Howto disable HDMI audio only with Debian Jessie on BBB

[kritzel...@gmx.de]

Just upgraded my BBB from factory image to Debian Jessie: https://debian.beagleboard.org/images/bone-debian-8.6-lxqt-4gb-armhf-2016-11-06-4gb.img.xz

With the old Wheezy image and the concept of virtual HDMI capes it was possible to disable HDMI audio while keeping HDMI video alive (uENv.txt: cape_disable=capemgr.disable_partno=BB-BONELT-HDMI). This step released all preallocated mcasp0-pins for other applications, e.g. for PRU0 access, while still having an HDMI display attached and running.

Now with Jessie (no more virtual capes) I have difficulties to realize such a scenario. Apparently there is no preconfigured DTB with capemgr, eMMC and HDMI enabled, but Audio disabled (see http://elinux.org/BeagleBone_DTBs). Also the last table at this page (http://elinux.org/Beagleboard:BeagleBone_Debian_Image_Migration) shows nothing more than a question mark for that particular case.

Does anyone have a suitable DTB (or *.dts) at hand or can point me to information how to generate such a file from existing device tree source files?

Thanks,
KK

[Tarmo Kuuse]

I'd like to bump this topic. Any pointers on how to disable HDMI audio only?

I'd like to mux some audio pins (P9.25) to GPIO, but they are snatched by the mcasp driver on boot and it won't give them back. Doing something like "cape_disable=bone_capemgr.disable_partno=BB-BONELT-HDMIN" doesn't seem to release the audio pins. 

At the same I would also need to use the (super useful) on-board eMMC and HDMI video output.

If there's no pre-made solution, I'd probably have to figure out how to hack the boot-time device tree, and that looks like a rather daunting task.

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Kind regards,

Tarmo Kuuse