Request for help with errors after compilation

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1

Hello,
I would like to make a graphical interface with lvgl. I followed the different steps for starting a project. But when compiling, the following errors appear:
error: ‘DISP_BUF_SIZE’ undeclared (first use in this function)
error: ‘fbdev_flush’ undeclared (first use in this function)

Cordially

2

What steps have you used to get started? These are the ones for a fresh project - they don’t mention DISP_BUF_SIZE or fbdev_flush.