Framebuffer mechanism: Framebuffer is a general-purpose, hardware-independent interface that maps the pixel data in the video memory of the graphics card to the buffer in the kernel space . The application program realizes graphics display by accessing the buffer , and can use the control interface to set the resolution rate, adjust color depth, etc.
The Framebuffer device is a standard character device with a major device number of 29, which corresponds to the /dev/fbn device file.