how do I get xbacklight to work?

wchouser3 · 2015-12-08 08:44:49

I read the wiki, but it was a bit confusing because it was written for someone with an intel processor. What I need to do is add the appropriate info to the xorg config so that xbacklight can control the screen brightness of my hp laptop. Here is my lspci:

00:00.0 Host bridge: Advanced Micro Devices, Inc. [AMD] RS880 Host Bridge
00:01.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780/RS880 PCI to PCI bridge (int gfx)
00:05.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780/RS880 PCI to PCI bridge (PCIE port 1)
00:06.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780 PCI to PCI bridge (PCIE port 2)
00:11.0 SATA controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 SATA Controller [AHCI mode]
00:12.0 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
00:12.2 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB EHCI Controller
00:13.0 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
00:13.2 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB EHCI Controller
00:14.0 SMBus: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 SMBus Controller (rev 42)
00:14.2 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 Azalia (Intel HDA) (rev 40)
00:14.3 ISA bridge: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 LPC host controller (rev 40)
00:14.4 PCI bridge: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 PCI to PCI Bridge (rev 40)
00:14.5 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI2 Controller
00:16.0 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
00:16.2 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB EHCI Controller
00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor HyperTransport Configuration
00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor Address Map
00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor Miscellaneous Control
00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor Link Control
01:05.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RS880M [Mobility Radeon HD 4225/4250]
01:05.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] RS880 HDMI Audio [Radeon HD 4200 Series]
02:00.0 Network controller: Qualcomm Atheros AR9285 Wireless Network Adapter (PCI-Express) (rev 01)
03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 03)

without the correct xorg setting I get that "No outputs have backlight property."

can someone tell me exactly what to add when using the open-source Radeon driver?

Also, I added "acpi_backlight=vendor" to my kernel parameters. Without it, it was being controlled by ACPI, and Radeon. Should I, or Should I not have done that?

Raynman · 2015-12-08 15:37:06

That option in the xorg config is only for the intel driver. The radeon driver simply does not support the backlight properties for the RandR extension, so you're out of luck. You can probably use sysfs (/sys/class/backlight/... with or without kernel parameters) with the appropriate permissions.

Disclaimer: it's been a while since I looked into this and I may be unaware of recent developments, but at the time it seemed unlikely that radeon was ever going to support the backlight property.

Last edited by Raynman (2015-12-08 15:37:32)

wchouser3 · 2015-12-08 19:49:31

Raynman wrote:

That option in the xorg config is only for the intel driver. The radeon driver simply does not support the backlight properties for the RandR extension, so you're out of luck. You can probably use sysfs (/sys/class/backlight/... with or without kernel parameters) with the appropriate permissions.
Disclaimer: it's been a while since I looked into this and I may be unaware of recent developments, but at the time it seemed unlikely that radeon was ever going to support the backlight property.

ok...I appreciate your response. I've been using backlight-control from the AUR for years (though it had been orphaned the whole time) I guess I'll have to try something else, or adopt the backlight control package myself.

--edit: I just installed "Light" from the AUR, and it works beautifully

Last edited by wchouser3 (2015-12-08 20:18:38)

wchouser3 · 2015-12-09 06:30:10

Now, just to be clear: xbacklight doesn't work at all with Radeon GPU's. Is that correct? If that's true, I'm getting rid of it.

Arch Linux

#1 2015-12-08 08:44:49

how do I get xbacklight to work?

#2 2015-12-08 15:37:06

Re: how do I get xbacklight to work?

#3 2015-12-08 19:49:31

Re: how do I get xbacklight to work?

#4 2015-12-09 06:30:10

Re: how do I get xbacklight to work?

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