backlight

I'm running linux 2.6.28-rc6-00007-ged31348 on my Thinkpad T61, with Intel GM965. Under X, brightness keys work fine most of the time, but in some case it fails (for example after a dpms force off, but not always). Switching to console and back to X fix the problem for a time.

Another weird stuff is that, in single user, I have no way to control the backlight. Using brightness key doesn't work,
and /sys/class/backlight/acpi_video0 doesn't do anything.

From d5b5f1bf810dcc87d5d6adb6efbaee8bff6d796c Mon Sep 17 00:00:00 2001

Quoted 4 lines · Yves-Alexis Perez

I'm running linux 2.6.28-rc6-00007-ged31348 on my Thinkpad T61, with Intel GM965. Under X, brightness keys work fine most of the time, but in some case it fails (for example after a dpms force off, but not always). Switching to console and back to X fix the problem for a time.

How to you invoke DPMS?

I'm running the latest 2.6.28 on top of FC9, and I find that if I use the hot keys to dim the screen all the way, and then I'm idle for a period, the screen pretends to go black. (X foolishly paits the pixels black, but keeps the backlight on) Then when I touch the mouse to wake it up, my screen unlock prompt is at full brightness, and so is my screen when I unlock. So it seems that X forgot that I set the brightness. (though clicking the brightness hotkey shows the widget still
thinks I'm at minimum brightness, so that part remembered...)

Now the backlight is totally screwed up.
I use the hotkeys to get to minimum brightness, but something thinks I'm still at maximum brightness, because after some idle time, the screen all by itself goes bright.

Quoted 3 lines

Another weird stuff is that, in single user, I have no way to control the backlight. Using brightness key doesn't work,
and /sys/class/backlight/acpi_video0 doesn't do anything.

There are actually two text consoles -- CTRL-ALT-F1 while X is running and single-user mode.

The hot keys have never worked for either of these modes.

I would hope that X (i915) should be able to handle brightness in CTRL-ALT-F1 mode the same way that it does in GUI mode, but that doesn't seem to be working.

Then there is single-user-mode, where X never ran
and the i915 may not even be loaded...

We used to have /sys/class/backlight and /proc/acpi/video available and they used to work in single-user mode (as well as in CTRL-ALT-F1) mode. This was due to there being two video devices. Unfortunately, we deleted the one what works in this scenario.

Try this patch, which brings it back.

thanks,
-Len

From d5b5f1bf810dcc87d5d6adb6efbaee8bff6d796c Mon Sep 17 00:00:00 2001
From: Len Brown <[email protected]>
Date: Fri, 28 Nov 2008 14:02:52 -0500
Subject: [PATCH] Partial revert "ACPI: video: Ignore devices that aren't present in hardware" Organization: Intel Open Source Technology Center

22c13f9d8179f4c9caecfcb60a95214562b9addc
"ACPI: video: Ignore devices that aren't present in hardware"

caused the 2nd /proc/acpi/video
and /sys/firmware/backlight device to go away,
making software brightness control unavailable
in single-user-mode and X text-console-mode,
on a Thinkpad T61.

Signed-off-by Len Brown <[email protected]>

---
 drivers/acpi/video.c |    6 ------
 1 files changed, 0 insertions(+), 6 deletions(-)

drivers/acpi/video.c +0 -0

index baa4419..f930413 100644
@@ -845,16 +845,10 @@ static void acpi_video_bus_find_cap(struct

acpi_video_bus *video) static int acpi_video_bus_check(struct acpi_video_bus *video)
{

drivers/acpi/video.c +0 -6

 	acpi_status status = -ENOENT;
-	struct device *dev;
 
 	if (!video)
 		return -EINVAL;
 
-	dev = acpi_get_physical_pci_device(video->device->handle);
-	if (!dev)
-		return -ENODEV;
-	put_device(dev);
-
 	/* Since there is no HID, CID and so on for VGA driver, we have
 	 * to check well known required nodes.
 	 */

Quoted 4 lines · Yves-Alexis Perez

I'm running linux 2.6.28-rc6-00007-ged31348 on my Thinkpad T61, with Intel GM965. Under X, brightness keys work fine most of the time, but in some case it fails (for example after a dpms force off, but not always). Switching to console and back to X fix the problem for a time.

How to you invoke DPMS?

I'm running the latest 2.6.28 on top of FC9, and I find that if I use the hot keys to dim the screen all the way, and then I'm idle for a period, the screen pretends to go black. (X foolishly paits the pixels black, but keeps the backlight on) Then when I touch the mouse to wake it up, my screen unlock prompt is at full brightness, and so is my screen when I unlock. So it seems that X forgot that I set the brightness. (though clicking the brightness hotkey shows the widget still
thinks I'm at minimum brightness, so that part remembered...)

Now the backlight is totally screwed up.
I use the hotkeys to get to minimum brightness, but something thinks I'm still at maximum brightness, because after some idle time, the screen all by itself goes bright.

Quoted 4 lines

Another weird stuff is that, in single user, I have no way to control the backlight. Using brightness key doesn't work,
and /sys/class/backlight/acpi_video0 doesn't do anything.

There are actually two text consoles -- CTRL-ALT-F1 while X is running and single-user mode.

The hot keys have never worked for either of these modes.

I would hope that X (i915) should be able to handle brightness in CTRL-ALT-F1 mode the same way that it does in GUI mode, but that doesn't seem to be working.

Then there is single-user-mode, where X never ran
and the i915 may not even be loaded...

We used to have /sys/class/backlight and /proc/acpi/video available and they used to work in single-user mode (as well as in CTRL-ALT-F1) mode. This was due to there being two video devices. Unfortunately, we deleted the one what works in this scenario.

Try this patch, which brings it back.

Quoted 8 lines · Len Brown

Quoted 4 lines · Yves-Alexis Perez

I'm running linux 2.6.28-rc6-00007-ged31348 on my Thinkpad T61, with Intel GM965. Under X, brightness keys work fine most of the time, but in some case it fails (for example after a dpms force off, but not always). Switching to console and back to X fix the problem for a time.

How to you invoke DPMS?

xorg.conf:
Section "ServerFlags"

  Option  "StandbyTime" "0"
  Option  "SuspendTime" "0"
  Option  "OffTime"   "5"

EndSection

Quoted 11 lines

I'm running the latest 2.6.28 on top of FC9, and I find that if I use the hot keys to dim the screen all the way, and then I'm idle for a period, the screen pretends to go black. (X foolishly paits the pixels black, but keeps the backlight on) Then when I touch the mouse to wake it up, my screen unlock prompt is at full brightness, and so is my screen when I unlock. So it seems that X forgot that I set the brightness. (though clicking the brightness hotkey shows the widget still
thinks I'm at minimum brightness, so that part remembered...)

Quoted 5 lines

Now the backlight is totally screwed up.
I use the hotkeys to get to minimum brightness, but something thinks I'm still at maximum brightness, because after some idle time, the screen all by itself goes bright.

Well I think that gnome-power-manager might be in your way, not sure.

Quoted 8 lines

Quoted 4 lines

Another weird stuff is that, in single user, I have no way to control the backlight. Using brightness key doesn't work,
and /sys/class/backlight/acpi_video0 doesn't do anything.

There are actually two text consoles -- CTRL-ALT-F1 while X is running and single-user mode.

Quoted 1 line

The hot keys have never worked for either of these modes.

Yes I know, that's why I'm asking here. They are not supposed to work atm because OpRegion needs X support. What I was asking is if there was something in cooking for that. But what puzzles me is that even the /sys/class/backlight/acpi_video0 doesn't work.

Quoted 8 lines

I would hope that X (i915) should be able to handle brightness in CTRL-ALT-F1 mode the same way that it does in GUI mode, but that doesn't seem to be working.

Then there is single-user-mode, where X never ran
and the i915 may not even be loaded...

Quoted 7 lines

We used to have /sys/class/backlight and /proc/acpi/video available and they used to work in single-user mode (as well as in CTRL-ALT-F1) mode. This was due to there being two video devices. Unfortunately, we deleted the one what works in this scenario.

Try this patch, which brings it back.

No, I don't want to revert those patches, they are there for a reason. But yeah there is some console support missing, which may be working on.

IMO, after loading i915 driver, the ACPI backlight I/F can work again, right?

If this is true, why not always loading i915 both in X and console mode? the kernel mode setting should not only work for X mode.

Quoted 3 lines

IMO, after loading i915 driver, the ACPI backlight I/F can work again, right?

No.
hotkeys have never worked in console mode,

but in 2.6.27, echo into /proc and /sys did work in console mode and in 2.6.28 they do not. So this is a regression.

Quoted 2 lines

If this is true, why not always loading i915 both in X and console mode? the kernel mode setting should not only work for X mode.

I agree that the i915 driver should handle brightness, no matter if we are in GUI mode or console mode. Unfortunately, today it doesn't seem to do anything in console mode.

That is why I pointed out that the regression here was when we deleted the /proc and /sys nodes that actualy work from console mode...

On a brightner note, I'm pleased to report that after upgrading my T61 to FC10 from FC9, the brightness suddenly became consistent across screen saver events. ie. the brightness I set via hotkey before the screen saver event was restored after the screen comes back from screen blank.

However, testing FC10 with the latest upstream kernel, including the i915 changes that appeared today... it seems that GUI mode forgets the brighness when I switch to console mode. Eg. If I use /sys or hotkeys in GUI mode to reduce brightness to 0, it stays dim when I switch to console mode, but switches back to max brightness when
I switch back to GUI mode.

Quoted 9 lines

However, testing FC10 with the latest upstream kernel, including the i915 changes that appeared today... it seems that GUI mode forgets the brighness when I switch to console mode. Eg. If I use /sys or hotkeys in GUI mode to reduce brightness to 0, it stays dim when I switch to console mode, but switches back to max brightness when
I switch back to GUI mode.

hah, that's a done by X.
ZhenYu pointed out that the graphics driver will set the backlight to maximum if it is 0 when switching to GUI.
what if reducing the brightness to a lower but not 0 level? it should switch back to the original value, right?
cc ZhenYU. :)

Quoted 8 lines

Quoted 8 lines

However, testing FC10 with the latest upstream kernel, including the i915 changes that appeared today... it seems that GUI mode forgets the brighness when I switch to console mode. Eg. If I use /sys or hotkeys in GUI mode to reduce brightness to 0, it stays dim when I switch to console mode, but switches back to max brightness when
I switch back to GUI mode.

Quoted 6 lines

hah, that's a done by X.
ZhenYu pointed out that the graphics driver will set the backlight to maximum if it is 0 when switching to GUI.
what if reducing the brightness to a lower but not 0 level? it should switch back to the original value, right?
cc ZhenYU. :)

This depends on the backlight control method used by Xorg video driver. We have this comment in the driver from Jesse I think,

/*
* If we're going from off->on we may need to turn on the backlight.
* We should use the saved value whenever possible, but on some
* machines 0 is a valid backlight value (due to an external backlight
* controller for example), so on them, when turning LVDS back on,
* they'll always re-maximize the brightness.
*/
if (!(INREG(PP_CONTROL) & POWER_TARGET_ON) &&

	dev_priv->backlight_duty_cycle == 0)
	dev_priv->backlight_duty_cycle = dev_priv->backlight_max;

It looks if we're using kernel backlight method, '0' should be a human sensible dim level instead of meaningless near-to-black level, right?

So how about this patch against current xf86-video-intel?

---

src/i830_lvds.c +0 -0

index 239bc89..1799eab 100644

Quoted 9 lines · Zhang Rui

Quoted 8 lines

However, testing FC10 with the latest upstream kernel, including the i915 changes that appeared today... it seems that GUI mode forgets the brighness when I switch to console mode. Eg. If I use /sys or hotkeys in GUI mode to reduce brightness to 0, it stays dim when I switch to console mode, but switches back to max brightness when
I switch back to GUI mode.

Quoted 6 lines

hah, that's a done by X.
ZhenYu pointed out that the graphics driver will set the backlight to maximum if it is 0 when switching to GUI.
what if reducing the brightness to a lower but not 0 level? it should switch back to the original value, right?
cc ZhenYU. :)

This depends on the backlight control method used by Xorg video driver. We have this comment in the driver from Jesse I think,

/*
* If we're going from off->on we may need to turn on the backlight.
* We should use the saved value whenever possible, but on some
* machines 0 is a valid backlight value (due to an external backlight
* controller for example), so on them, when turning LVDS back on,
* they'll always re-maximize the brightness.
*/
if (!(INREG(PP_CONTROL) & POWER_TARGET_ON) &&

	dev_priv->backlight_duty_cycle == 0)
	dev_priv->backlight_duty_cycle = dev_priv->backlight_max;

It looks if we're using kernel backlight method, '0' should be a human sensible dim level instead of meaningless near-to-black level, right?

So how about this patch against current xf86-video-intel?

---

src/i830_lvds.c +2 -2

index 239bc89..1799eab 100644
@@ -400,7 +400,8 @@ i830SetLVDSPanelPower(xf86OutputPtr output, Bool on)
 	 * they'll always re-maximize the brightness.
 	 */
 	if (!(INREG(PP_CONTROL) & POWER_TARGET_ON) &&
-	    dev_priv->backlight_duty_cycle == 0)
+	    dev_priv->backlight_duty_cycle == 0 &&
+	    pI830->backlight_control_method < BCM_KERNEL)
 	    dev_priv->backlight_duty_cycle = dev_priv->backlight_max;
 
 	OUTREG(PP_CONTROL, INREG(PP_CONTROL) | POWER_TARGET_ON);
---

p.s Len, if for intel graphics specific issue, we have another [email protected] for such discuss. Thanks.

Hi,

I'm running linux 2.6.28-rc6-00007-ged31348 on my Thinkpad T61, with Intel GM965. Under X, brightness keys work fine most of the time, but in some case it fails (for example after a dpms force off, but not always). Switching to console and back to X fix the problem for a time.

Another weird stuff is that, in single user, I have no way to control the backlight. Using brightness key doesn't work,
and /sys/class/backlight/acpi_video0 doesn't do anything.

I know there was a lot of enhancements with OpRegion stuff for 2.6.27 and 2.6.28, and it's maybe not finished, but are those problems known?

Cheers, and many thanks for the good work :)

Quoted 6 lines · Yves-Alexis Perez

Hi,

I'm running linux 2.6.28-rc6-00007-ged31348 on my Thinkpad T61, with Intel GM965. Under X, brightness keys work fine most of the time, but in some case it fails (for example after a dpms force off, but not always). Switching to console and back to X fix the problem for a time.

Will you please confirm whether the issue still exists if DPMS is not used?

Quoted 3 lines

Another weird stuff is that, in single user, I have no way to control the backlight. Using brightness key doesn't work,
and /sys/class/backlight/acpi_video0 doesn't do anything.

Can you confirm whether the i915 driver is loaded in single user mode? If not, please load it and see whether the interface
of /sys/class/backlight/* can work.

in single user mode, i915 is not loaded,
/sys/class/backlight/acpi_video0 does NOT work

modprobe of i915 does not change this.

On Sun, Nov 30, 2008 at 10:28:30PM -0500, Len Brown wrote:

(Cc:ing Jesse)

Quoted 4 lines

in single user mode, i915 is not loaded,
/sys/class/backlight/acpi_video0 does NOT work

modprobe of i915 does not change this.

Jesse, are IRQs being delivered to the drm code when X isn't the foreground VT? If not, this would seem to need fixing.

Quoted 2 lines · Matthew Garrett

Jesse, are IRQs being delivered to the drm code when X isn't the foreground VT? If not, this would seem to need fixing.

The X driver calls into the DRM to disable IRQs when it releases the VT, but we could make that just affect vblank interrupts if needed (yay more i915_irq.c changes).

Quoted 6 lines · Yves-Alexis Perez

Hi,

I'm running linux 2.6.28-rc6-00007-ged31348 on my Thinkpad T61, with Intel GM965. Under X, brightness keys work fine most of the time, but in some case it fails (for example after a dpms force off, but not always). Switching to console and back to X fix the problem for a time.

Will you please confirm whether the issue still exists if DPMS is not used?

Quoted 4 lines

Another weird stuff is that, in single user, I have no way to control the backlight. Using brightness key doesn't work,
and /sys/class/backlight/acpi_video0 doesn't do anything.

Can you confirm whether the i915 driver is loaded in single user mode?

If not, please load it and see whether the interface of /sys/class/backlight/* can work.