TW / Nvidia - where did /sys/class/backlight/acpi_video0/ go?
All, Fresh install of Tumbleweed is progressing. US Mirrors are still in total chaos. Throughput of 0Kbs - 120Kbs is all we get. Over an hour to download KDE3, Firefox and Thunderbird... But, we did get the network up - albeit with a nmtui connect hack. Bigger issue is the sysfs backlight control interface for my laptop display is just gone. On 15.4 I use: /sys/class/backlight/acpi_video0/brightness to control display brightness. With TW, I have the same Nvidia driver installed, but there is no /sys/class/backlight/acpi_video0 (in fact there is nothing in /sys/class/backlight) That means I can't set the laptop display brightness and it is BLINDING. It is currently set at 100%. Where did /sys/class/backlight/acpi_video0 go, and is there any way to get it back? -- David C. Rankin, J.D.,P.E.
Hello, In the Message; Subject : TW / Nvidia - where did /sys/class/backlight/acpi_video0/ go? Message-ID : <41d1cf06-59cf-4d1a-8b0a-d31c9f99b0d3@gmail.com> Date & Time: Sun, 7 Jul 2024 19:02:00 -0500 [DCR] == "David C. Rankin" <drankinatty@gmail.com> has written: [...] DCR> That means I can't set the laptop display brightness and it is BLINDING. It is currently set at 100%. DCR> Where did /sys/class/backlight/acpi_video0 go, and is there DCR> any way to get it back? How about this? 1. edit etc/default/grub as follows; add acpi_backlight=vendor to GRUB_CMDLINE_LINUX_DEFAULT 2. $ sudo grub2-mkconfig -o /boot/grub2/grub.cfg 3. reboot Best Regards. --- ┏━━┓彡 Masaru Nomiya mail-to: nomiya @ lake.dti.ne.jp ┃＼／彡 ┗━━┛ "Distinguish between what is meaningful to me and what is meaningless, and forget what is meaningless to me. This is where individuality comes into play. This is a function that computer cannot perform." -- Shigehiko Toyama (in Japanes) --
On 7/7/24 20:44, Masaru Nomiya wrote:
How about this?
1. edit etc/default/grub as follows;
add acpi_backlight=vendor to GRUB_CMDLINE_LINUX_DEFAULT
2. $ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
3. reboot
Thank you for your reply Masaru, But... no joy... It doesn't make any difference to what is present in /sys/class/backlight. It was still empty :( I think this actually has to be done as part of the driver build -- which if it is overlooked there, acpi_video0 won't be present. I think we need to check the new NVIDIA service that appeared on my TW install and pulled in the driver to see if it may not be missing the acpi_backlight=vendor (or similar) option. This option is not present in 15.4 and the acpi_video0 interface is provided. So TW is doing something different that causes it to fail to appear in /sys/class/backlight. Anything else you can think of? -- David C. Rankin, J.D.,P.E.
Hello, In the Message; Subject : Re: TW / Nvidia - where did /sys/class/backlight/acpi_video0/ go? Message-ID : <ad19736f-9738-41eb-b61c-00fc15db8fb1@gmail.com> Date & Time: Mon, 8 Jul 2024 03:33:59 -0500 [DCR] == "David C. Rankin" <drankinatty@gmail.com> has written: DCR> On 7/7/24 20:44, Masaru Nomiya wrote: MN> > How about this? MN> > 1. edit etc/default/grub as follows; MN> > add acpi_backlight=vendor to GRUB_CMDLINE_LINUX_DEFAULT MN> > 2. $ sudo grub2-mkconfig -o /boot/grub2/grub.cfg MN> > 3. reboot DCR> Thank you for your reply Masaru, DCR> But... no joy... It doesn't make any difference to what is present in DCR> /sys/class/backlight. It was still empty :( DCR> I think this actually has to be done as part of the driver DCR> build -- which if it is overlooked there, acpi_video0 won't be present. DCR> I think we need to check the new NVIDIA service that appeared DCR> on my TW install and pulled in the driver to see if it may not DCR> be missing the acpi_backlight=vendor (or similar) option. DCR> This option is not present in 15.4 and the acpi_video0 interface is DCR> provided. So TW is doing something different that causes it to DCR> fail to appear in DCR> /sys/class/backlight. DCR> Anything else you can think of? How about this? 1. acpi_backlight=native or 2. acpi_backlight=video Best Regards. --- ┏━━┓彡 Masaru Nomiya mail-to: nomiya @ lake.dti.ne.jp ┃＼／彡 ┗━━┛ Japan is now, Dangerously hot!
On 7/8/24 04:23, Masaru Nomiya wrote:
How about this?
1. acpi_backlight=native
or
2. acpi_backlight=video
I'll try but from all the other posts, that usually results in: native - acpi_video0 (present but doesn't provide backlight control) video - acpi_video0 (not present) vendor - acpi_video0 (not present) I'll report back with TW results, but suspect I won't find anything different. *** Second Post Reply ***
DCR> Anybody recall just what/where the fix was made to restore acpi_video0 for DCR> backlight control? Was it a kernel config or Nvidia module build file?
I hope this is not the case.
https://forums.developer.nvidia.com/t/backlight-brightness-very-low-when-usi... <snip>
I hope you are right, but if I recall from the 2016 issue, it was ultimately fixed in discussions between the openSUSE Nvidia contact and Nvidia - which points to a possible issue in their secret part. Though for the G04 driver -- it would have to be a regression in the common code that goes into their blob as this driver doesn't change any more and is considered legacy. -- David C. Rankin, J.D.,P.E.
On 7/8/24 4:23 AM, Masaru Nomiya wrote:
How about this?
1. acpi_backlight=native
or
2. acpi_backlight=video
We have a winner!!! No. 2 did in fact work, e.g.: 14:06 wizard:~> l /sys/class/backlight/ total 0 drwxr-xr-x 2 root root 0 Jul 8 14:07 . drwxr-xr-x 68 root root 0 Jul 8 14:06 .. lrwxrwxrwx 1 root root 0 Jul 8 14:06 acpi_video0 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0 14:07 wizard:~> bl Current Brightness: 7 (0-20) 14:07 wizard:~> cat /proc/cmdline BOOT_IMAGE=/boot/vmlinuz-6.9.7-1-default root=UUID=17f7b9ba-8760-4a74-bcc3-3f4ff0908233 splash=silent quiet security=apparmor mitigations=off nosimplefb=1 acpi_backlight=video 14:07 wizard:~> "native" and "vendor" produced no acpi_video0 in /sys/class/backlight, e.g. 13:59 wizard:~> l /sys/class/backlight total 0 drwxr-xr-x 2 root root 0 Jul 8 13:59 . drwxr-xr-x 68 root root 0 Jul 8 13:58 .. 13:59 wizard:~> cat /proc/cmdline BOOT_IMAGE=/boot/vmlinuz-6.9.7-1-default root=UUID=17f7b9ba-8760-4a74-bcc3-3f4ff0908233 splash=silent quiet security=apparmor mitigations=off nosimplefb=1 acpi_backlight=native 13:59 wizard:~> Thank you Masaru and thank goodness it wasn't something in the binary part of the driver. -- David C. Rankin, J.D.,P.E.
On 7/7/24 20:44, Masaru Nomiya wrote:
How about this?
1. edit etc/default/grub as follows;
add acpi_backlight=vendor to GRUB_CMDLINE_LINUX_DEFAULT
2. $ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
3. reboot
Masaru, Sorry for the 2nd reply, but I no longer get my own posts using gmail. The reason I say this requires either a driver or kernel module change on the openSUSE/Nvidia end is this has happened before, e.g. https://lists.opensuse.org/archives/list/users@lists.opensuse.org/thread/YVQ... I don't recall the specifics, but I do clearly recall it being a problem that had to be fixed on the openSUSE end. I also do believe your acpi_backlight=vendor is what was missing - but it wasn't a simple grub command line fix that was needed. Anybody recall just what/where the fix was made to restore acpi_video0 for backlight control? Was it a kernel config or Nvidia module build file? -- David C. Rankin, J.D.,P.E.
Hello, In the Message; Subject : Re: TW / Nvidia - where did /sys/class/backlight/acpi_video0/ go? Message-ID : <25f08046-0033-4351-89ea-cfd134a7ce0d@gmail.com> Date & Time: Mon, 8 Jul 2024 04:23:17 -0500 [DCR] == "David C. Rankin" <drankinatty@gmail.com> has written: [...] DCR> Masaru, DCR> Sorry for the 2nd reply, but I no longer get my own posts using gmail. DCR> The reason I say this requires either a driver or kernel DCR> module change on the openSUSE/Nvidia end is this has happened DCR> before, e.g. DCR> https://lists.opensuse.org/archives/list/users@lists.opensuse.org/thread/YVQ... DCR> I don't recall the specifics, but I do clearly recall it being DCR> a problem that had to be fixed on the openSUSE end. I also do believe your DCR> acpi_backlight=vendor is what was missing - but it wasn't a DCR> simple grub command line fix that was needed. DCR> Anybody recall just what/where the fix was made to restore acpi_video0 for DCR> backlight control? Was it a kernel config or Nvidia module build file? I hope this is not the case. https://forums.developer.nvidia.com/t/backlight-brightness-very-low-when-usi... Checking the nouveau driver, the values are read directly from the panel over the eDP connector. So I guess no bios update or acpi fiddling can fix it. Unfortunately, the nvidia driver also makes a secret out of this, handling backlight control in the blob. Even the nvidia-open driver handles this in the firmware blob. So only method that comes to my mind is patching the nvidia driver to not register the backlight device and instead try to enable an acpi handler, e.g. with kernel parameter acpi_backlight=video Best Regards & Good Night. --- ┏━━┓彡 Masaru Nomiya mail-to: nomiya @ lake.dti.ne.jp ┃＼／彡 ┗━━┛ "To hire for skills, firms will need to implement robust and intentional changes in their hiring practices ― and change is hard." -- Employers don’t practice what they preach on skills-based hiring --
participants (2)
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David C. Rankin -
Masaru Nomiya