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rockowitz / ddcutil

Control monitor settings using DDC/CI and USB
http://www.ddcutil.com
GNU General Public License v2.0
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DDC communication failed (getvcp of feature x10 returned Error_Info[DDCRC_RETRIES in ddc_write_read_with_retry, causes: DDCRC_DDC_DATA(15)]) #436

Open constambeys opened 1 month ago

constambeys commented 1 month ago

ddcutil interrogate

Examining device /dev/i2c-4... Obtain and interpret EDID using normal i2c functions ..... DDC communication succeeded

Do you know why interrogate works?

interrogate.log

rockowitz commented 1 month ago

Usually I suggest using options --ddcdata and -stats to see more details about the DDC data errors, but examining the journalctl section of the interrogate output I see the following line repeats: 

 Jul 22 18:30:32 dinos-pc-lan ddcutil[23299]: i2c_response_bytes: 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e 6e

So the response packet to DDC requests is corrupt. Why this is not the case with interrogate is unclear to me.

Your processor is relatively old (though not ancient). That may contribute to the problem.

If you have not already done so, try forcing a high sleep-multiplier using option --sleep-multiplier 2.0.

Finally, if you're comfortable building your own copy of the i915 driver, you could try making the changes described by Maciej Wójcik in this i915 feature request.