Open digitaltrails opened 3 months ago
This looks like another instance of stale value in /sys/class/drm/
Attachments:
1) Already connected and nvidia-settings
enabled ddcutil environment --verbose 2>&1 | tee boot-nvidia-config.log
2) Reboot and hotplug, enable Beng via nvidia-settings
then ddcutil environment --verbose 2>&1 | tee hotplug-nvidia-config.log
sdiff boot-nvidia-config.log hotplug-nvidia-config.log |less
...
Display 2 Display 2
I2C bus: /dev/i2c-4 I2C bus: /dev/i2c-4
DRM connector: card1-DP-2 <
/sys/class/drm/card1-DP-2/dpms On <
/sys/class/drm/card1-DP-2/enabled disabled <
/sys/class/drm/card1-DP-2/status connected <
Driver: Unknown Driver: Unknown
I2C address 0x50 (EDID) responsive: true I2C address 0x50 (EDID) responsive: true
I2C address 0x37 (DDC) responsive: true I2C address 0x37 (DDC) responsive: true
Is LVDS or EDP display: false Is LVDS or EDP display: false
Is laptop display by EDID: false Is laptop display by EDID: false
Is laptop display: false Is laptop display: false
/sys/bus/i2c/devices/i2c-4/name NVIDIA i2c ad /sys/bus/i2c/devices/i2c-4/name NVIDIA i2c ad
PCI device path: /sys/devices/ PCI device path: /sys/devices/
EDID synopsis: EDID synopsis:
Mfg id: BNQ - UNK Mfg id: BNQ - UNK
Model: BenQ T2200HD Model: BenQ T2200HD
Product code: 30502 (0x7726) Product code: 30502 (0x7726)
Serial number: 2C803527SL0 Serial number: 2C803527SL0
...
I did a hotplug of the Beng BegQ T2200HD, after which
libddcutil
correctly detected the new monitor, but an attempt to uselibddcutil
getvcp failed returningDDCRC_INTERNAL_ERROR
. The command-lineddcutil
worked fine, both with detect and setvcp.I traced this back to
src/ddc/ddc_displays.c
insideWhere it appear that the
drm_connector
was NULL:Suspecting the driver had not initialised some aspect of drm, I then hacked the call to
ddc_validate_display_ref
to forcebasic_only
, and then the setvcp worked.I then rebooted figuring drm would then be correctly initialised. Sure enough the
basic_only
hack was no longer required, a getvcp via libddcutil worked just fine.I don't think you can trust the drm structures if the Nvidia driver is in play. I suppose this could be covered off with documentation. Or maybe an option to completely switch off drm.