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The following bug was just posted: i915
failures with recent chips and docking stations and follows up
this thread
in the intel-gfx mailing list. Per suggestion of Jani Nikula of
Intel, I'm also posting a brief summary to this list. I am the developer of ddcutil, a Linux utility that manages monitor settings using DDC/CI. I am seeing a pattern of user error reports in which I2C communication is not working when a system with a recent Intel chip, using the i915 driver, is plugged into a docking station. ddcutil looks for displays by examining all non-SMBus /dev/i2c devices on the system. If checks for the presence of slave address x50 and x37. If they exist it tries to read the EDID on x50 and a Virtual Control Panel feature value on x37. Examining one of the user logs, I see that two /dev/i2c-n devices have udev sysattr name DPMST. When ddcutil probes those /dev/i2c devices, slave addresses x50 and x37 appear active, but reading the EDID fails. Per Jani Nikola, this is likely a bug in the core drm DP MST code. Sanford Rockowitz |
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