Screen is very dark and brightness cannot be adjusted

[Pierre Equoy]

Device: Dell Precision 7530
In the BIOS, the Switchable Graphics option is deactived, which means only the nVidia GPU is used.

When booting 19.04 beta live USB, the screen becomes very dark and brightness cannot be adjusted. (The same issue happens with 18.04.2)

There is only a "nv_backlight" in /sys/class/backlight/ (i.e. no intel_backlight):

$ ll /sys/class/backlight/
total 0
drwxr-xr-x 2 root root 0 Mar 27 09:36 ./
drwxr-xr-x 74 root root 0 Mar 27 09:28 ../
lrwxrwxrwx 1 root root 0 Mar 27 09:28 nv_backlight -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card0/card0-eDP-1/nv_backlight/

Trying to manually change brightness doesn't do anything:

$ sudo su
root@ubuntu:/home/ubuntu# cd /sys/class/backlight/nv_backlight
root@ubuntu:/sys/class/backlight/nv_backlight# ll
total 0
drwxr-xr-x 3 root root 0 Mar 27 09:28 ./
drwxr-xr-x 4 root root 0 Mar 27 09:28 ../
-r--r--r-- 1 root root 4096 Mar 27 09:37 actual_brightness
-rw-r--r-- 1 root root 4096 Mar 27 09:37 bl_power
-rw-r--r-- 1 root root 4096 Mar 27 09:28 brightness
lrwxrwxrwx 1 root root 0 Mar 27 09:37 device -> ../../card0-eDP-1/
-r--r--r-- 1 root root 4096 Mar 27 09:28 max_brightness
drwxr-xr-x 2 root root 0 Mar 27 09:28 power/
lrwxrwxrwx 1 root root 0 Mar 27 09:28 subsystem -> ../../../../../../../../class/backlight/
-r--r--r-- 1 root root 4096 Mar 27 09:28 type
-rw-r--r-- 1 root root 4096 Mar 27 09:28 uevent
root@ubuntu:/sys/class/backlight/nv_backlight# cat actual_brightness
100
root@ubuntu:/sys/class/backlight/nv_backlight# cat brightness
100
root@ubuntu:/sys/class/backlight/nv_backlight# cat max_brightness
100
root@ubuntu:/sys/class/backlight/nv_backlight# echo 50 > brightness
root@ubuntu:/sys/class/backlight/nv_backlight# cat brightness
50

Although the value is changed, the screen brightness doesn't change.

in dmesg, I can see the following:

[ 0.241878] ACPI: Added _OSI(Module Device)
[ 0.241878] ACPI: Added _OSI(Processor Device)
[ 0.241878] ACPI: Added _OSI(3.0 _SCP Extensions)
[ 0.241878] ACPI: Added _OSI(Processor Aggregator Device)
[ 0.241878] ACPI: Added _OSI(Linux-Dell-Video)
[ 0.241878] ACPI: Added _OSI(Linux-Lenovo-NV-HDMI-Audio)
[ 0.241878] ACPI: Added _OSI(Linux-HPI-Hybrid-Graphics)
[ 0.286326] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS01._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.286332] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.286334] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.286336] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS01._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.286339] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.286340] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.287096] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS02._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.287099] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.287101] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.287102] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS02._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.287105] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.287106] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.287858] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS03._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.287861] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.287863] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.287864] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS03._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.287867] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.287869] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.288614] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS04._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.288617] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.288619] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.288620] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS04._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.288623] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.288625] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.289376] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS05._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.289379] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.289381] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.289382] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS05._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.289385] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.289386] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.290131] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS06._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.290134] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.290136] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.290137] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS06._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.290140] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.290142] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.290892] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS07._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.290895] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.290897] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.290898] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS07._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.290900] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.290902] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.291646] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS08._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.291649] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.291651] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.291652] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS08._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.291654] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.291656] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.292401] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS09._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.292404] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.292406] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.292407] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS09._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.292410] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.292411] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.293113] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS10._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.293117] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.293119] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.293120] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS10._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.293122] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.293124] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.293871] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS11._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.293874] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.293876] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.293877] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS11._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.293880] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.293882] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.294528] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS12._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.294531] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.294533] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.294534] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS12._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.294537] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.294539] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.295286] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS13._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.295289] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.295291] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.295292] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS13._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.295295] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.295297] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296046] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS14._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296049] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296051] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296052] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS14._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296055] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296057] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296772] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.USR1._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296776] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296777] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296778] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.USR1._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296781] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296783] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296785] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.USR2._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296788] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296790] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296791] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.USR2._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296793] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296795] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296821] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS01._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296824] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296826] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296827] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS01._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296830] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296831] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296855] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS02._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296858] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296860] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296861] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS02._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296864] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296866] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296889] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS03._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296892] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296894] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296895] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS03._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296898] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296900] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296923] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS04._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296926] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296928] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296929] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS04._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296932] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296934] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296957] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS05._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296960] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296962] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296963] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS05._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296966] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296968] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296991] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS06._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.296994] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.296996] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.296997] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS06._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.297000] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.297002] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.297025] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS07._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.297028] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.297030] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.297031] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS07._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.297034] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.297036] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.297060] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS08._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.297063] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.297064] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.297065] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS08._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.297068] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.297070] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.297094] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS09._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.297097] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.297098] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.297099] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS09._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.297102] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.297104] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.297128] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS10._UPC], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.297131] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.297133] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.297134] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.SS10._PLD], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.297136] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.297138] ACPI: Skipping parse of AML opcode: Method (0x0014)
[ 0.297140] ACPI BIOS Error (bug): Failure creating [\_SB.PCI0.XHC.RHUB.HS11.CAMB], AE_ALREADY_EXISTS (20181213/dswload2-324)
[ 0.297143] ACPI Error: AE_ALREADY_EXISTS, During name lookup/catalog (20181213/psobject-221)
[ 0.297145] ACPI: Skipping parse of AML opcode: Device (0x5B82)
[ 0.301048] ACPI: 13 ACPI AML tables successfully acquired and loaded
[ 0.312924] ACPI: [Firmware Bug]: BIOS _OSI(Linux) query ignored

ProblemType: Bug
DistroRelease: Ubuntu 19.04
Package: xorg 1:7.7+19ubuntu12
ProcVersionSignature: Ubuntu 5.0.0-7.8-generic 5.0.0
Uname: Linux 5.0.0-7-generic x86_64
ApportVersion: 2.20.10-0ubuntu23
Architecture: amd64
BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
CasperVersion: 1.402
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Wed Mar 27 09:29:56 2019
DistUpgraded: Fresh install
DistroCodename: disco
DistroVariant: ubuntu
ExtraDebuggingInterest: No
GraphicsCard:
 NVIDIA Corporation GP107GLM [Quadro P1000 Mobile] [10de:1cbb] (rev a1) (prog-if 00 [VGA controller])
   Subsystem: Dell GP107GLM [Quadro P1000 Mobile] [1028:1889]
LiveMediaBuild: Ubuntu 19.04 "Disco Dingo" - Alpha amd64 (20190326.2)
MachineType: Dell Inc. Precision 7530
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/username.seed boot=casper quiet splash ---
SourcePackage: xorg
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/10/2018
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.4.2
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.4.2:bd09/10/2018:svnDellInc.:pnPrecision7530:pvr:rvnDellInc.:rn:rvr:cvnDellInc.:ct10:cvr:
dmi.product.family: Precision
dmi.product.name: Precision 7530
dmi.product.sku: 0889
dmi.sys.vendor: Dell Inc.
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.97-1
version.libgl1-mesa-dri: libgl1-mesa-dri 19.0.0-1ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.20.4-1ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.0.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20180925-2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.16-1

[Pierre Equoy (pieq)]

I tried the same while blacklisting nouveau driver in grub:

$ cat /proc/cmdline
BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash modprobe.blacklist=nouveau ---

This time, I have "acpi_video0" in /sys/class/backlight, but the result is the same. The screen is very dark.

/sys/class/backlight/acpi_video0/brightness is 100 by default. I can modify this value with

$ sudo su
# echo 60 > /sys/class/backlight/acpi_video0/brightness

and the brightness actually changes to something even darker. If I try to set it over 100, I get:

write error: Invalid argument

[Ubuntu QA Website (ubuntuqa)]

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
http://iso.qa.ubuntu.com/qatracker/reports/bugs/1821882

[Timo Aaltonen (tjaalton)]

Is this a regression from older releases?

when you say that disabling switchable graphics makes it use nvidia, I'd doubt that.. it should use intel then?

[Pierre Equoy (pieq)]

Sorry Timo, I had missed your last comment.

It's not a regression. The same thing happens on a 18.04.2 live session.

Please find attached a snapshot of the BIOS screen.

As you can see, there are two options:

- Enable Switchable Graphics (1)
- Discrete Graphics Controller Direct Output Mode (2)

I tried to start the 19.04 beta live USB in the four possible cases, here are the results:

 (1) | (2) | Comments
-----+-----+-------------------------------------------------------------------
 [ ] | [ ] | Issue described in original description
-----+-----+-------------------------------------------------------------------
 [ ] | [X] | Issue described in original description
-----+-----+-------------------------------------------------------------------
 [X] | [ ] | OK (/sys/class/backlight/ has only one element: "intel_backlight"
     | | Backlight can be adjusted with backlight keys
     | | `lspci` freezes, probably because of a nouveau bug
     | | Enough to install Ubuntu and switch to nvidia closed drivers
-----+-----+-------------------------------------------------------------------
 [X] | [X] | OK (/sys/class/backlight/ has only one element: "intel_backlight"
     | | Backlight can be adjusted with backlight keys
     | | `lspci` freezes, probably because of a nouveau bug
     | | Enough to install Ubuntu and switch to nvidia closed drivers
-----+-----+-------------------------------------------------------------------

[Pierre Equoy (pieq)]

With BIOS settings:

- Enable Switchable Graphics: DISABLED
- Discrete Graphics Controller Direct Output Mode: ENABLED

I booted into a 19.04 beta live session, then actiavted universe repos and installed acpica-tools. I then captured acpidump.

[Kai-Heng Feng (kaihengfeng)]

I tried _BCM for both its ACPI graphics devices, and it doesn't work whether "Enable Switchable Graphics" is enabled or not. So for this platform, the brightness is not controlled by its ACPI interface.

The nouveau backlight in use is nva3_bl_ops. Both its callback nva3_get_intensity() and nva3_set_intensity() correctly gets called by .get_brightness and .update_status, respectively.

The proprietary Nvidia driver registered "nvidia_0" in backlight sysfs and it can adjust brightness correctly. Skimming through its kernel source, the backlight is set by rm_set_backlight() which resides in the binary blob. Seems like we need to reverse engineer this to make it work under nouveau.