Change input with 2 cards and VGA passthrough #82
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What you're trying to do sometimes works, sometimes doesn't. It seems to
depend on the monitor's DDC/CI implementation - whether DDC
communication is active on the inactive video input.
Some things you might try:
- Avoid using DisplayPort. I2C on DVI and HDMI uses dedicated pins,
whereas I2C on DIsplayPort is emulated over the Aux channel.
- Reference the display by its i2c bus number, e.g. "sudo ddcutil --bus
6 setvcp 60 x0f"
- Use a Windows program within the VM to switch back
The latter almost always works. I suggest using softMCCS
<https://www.entechtaiwan.com/lib/softmccs.shtm> from EnTech, at least
for testing. Once you know that works you can look for a simpler
Windows command line utility to perform the switching.
One thing that has me a bit perplexed is that there appears to be only 1
monitor (the BL2400) connected to the system. How are you issuing Linux
commands when the monitor is switched to Windows?
If you run command "sudo ddcutil environment --verbose" and send the
output as an attachment it will help me better understand your
configuration.
Sanford
…On 4/11/19 7:25 AM, v44r wrote:
I have a BenQ BL2400. The DP-1 input is connected to an Intel GPU, the
DVI-1 input is connected to an AMD GPU that I passthrough to a Windows
virtual machine.
I'd like to switch inputs with a keyboard shortcut that I have set in
the window manager in linux. When I'm in linux (Intel==>DP-1 input
selected) I can switch to DVI-1 (AMD GPU==>Windows) without problems.
This is the output of ddcutil detect while in linux before switching:
|# sudo ddcutil detect Display 1 I2C bus: /dev/i2c-6 EDID synopsis:
Mfg id: BNQ Model: BenQ BL2400 Serial number: 49A02042SL0 Manufacture
year: 2010 EDID version: 1.4 VCP version: 2.1 |
However, while I'm showing Windows (DVI-1) if I run the same command
from a linux terminal, I get:
|# sudo ddcutil detect Invalid display I2C bus: /dev/i2c-6 EDID
synopsis: Mfg id: BNQ Model: BenQ BL2400 Serial number: 49A02042SL0
Manufacture year: 2010 EDID version: 1.4 DDC communication failed |
and I cannot switch back with ddcutil. If I switch manually (with the
button) to DP-1 and run ddcutil again the following executions are
even worse:
|# sudo ddcutil detect No displays found |
and I have to turn the monitor off and on to be able to control it again.
Maybe windows is messing with DDC? Is it a bad idea to try to do what
I'm doing? Should I search for a windows utility to change back to
linux in DP-1 or is it better to not even try to mess with DDC from
two running OSs?
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Thanks for the tips.
I can change the keyboard focus from linux to windows and vice-versa pressing both Ctrl keys. So even when I'm showing windows I can (blindly) run linux commands. I run the command, nothing happens, so I switch inputs with the physical button and see the resulting error. I tried switching DP and DVI (i.e. using DVI for linux and DP for windows) and using the bus number instead of the display number (/dev/i2c-4 right now), but I get the same result: when I change from linux (DVI) to windows (DP) no errors: and the monitor switches inputs accordingly. But when I try to switch back (I'm showing windows but linux has keyboard focus, so I run this blind): So, as you say, it seems that the monitor ignores DCC commands from non-selected inputs. With environment verbose, when the input connected to the linux graphics card is selected (currently DVI): but when another input is selected: I ended up installing ClickMonitorDDC in windows, which has a nice interface and support for hotkeys and assigned a combination to switch back to linux. Now I can switch back and forth without problems. (edit) full log |
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Thanks for the update. I'm glad you got it working.
Can I ask you to run "sudo ddcutil interrogate" and send me the output
as a file? I'd like to add a description of your monitor to the list at
http://www.ddcutil.com/monitor_notes/
Sanford
…On 4/12/19 6:20 AM, v44r wrote:
Thanks for the tips.
One thing that has me a bit perplexed is that there appears to be
only 1 monitor (the BL2400) connected to the system. How are you
issuing Linux commands when the monitor is switched to Windows?
I can change the keyboard focus from linux to windows and vice-versa
pressing both Ctrl keys. So even when I'm showing windows I can
(blindly) run linux commands. I run the command, nothing happens, so I
switch inputs with the physical button and see the resulting error.
I tried switching DP and DVI (i.e. using DVI for linux and DP for
windows) and using the bus number instead of the display number
(/dev/i2c-4 right now), but I get the same result: when I change from
linux (DVI) to windows (DP) no errors:
|$ sudo ddcutil -b 4 setvcp 60 0x0f $ |
and the monitor switches inputs accordingly. But when I try to switch
back (I'm showing windows but linux has keyboard focus, so I run this
blind):
|$ sudo ddcutil -b 4 setvcp 60 0x03 DDC communication failed for
monitor on I2C bus /dev/i2c-4 $ |
So, as you say, it seems that the monitor ignores DCC commands from
non-selected inputs. With environment verbose, when the input
connected to the linux graphics card is selected (currently DVI):
|Trying simple VCP read of feature 0x10... read() returned 6e 88 02 00
No protocol specified 10 00 00 64 00 1e de Attempt 1 to read feature
succeeded. DDC communication succeeded |
but when another input is selected:
|Trying simple VCP read of feature 0x10... read() returned de de de de
No protocol specified de de de de de de de Attempt 1 to read feature
failed. status = DDCRC_DDC_DATA(-3001): DDC data error. Retrying...
read() returned de de de de de de de de de de de Attempt 2 to read
feature failed. status = DDCRC_DDC_DATA(-3001): DDC data error.
Retrying... read() returned de de de de de de de de de de de Attempt 3
to read feature failed. status = DDCRC_DDC_DATA(-3001): DDC data
error. DDC communication failed. |
I ended up installing ClickMonitorDDC in windows, which has a nice
interface and support for hotkeys and assigned a combination to switch
back to linux. Now I can switch back and forth without problems.
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im having this same issue: my issue is that i cant switch back from windows via ClickMonitorDDC or softMCCS which says it cant find DCC/CI: softMCCS.log interrogate log: ddcutil-interrogate.log |
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I have a BenQ BL2400. The DP-1 input is connected to an Intel GPU, the DVI-1 input is connected to an AMD GPU that I passthrough to a Windows virtual machine.
I'd like to switch inputs with a keyboard shortcut that I have set in the window manager in linux. When I'm in linux (Intel==>DP-1 input selected) I can switch to Windows (AMD GPU==>DVI-1) without problems. This is the output of ddcutil detect while in linux before switching:
However, while I'm showing Windows (DVI-1) if I run the same command from a linux terminal, I get:
and I cannot switch back with ddcutil. If I switch manually (with the button) to DP-1 and run ddcutil again the following executions are even worse:
and I have to turn the monitor off and on to be able to control it again.
Maybe windows is messing with DDC? Is it a bad idea to try to do what I'm doing? Should I search for a windows utility to change back to linux in DP-1 or is it better to not even try to mess with DDC from two running OSs?
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