinkPad T420",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T420"),
},
},
{
.callback = video_detect_force_video,
.ident = "ThinkPad T520",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T520"),
},
},
{
.callback = video_detect_force_video,
.ident = "ThinkPad X201s",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201s"),
},
},
{
.callback = video_detect_force_video,
.ident = "ThinkPad X201T",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201T"),
},
},
/* The native backlight controls do not work on some older machines */
{
/* https://bugs.freedesktop.org/show_bug.cgi?id=81515 */
.callback = video_detect_force_video,
.ident = "HP ENVY 15 Notebook",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
DMI_MATCH(DMI_PRODUCT_NAME, "HP ENVY 15 Notebook PC"),
},
},
{
.callback = video_detect_force_video,
.ident = "SAMSUNG 870Z5E/880Z5E/680Z5E",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
DMI_MATCH(DMI_PRODUCT_NAME, "870Z5E/880Z5E/680Z5E"),
},
},
{
.callback = video_detect_force_video,
.ident = "SAMSUNG 370R4E/370R4V/370R5E/3570RE/370R5V",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
DMI_MATCH(DMI_PRODUCT_NAME,
"370R4E/370R4V/370R5E/3570RE/370R5V"),
},
},
{
/* https://bugzilla.redhat.com/show_bug.cgi?id=1186097 */
.callback = video_detect_force_video,
.ident = "SAMSUNG 3570R/370R/470R/450R/510R/4450RV",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
DMI_MATCH(DMI_PRODUCT_NAME,
"3570R/370R/470R/450R/510R/4450RV"),
},
},
{
/* https://bugzilla.redhat.com/show_bug.cgi?id=1557060 */
.callback = video_detect_force_video,
.ident = "SAMSUNG 670Z5E",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
DMI_MATCH(DMI_PRODUCT_NAME, "670Z5E"),
},
},
{
/* https://bugzilla.redhat.com/show_bug.cgi?id=1094948 */
.callback = video_detect_force_video,
.ident = "SAMSUNG 730U3E/740U3E",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
DMI_MATCH(DMI_PRODUCT_NAME, "730U3E/740U3E"),
},
},
{
/* https://bugs.freedesktop.org/show_bug.cgi?id=87286 */
.callback = video_detect_force_video,
.ident = "SAMSUNG 900X3C/900X3D/900X3E/900X4C/900X4D",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
DMI_MATCH(DMI_PRODUCT_NAME,
"900X3C/900X3D/900X3E/900X4C/900X4D"),
},
},
{
/* https://bugzilla.redhat.com/show_bug.cgi?id=1272633 */
.callback = video_detect_force_video,
.ident = "Dell XPS14 L421X",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
DMI_MATCH(DMI_PRODUCT_NAME, "XPS L421X"),
},
},
{
/* https://bugzilla.redhat.com/show_bug.cgi?id=1163574 */
.callback = video_detect_force_video,
.ident = "Dell XPS15 L521X",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
DMI_MATCH(DMI_PRODUCT_NAME, "XPS L521X"),
},
},
{
/* https://bugzilla.kernel.org/show_bug.cgi?id=108971 */
.callback = video_detect_force_video,
.ident = "SAMSUNG 530U4E/540U4E",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
DMI_MATCH(DMI_PRODUCT_NAME, "530U4E/540U4E"),
},
},
/* https://bugs.launchpad.net/bugs/1894667 */
{
.callback = video_detect_force_video,
.ident = "HP 635 Notebook",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
DMI_MATCH(DMI_PRODUCT_NAME, "HP 635 Notebook PC"),
},
},
/* Non win8 machines which need native backlight nevertheless */
{
/* https://bugzilla.redhat.com/show_bug.cgi?id=1201530 */
.callback = video_detect_force_native,
.ident = "Lenovo Ideapad S405",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
DMI_MATCH(DMI_BOARD_NAME, "Lenovo IdeaPad S405"),
},
},
{
/* https://bugzilla.redhat.com/show_bug.cgi?id=1187004 */
.callback = video_detect_force_native,
.ident = "Lenovo Ideapad Z570",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
DMI_MATCH(DMI_PRODUCT_NAME, "102434U"),
},
},
{
.callback = video_detect_force_native,
.ident = "Lenovo E41-25",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
DMI_MATCH(DMI_PRODUCT_NAME, "81FS"),
},
},
{
.callback = video_detect_force_native,
.ident = "Lenovo E41-45",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
DMI_MATCH(DMI_PRODUCT_NAME, "82BK"),
},
},
{
/* https://bugzilla.redhat.com/show_bug.cgi?id=1217249 */
.callback = video_detect_force_native,
.ident = "Apple MacBook Pro 12,1",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro12,1"),
},
},
{
.callback = video_detect_force_native,
.ident = "Dell Vostro V131",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V131"),
},
},
{
/* https://bugzilla.redhat.com/show_bug.cgi?id=1123661 */
.callback = video_detect_force_native,
.ident = "Dell XPS 17 L702X",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
DMI_MATCH(DMI_PRODUCT_NAME, "Dell System XPS L702X"),
},
},
{
.callback = video_detect_force_native,
.ident = "Dell Precision 7510",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
DMI_MATCH(DMI_PRODUCT_NAME, "Precision 7510"),
},
},
{
.callback = video_detect_force_native,
.ident = "Acer Aspire 5738z",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5738"),
DMI_MATCH(DMI_BOARD_NAME, "JV50"),
},
},
{
/* https://bugzilla.kernel.org/show_bug.cgi?id=207835 */
.callback = video_detect_force_native,
.ident = "Acer TravelMate 5735Z",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 5735Z"),
DMI_MATCH(DMI_BOARD_NAME, "BA51_MV"),
},
},
/*
* Desktops which falsely report a backlight and which our heuristics
* for this do not catch.
*/
{
.callback = video_detect_force_none,
.ident = "Dell OptiPlex 9020M",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 9020M"),
},
},
{
.callback = video_detect_force_none,
.ident = "MSI MS-7721",
.matches = {
DMI_MATCH(DMI_SYS_VENDOR, "MSI"),
DMI_MATCH(DMI_PRODUCT_NAME, "MS-7721"),
},
},
{ },
};
ACPI / video: Fix circular lock dependency issue in the video-detect code Before this commit, the following would happen: a) acpi_video_get_backlight_type() gets called b) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type() c) acpi_video_init_backlight_type() locks its function static init_mutex d) acpi_video_init_backlight_type() calls backlight_register_notifier() e) backlight_register_notifier() takes its notifier-chain lock And when the backlight notifier chain gets called we've: 1) blocking_notifier_call_chain() gets called 2) blocking_notifier_call_chain() takes the notifier-chain lock 3) blocking_notifier_call_chain() calls acpi_video_backlight_notify() 4) acpi_video_backlight_notify() calls acpi_video_get_backlight_type() 5) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type() 6) acpi_video_init_backlight_type() locks its function static init_mutex So in the first call sequence we have: a) init_mutex gets locked b) notifier-chain gets locked and in the second call sequence we have: 1) notifier-chain gets locked 2) init_mutex gets locked And we've a circular locking dependency. This specific locking dependency is fixable without using the big hammer otherwise known as a workqueue, but further analysis shows a similar problem with the backlight notifier chain lock vs register_count_mutex from drivers/acpi/acpi_video.c, and fixing that becomes problematic. So this commit simply fixes this with the big hammer, performance wise this is a non issue as we expect the work to get scheduled exactly zero or one times during normal system use. Fixes: 93a291dfaf9c (ACPI / video: Move backlight notifier to video_detect.c) Signed-off-by: Hans de Goede <hdegoede@redhat.com> Reported-and-tested-by: Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-08-13 16:53:37 +00:00
/* This uses a workqueue to avoid various locking ordering issues */
static void acpi_video_backlight_notify_work(struct work_struct *work)
{
if (acpi_video_get_backlight_type() != acpi_backlight_video)
acpi_video_unregister_backlight();
}
static int acpi_video_backlight_notify(struct notifier_block *nb,
unsigned long val, void *bd)
{
struct backlight_device *backlight = bd;
/* A raw bl registering may change video -> native */
if (backlight->props.type == BACKLIGHT_RAW &&
ACPI / video: Fix circular lock dependency issue in the video-detect code Before this commit, the following would happen: a) acpi_video_get_backlight_type() gets called b) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type() c) acpi_video_init_backlight_type() locks its function static init_mutex d) acpi_video_init_backlight_type() calls backlight_register_notifier() e) backlight_register_notifier() takes its notifier-chain lock And when the backlight notifier chain gets called we've: 1) blocking_notifier_call_chain() gets called 2) blocking_notifier_call_chain() takes the notifier-chain lock 3) blocking_notifier_call_chain() calls acpi_video_backlight_notify() 4) acpi_video_backlight_notify() calls acpi_video_get_backlight_type() 5) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type() 6) acpi_video_init_backlight_type() locks its function static init_mutex So in the first call sequence we have: a) init_mutex gets locked b) notifier-chain gets locked and in the second call sequence we have: 1) notifier-chain gets locked 2) init_mutex gets locked And we've a circular locking dependency. This specific locking dependency is fixable without using the big hammer otherwise known as a workqueue, but further analysis shows a similar problem with the backlight notifier chain lock vs register_count_mutex from drivers/acpi/acpi_video.c, and fixing that becomes problematic. So this commit simply fixes this with the big hammer, performance wise this is a non issue as we expect the work to get scheduled exactly zero or one times during normal system use. Fixes: 93a291dfaf9c (ACPI / video: Move backlight notifier to video_detect.c) Signed-off-by: Hans de Goede <hdegoede@redhat.com> Reported-and-tested-by: Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-08-13 16:53:37 +00:00
val == BACKLIGHT_REGISTERED)
schedule_work(&backlight_notify_work);
return NOTIFY_OK;
}
/*
* Determine which type of backlight interface to use on this system,
* First check cmdline, then dmi quirks, then do autodetect.
*
* The autodetect order is:
* 1) Is the acpi-video backlight interface supported ->
* no, use a vendor interface
* 2) Is this a win8 "ready" BIOS and do we have a native interface ->
* yes, use a native interface
* 3) Else use the acpi-video interface
*
* Arguably the native on win8 check should be done first, but that would
* be a behavior change, which may causes issues.
*/
enum acpi_backlight_type acpi_video_get_backlight_type(void)
{
static DEFINE_MUTEX(init_mutex);
static bool init_done;
static long video_caps;
/* Parse cmdline, dmi and acpi only once */
mutex_lock(&init_mutex);
if (!init_done) {
acpi_video_parse_cmdline();
dmi_check_system(video_detect_dmi_table);
acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
ACPI_UINT32_MAX, find_video, NULL,
&video_caps, NULL);
ACPI / video: Fix circular lock dependency issue in the video-detect code Before this commit, the following would happen: a) acpi_video_get_backlight_type() gets called b) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type() c) acpi_video_init_backlight_type() locks its function static init_mutex d) acpi_video_init_backlight_type() calls backlight_register_notifier() e) backlight_register_notifier() takes its notifier-chain lock And when the backlight notifier chain gets called we've: 1) blocking_notifier_call_chain() gets called 2) blocking_notifier_call_chain() takes the notifier-chain lock 3) blocking_notifier_call_chain() calls acpi_video_backlight_notify() 4) acpi_video_backlight_notify() calls acpi_video_get_backlight_type() 5) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type() 6) acpi_video_init_backlight_type() locks its function static init_mutex So in the first call sequence we have: a) init_mutex gets locked b) notifier-chain gets locked and in the second call sequence we have: 1) notifier-chain gets locked 2) init_mutex gets locked And we've a circular locking dependency. This specific locking dependency is fixable without using the big hammer otherwise known as a workqueue, but further analysis shows a similar problem with the backlight notifier chain lock vs register_count_mutex from drivers/acpi/acpi_video.c, and fixing that becomes problematic. So this commit simply fixes this with the big hammer, performance wise this is a non issue as we expect the work to get scheduled exactly zero or one times during normal system use. Fixes: 93a291dfaf9c (ACPI / video: Move backlight notifier to video_detect.c) Signed-off-by: Hans de Goede <hdegoede@redhat.com> Reported-and-tested-by: Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-08-13 16:53:37 +00:00
INIT_WORK(&backlight_notify_work,
acpi_video_backlight_notify_work);
backlight_nb.notifier_call = acpi_video_backlight_notify;
backlight_nb.priority = 0;
if (backlight_register_notifier(&backlight_nb) == 0)
backlight_notifier_registered = true;
init_done = true;
}
mutex_unlock(&init_mutex);
if (acpi_backlight_cmdline != acpi_backlight_undef)
return acpi_backlight_cmdline;
if (acpi_backlight_dmi != acpi_backlight_undef)
return acpi_backlight_dmi;
if (!(video_caps & ACPI_VIDEO_BACKLIGHT))
return acpi_backlight_vendor;
if (acpi_osi_is_win8() && backlight_device_get_by_type(BACKLIGHT_RAW))
return acpi_backlight_native;
return acpi_backlight_video;
}
EXPORT_SYMBOL(acpi_video_get_backlight_type);
/*
* Set the preferred backlight interface type based on DMI info.
* This function allows DMI blacklists to be implemented by external
* platform drivers instead of putting a big blacklist in video_detect.c
*/
void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
{
acpi_backlight_dmi = type;
/* Remove acpi-video backlight interface if it is no longer desired */
if (acpi_video_get_backlight_type() != acpi_backlight_video)
acpi_video_unregister_backlight();
}
EXPORT_SYMBOL(acpi_video_set_dmi_backlight_type);
void __exit acpi_video_detect_exit(void)
{
if (backlight_notifier_registered)
backlight_unregister_notifier(&backlight_nb);
}