Changes between Version 19 and Version 20 of linux/media

Timestamp:

01/06/2021 07:49:15 PM (3 years ago)

Author:

Tim Harvey

Comment:

added section on HDMI display details

linux/media

@@ -597 +597 @@
 [=#edid]
 == EDID
+
+=== Display Devices (HDMI sink)
+In order to understand details about your display you can use the following:
+{{{#!bash
+# show kernel command-line to see what video params were passed
+cat /proc/cmdline
+# show HDMI monitor supported resolutions
+cat /sys/class/drm/card1-HDMI-A-1/modes
+# show current mode
+cat /sys/class/graphics/fb0/modes
+# read/parse EDID
+get-edid | parse-edid
+}}}
+
+=== Capture Devices (HDMI source)
 HDMI 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.