# Changing u-boot input devices config for RPi4 in Yocto?

**URL:** <https://hub.mender.io/t/changing-u-boot-input-devices-config-for-rpi4-in-yocto/7069>\
**Category:** General Discussions\
**Created:** [August 2, 2024, 7:46am UTC](https://hub.mender.io/t/changing-u-boot-input-devices-config-for-rpi4-in-yocto/7069 "2024-08-02T07:46:57Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![dpv](https://avatars.discourse-cdn.com/v4/letter/d/b4bc9f/32.png) [@dpv](https://hub.mender.io/u/dpv)\
**Post date:** [August 2, 2024, 7:46am UTC](https://hub.mender.io/t/changing-u-boot-input-devices-config-for-rpi4-in-yocto/7069/1 "2024-08-02T07:46:57Z")

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We’ve integrated Mender 3.5 on our Raspberry Pi 4 Yocto project.

We would like to make changes to u-boot’s configuration. Specifically, we want to disable certain input sources/devices such as serial/uart0, keyboard, etc.

I’m aware `boot.scr` and `uEnv.txt` are typically involved, but after adding mender and u-boot to a RPi4 Yocto build, what is the preferred method of doing this?

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**Author:** ![TheYoctoJester](https://yyz2.discourse-cdn.com/flex036/user_avatar/hub.mender.io/theyoctojester/32/1444_2.png) [@TheYoctoJester](https://hub.mender.io/u/TheYoctoJester)\
**Post date:** [August 5, 2024, 1:31pm UTC](https://hub.mender.io/t/changing-u-boot-input-devices-config-for-rpi4-in-yocto/7069/2 "2024-08-05T13:31:10Z")

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Hi @dpv,

I don’t think you can sufficiently affect `u-boot` to ignore the serial port and keyboard by boot scripts - effectively you need to do proper hardening. The first thing to look at would be the `u-boot` configuration, if I remember correctly it has a straightforward way to limit the serial terminal to a magic string/key for dropping into it. If you completely want to disable it, source code modifications might be required.

Greets,  
Josef