Problem with LCD brightness buttons - Revision history

WilliamPoetra: /* Change permissions on the brightness file */

2019-04-07T12:07:57Z

‎Change permissions on the brightness file

WilliamPoetra: /* Modify the parameter for video.ko at runtime */

2019-04-07T11:38:28Z

‎Modify the parameter for video.ko at runtime

WilliamPoetra: /* Workaround */

2019-04-07T11:36:54Z

‎Workaround

WilliamPoetra: /* Workaround */

2019-04-06T09:22:31Z

‎Workaround

WilliamPoetra: /* Workaround */

2019-04-06T09:21:46Z

‎Workaround

WilliamPoetra: /* Workaround */

2019-04-05T19:26:36Z

‎Workaround

Azerttyu at 18:06, 17 January 2016

2016-01-17T18:06:37Z

WilliamPoetra: /* Affected Models */

2015-11-02T01:59:54Z

‎Affected Models

WilliamPoetra at 16:51, 1 November 2015

2015-11-01T16:51:09Z

Ekilachkoff: /* Workaround */ disabling brightness control in video.ko

2013-04-07T08:45:51Z

‎Workaround: disabling brightness control in video.ko

@@ Line 60: / Line 60: @@
 Then chmod the brightness file so the power manager can't write to it.
-  # chmod 444 /sys/class/backlight/intel_backlight/type
+  # chmod 444 /sys/class/backlight/intel_backlight/brightness
 Incidentally, this also fixes the brightness reset upon plug or unplug of the power cable.

@@ Line 42: / Line 42: @@
 Another alternative, one can issue this command or put it in <code>/etc/rc.local</code>:
-  echo N > /sys/module/video/parameters/brightness_switch_enabled
+  # echo N | tee /sys/module/video/parameters/brightness_switch_enabled
 === Update Grub loading ===

@@ Line 21: / Line 21: @@
 There are a number of workarounds for this problem. After applying the workarounds, you will be able to use brightness up {{key|Fn}}{{key|Home}} and brightness down {{key|Fn}}{{key|End}} to increase and decrease the LCD brightness as normal.
-'''Note for T420s users:''' Using the workarounds listed below in Linux Mint 19.1 MATE introduces a weird bug, whereby the brightness is reset every time the power cord is plugged or unplugged. It also disables the brightness keys when we are at the login screen. This does not occur on Linux Mint 19.1 Cinnamon and Ubuntu 18.04.1 Desktop. In fact, for those distros we do not need to apply any of the workarounds below at all.
+'''Note for T420s users:''' Using the workarounds listed below (except the chmod workaround) in Linux Mint 19.1 MATE introduces a weird bug, whereby the brightness is reset every time the power cord is plugged or unplugged. It also disables the brightness keys when we are at the login screen. This does not occur on Linux Mint 19.1 Cinnamon and Ubuntu 18.04.1 Desktop. In fact, for those distros we do not need to apply any of the workarounds below at all.
 === Don't load the ACPI video module ===
@@ Line 28: / Line 28: @@
 For Fedora Core 6 users, issue the following command and reboot:
-{{cmdroot|rename ko ko.old /lib/modules/$(uname -r)/kernel/drivers/acpi/video.ko }}
+ # rename ko ko.old /lib/modules/$(uname -r)/kernel/drivers/acpi/video.ko
 === Specify a parameter for video.ko ===
@@ Line 36: / Line 36: @@
 There is a number of ways to introduce this parameter, one of them is creating a configuration file for modprobe. The next command works on Debian 6 (and maybe some other systems):
-{{cmdroot|1=echo options video brightness_switch_enabled=0 {{!}} tee /etc/modprobe.d/video-br.conf}}
+ # echo options video brightness_switch_enabled=0 | tee /etc/modprobe.d/video-br.conf
 === Modify the parameter for video.ko at runtime ===
@@ Line 50: / Line 50: @@
 Add to GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub
    video.use_native_backlight=0
 == Remaining issues ==

@@ Line 21: / Line 21: @@
 There are a number of workarounds for this problem. After applying the workarounds, you will be able to use brightness up {{key|Fn}}{{key|Home}} and brightness down {{key|Fn}}{{key|End}} to increase and decrease the LCD brightness as normal.
-'''Note for T420s users:''' Using the workarounds listed below in Linux Mint 19.1 MATE introduces a weird bug, whereby the brightness is reset every time the power cord is plugged or unplugged. It also disables the brightness keys when we are at the login screen. This does not occur on Linux Mint 19.1 Cinnamon and Ubuntu 18.04.1 Desktop.
+'''Note for T420s users:''' Using the workarounds listed below in Linux Mint 19.1 MATE introduces a weird bug, whereby the brightness is reset every time the power cord is plugged or unplugged. It also disables the brightness keys when we are at the login screen. This does not occur on Linux Mint 19.1 Cinnamon and Ubuntu 18.04.1 Desktop. In fact, for those distros we do not need to apply any of the workarounds below at all.
 === Don't load the ACPI video module ===

@@ Line 21: / Line 21: @@
 There are a number of workarounds for this problem. After applying the workarounds, you will be able to use brightness up {{key|Fn}}{{key|Home}} and brightness down {{key|Fn}}{{key|End}} to increase and decrease the LCD brightness as normal.
-'''Note for T420s users:''' Using the workarounds listed below in Linux Mint 19.1 introduces a weird bug, whereby the brightness is reset every time the power cord is plugged or unplugged. It also disables the brightness keys when we are at the login screen.
+'''Note for T420s users:''' Using the workarounds listed below in Linux Mint 19.1 MATE introduces a weird bug, whereby the brightness is reset every time the power cord is plugged or unplugged. It also disables the brightness keys when we are at the login screen. This does not occur on Linux Mint 19.1 Cinnamon and Ubuntu 18.04.1 Desktop.
 === Don't load the ACPI video module ===

← Older revision		Revision as of 18:06, 17 January 2016
Line 41:		Line 41:

	echo N > /sys/module/video/parameters/brightness_switch_enabled		echo N > /sys/module/video/parameters/brightness_switch_enabled
		+
		+	=== Update Grub loading ===
		+
		+	From https://bbs.archlinux.org/viewtopic.php?id=184949&p=2
		+
		+	Add to GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub
		+	video.use_native_backlight=0
		+

	== Remaining issues ==		== Remaining issues ==

@@ Line 3: / Line 3: @@
 * {{T60}}, {{T60p}} with BIOS 2.x
 * {{R60}} with BIOS 2.x
 * {{T420s}}
 * Probably all newer ThinkPads since the Lenovo acquisition

@@ Line 3: / Line 3: @@
 * {{T60}}, {{T60p}} with BIOS 2.x
 * {{R60}} with BIOS 2.x
 == Problem description ==
-A recent change in one of the newer Lenovo bios updates changed the brightness up key to also provide a ACPI video brighness up event.  This made ThinkPad users suffer from a bug in the Linux kernel handling of ACPI video events.
+A recent change in one of the newer Lenovo BIOS updates changed the behavior of the brightness up/down keys, so that they also provide ACPI video brighness up/down events. This made ThinkPad users suffer from a bug in the Linux kernel handling of ACPI video events.
 The Linux kernel handling for the ACPI video event brighness up is not implemented by the ACPI video module before Linux 2.6.20-rc?, which results in the brightness up key not working, even if the event is handled correctly.
@@ Line 13: / Line 17: @@
 == Workaround ==
 Don't load the ACPI video module, or don't compile in the ACPI_VIDEO option on Linux kernels that have not been patched to fix this issue.  The ThinkPad BIOS will do the right thing.
@@ Line 19: / Line 27: @@
 {{cmdroot|rename ko ko.old /lib/modules/$(uname -r)/kernel/drivers/acpi/video.ko }}
-After this, you will be able to use {{key|Fn}}{{key|Home}} and {{key|Fn}}{{key|End}} to increase and decrease the LCD brightness respectively.
+=== Specify a parameter for video.ko ===
-As an alternative, one might also specify brightness_switch_enabled=0 in video.ko parameters. With this parameter, all functionality of video.ko remains but without the brightness control and reaction to brightness ACPI events.
+As an alternative, one might also specify <code>brightness_switch_enabled=0</code> in <code>video.ko</code> parameters. With this parameter, all functionality of <code>video.ko</code> remains but without the brightness control and reaction to brightness ACPI events.
 There is a number of ways to introduce this parameter, one of them is creating a configuration file for modprobe. The next command works on Debian 6 (and maybe some other systems):
 {{cmdroot|1=echo options video brightness_switch_enabled=0 {{!}} tee /etc/modprobe.d/video-br.conf}}
 == Remaining issues ==
@@ Line 33: / Line 47: @@
 The fixed ACPI video module will use the ACPI DSDT to increase video brighness, but the new BIOS DSDTs apparently do not keep the CMOS NVRAM completely up-to-date, so [[tpb]] and other utilities that provide on-screen-display do not get to know there was a brightness up event.
-This can be argued to be a deficiency of these tools, however.  The foolproof, safe way to know the current ThinkPad display brightness in Linux is to ask [[ibm-acpi]]. Note that ibm-acpi support for this functionality is new, which explains why the current tools don't use it.
+This can be argued to be a deficiency of these tools, however. The foolproof, safe way to know the current ThinkPad display brightness in Linux is to ask [[ibm-acpi]]. Note that ibm-acpi support for this functionality is new, which explains why the current tools don't use it.
 Due to the fact that when nothing handles the ACPI video brighness up event, the BIOS does the right thing, it is unclear at this time exactly where the blame for this remaining issue should lie.

← Older revision		Revision as of 08:45, 7 April 2013
Line 20:		Line 20:

	After this, you will be able to use {{key\|Fn}}{{key\|Home}} and {{key\|Fn}}{{key\|End}} to increase and decrease the LCD brightness respectively.		After this, you will be able to use {{key\|Fn}}{{key\|Home}} and {{key\|Fn}}{{key\|End}} to increase and decrease the LCD brightness respectively.
		+
		+	As an alternative, one might also specify brightness_switch_enabled=0 in video.ko parameters. With this parameter, all functionality of video.ko remains but without the brightness control and reaction to brightness ACPI events.
		+
		+	There is a number of ways to introduce this parameter, one of them is creating a configuration file for modprobe. The next command works on Debian 6 (and maybe some other systems):
		+
		+	{{cmdroot\|1=echo options video brightness_switch_enabled=0 {{!}} tee /etc/modprobe.d/video-br.conf}}

	== Remaining issues ==		== Remaining issues ==