Boot logo replacement instructions

Introduction

The logo displayed at boot can be customized according to the client's preferences. For this, we have created a script that automates the process of replacing the logo.

Prerequisites

The image file must fulfill a number of requirements:

Bitmap (BMP file)
up to 577×432 resolution
indexed or 24bit RGB colors
uncompressed
preferably containing a simple logo on a black background with no additional padding.

Replace logo in an existing image

For devices supporting persistent bootlogo, it's possible to replace the logo without rebuilding firmware from scratch. You only need the firmware image and cbfstool.

Obtain cbfstool source code (skip if you've already cloned the coreboot source):
```
git clone https://github.com/Dasharo/coreboot.git
```

Build and install cbfstool:

cd coreboot/util/cbfstool
git checkout 912a262b7bf7cb49544f90cdb5c632b658918893
make
sudo make install

Remove the existing logo from the firmware image (replace [path] with the path to your firmware binary):
```
cbfstool [path] remove -r BOOTSPLASH -n logo.bmp
```
Add your desired bootlogo to the firmware image (replace [path] with the path to your firmware image and [logo] with the path to the logo):
```
cbfstool [path] add -f [logo] -r BOOTSPLASH -n logo.bmp -t raw -c lzma
```
Now you can flash the updated firmware image as usual. If you're not updating firmware and just changing the logo, only the BOOTSPLASH region needs to be updated. For example:
```
sudo flashrom -p internal --fmap -i BOOTSPLASH -w [path]
```