Bug 102931 - Radeon : EDID Reading Incorrectly
Summary: Radeon : EDID Reading Incorrectly
Status: RESOLVED INVALID
Alias: None
Product: Drivers
Classification: Unclassified
Component: Video(DRI - non Intel) (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: drivers_video-dri
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2015-08-15 13:08 UTC by Maxqia
Modified: 2015-08-17 09:34 UTC (History)
3 users (show)

See Also:
Kernel Version: 4.1.5
Subsystem:
Regression: No
Bisected commit-id:


Attachments
get-edid | parse-edid output (999 bytes, text/plain)
2015-08-17 07:19 UTC, Maxqia
Details

Description Maxqia 2015-08-15 13:08:30 UTC
When running get-edid | parse-edid with i2c-dev module loaded, It doesn't read my monitor correctly. The EDID reads fine with Windows and xrandr.
Comment 1 Alex Deucher 2015-08-17 02:02:31 UTC
IIRC, get-edid doesn't actually probe any i2c buses, it uses vm86 to do vbe calls to the vbios.  vbe will only provide the edid for whatever monitor it happened to probe at boot and likely won't work correctly once a real driver is loaded.  It's also not multi-head aware so if you have multiple monitors attached or are using a different display than what was available at boot it probably won't work.
Comment 2 Alex Deucher 2015-08-17 02:03:00 UTC
This is not a driver bug.  It's a limitation of get-edid.
Comment 3 Maxqia 2015-08-17 07:19:39 UTC
Created attachment 185121 [details]
get-edid | parse-edid output

According to the read-edid website and the program output, get-edid uses the i2c bus.
Comment 4 Christian König 2015-08-17 09:16:49 UTC
get-edid calls into the BIOS directly to access the I2C bus and doesn't uses the driver. With a kernel driver this is pretty much deprecated and shouldn't be used any more.

Use the one provided in sysfs instead, try: find /sys -name "edid"

Note You need to log in before you can comment on or make changes to this bug.