Device Tree in android

Hi
i am using android 3.8 (andrew henderson build)
i have some questions on how to act with device tree over it :

1- where to find the available device trees ?
in angstrom the .dts & .dtbo files are exist in /lib/firmware
but in android i didn’t find any folder that contain the dts or dtbo files , so where can i find them ?

2- how to disable hdmi ?
i try to append the following line to uENV.txt

capemgr.disable_partno=BB-BONELT-HDMI

but it dosen’t work .

3- i want to enable lcd 7 cape manually how can i do that ?
in angstrom i do that by the following echo command :

echo BB-BONE-LCD7-01 > /sys/devices/bone_capemgr.8/slots

but in android it also doesn’t work .

please help .

Thanks

  1. In that Android image, device tree overlay files are copied into the /system/vendor/firmware directory of the root file system.

  2. To disable HDMI, you must disable both the HDMI (video and audio) and HDMIN (video only) capes:

capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN

  1. The overlay fragments of the “default” capes (LCD3/4/7, HDMI, eMMC, etc.) are compiled into the kernel itself. They do not need to be copied into /system/vendor/firmware. Only your own custom .dtbo files need to be copied into the firmware diretory. If the LCD7 cape is plugged into the BBB at boot, it will be detected via the capebus manager in the kernel and the LCD7 cape’s overlay will be automatically enabled. The only thing that you will need to do to use the LCD7 cape is to remove the “video=” option from the kernel command line arguments in the uEnv.txt file and have the LCD7 cape plugged in at boot. The resolution will be pulled automatically from the cape overlay, so you don’t specify it on the kernel command line.

Cape overlays have a priority to their loading order on the cape bus. In your case, the LCD capes have a higher priority than that of the HDMI. If you plug in the LCD7 cape and turn the BBB on, the LCD7 cape gets control of the LCDC pins. The HDMI and HDMIN capes will then fail to load because they both request the use of the LCDC pins, so HDMI is disabled automatically when the LCD7 cape is in use.

Echo-ing the name of a device tree overlay into the bone_capemgr does work for loading overlays, but only for custom .dtbo files that you copy into /system/vendor/firmware (rather than /lib/firmware under Linux).

Andrew

Hi Samer and Andrew,

I have the same quetions as Samer’s. I’m glad I can find some answer here, but I still have further questions below. Could you provide your suggestions?

  1. I didn’t see any *.dtbo file in /system/vendor/firmware. Here is what I see.
    shell@beagleboneblack:/system/vendor/firmware $ ls
    cpia2
    edgeport
    emi26
    emi62
    kaweth
    keyspan_pda
    mts_cdma.fw
    mts_edge.fw
    mts_gsm.fw
    ti_3410.fw
    ti_5052.fw
    whiteheat.fw
    whiteheat_loader.fw
    yam

  2. I put “optargs=quiet capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN” in uENV.txt, but I got "Unknown command ‘optargs=quiet’ " in the putty.

  3. Where can I find the default LCD7 dtbo file? I would like to echo it to drive my custum LCD. I have a LCD which has the same pin assignment, but it does not have EEPROM. BBB will not detect it so I need to echo the dtbo file.

Regards,
Jimmy