How to get display info from EDID?

[Simon Que]

Is there currently any tool or library in CrOS to retrieve and parse EDID info from the display(s) connected to a Chrome OS device?

(We used to have xrandr for that but X has been removed. What has replaced xrandr?)

Simon

[Brian Norris]

Does 'modetest' give you what you need?

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[Bernie Thompson]

I believe the next closest we have is `modetest`.

-Bernie

On Wed, Jun 7, 2017 at 2:14 PM, Simon Que <sq...@chromium.org> wrote:

--

[Wilson, Brian]

Will this give you what you need?

 

Example is for the device’s eDP panel:

cd /sys/class/drm/card0-eDP/

hexdump –C edid

 

-Brian

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[Simon Que]

Yeah, pretty much.

My use case is to get the following info from DRM/EDID and put into a protobuf (or some other structured data format) to be sent to Chrome:

1. Model number
   
2. Manufacturer
   
3. Serial number
   
4. Output port on computer
   
5. Input port on display
   

Items 1-3 can be parsed from the raw EDID blob.

Item 4 can be obtained from the sysfs path.

Item 5, I'm not sure how to get.

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[Mark Hayter]

Some edid parsing tools made their way into libcras

https://chromium.googlesource.com/chromiumos/third_party/adhd/+/master/cras/src/common/

Not sure how much use they have had recently.

Mark

[Doug Anderson]

I always use a tool called "edid_decode". I think I had to track down
the source code and compile it myself since the version that Ubuntu
installed by default for me was old and had some big bugs. I don't
remember where I found it. I then use this absolutely awful python
code to convert a chunk of hex values into binary and pass it there.

---

#!/usr/bin/python

import sys
import binascii
import subprocess

if __name__ == '__main__':
s = sys.stdin.read()
s = s.replace(' ', '').replace('\n', '').replace('\t', '')
b = binascii.unhexlify(s)

print ", ".join("%#02x" % ord(c) for c in b)

p = subprocess.Popen(['/b/tip/scripts/edid_decode'],
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT)
out, _ = p.communicate(b)
print out

>>> email to chromium-os-d...@chromium.org.

[Tom Wai-Hong Tam (談偉航)]

There is a Python implementation edidparser under chameleon repo:

  https://chromium.googlesource.com/chromiumos/platform/chameleon/+/master/tools

Use it like:

 $ ./edidparser parse test_edid

And also some conversion tools:

 jsonedid: convert EDID binary to JSON

 jsonparser: convert JSON to EDID binary

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[Mike Frysinger]

there is also the read-edid project which is written in C.  it provides `get-edid` which uses raw i/o commands or Linux i2c to read the blob, and then passes it to `parse-edid` to do the actual display.  in our case, if the edid is available via sysfs files, could just run `parse-edid` on that directly.

-mike

[Dominik Behr]

You could read EDID from EDID blob property for the connector using DRM/KMS wrappers in Chrome. This probably would be the best way to make sure you are reading from correct connector/monitor. EDID format is pretty well described on Wikipedia and parsing it is not hard https://en.wikipedia.org/wiki/Extended_Display_Identification_Data