Changes between Version 19 and Version 20 of linux/media


Ignore:
Timestamp:
01/06/2021 07:49:15 PM (19 months ago)
Author:
Tim Harvey
Comment:

added section on HDMI display details

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  • linux/media

    v19 v20  
    597597[=#edid]
    598598== EDID
     599
     600=== Display Devices (HDMI sink)
     601In order to understand details about your display you can use the following:
     602{{{#!bash
     603# show kernel command-line to see what video params were passed
     604cat /proc/cmdline
     605# show HDMI monitor supported resolutions
     606cat /sys/class/drm/card1-HDMI-A-1/modes
     607# show current mode
     608cat /sys/class/graphics/fb0/modes
     609# read/parse EDID
     610get-edid | parse-edid
     611}}}
     612
     613=== Capture Devices (HDMI source)
    599614HDMI sources require an EDID from the HDMI sink (ie monitor/capture device) to know what formats are allowed. This is done on v4l2 capture devices such as the tda1997x by using the 'v4l2-ctl --set-edid' on the subdev for the capture device. The capture device will then provide this to the HDMI source (it wiggles its HPD line which is the equivalent of a hotplug) and then the HDMI source will provide the sink (capture device) with something compatible which you can then query. You can provide either a raw EDID binary file or a type which will cause the kernel to auto-generate a compatible EDID from.
    600615