use efi framebuffer from linux user space

efi_fb.cc

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <stdint.h>
#include <unistd.h>

#include "genode.h"

#define EFIFB_ADDRESS 0xe0000000
#define FB_WIDTH 1920
#define FB_HEIGHT 0x14
#define FB_BYPP 4

void *get_mmio(off_t phys, size_t length)
{   
    int fd = open("/dev/genode-mmio", O_RDWR|O_SYNC);
    if(fd < 0){
        perror("open1 /dev/genode-mmio");
        return 0;
    }
    
    int fd2 = open("/dev/genode-mmio", O_RDWR|O_SYNC);
    if(fd2 < 0){
        perror("open2 /dev/genode-mmio");
    }
    
    mmio_range_t range = { (unsigned long) phys, length };
    
    if(ioctl(fd, MMIO_SET_RANGE, &range) < 0)
        perror("ioctl1");
    
    mmio_range_t range2 =  { 42, 42 };
    
    if(ioctl(fd2, MMIO_SET_RANGE, &range2) < 0)
        perror("ioctl2-1");
    
    if(ioctl(fd2, MMIO_SET_RANGE, &range2) < 0)
        perror("ioctl2-2");
    
    size_t pagesize = sysconf(_SC_PAGE_SIZE);
    off_t page_base = (phys / pagesize) * pagesize;
    off_t page_offset = phys - page_base;
    
    void *addr = mmap(NULL, page_offset + length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, phys);
    if(addr == MAP_FAILED){
        perror("mmap1");
        return 0;
    }
    
    void *addr2 = mmap(NULL, page_offset + length, PROT_READ | PROT_WRITE, MAP_SHARED, fd2, phys);
    if(addr2 == MAP_FAILED){
        perror("mmap2");
    }
    
    close(fd);
    close(fd2);
    
    return addr;
}

int main()
{
    uint32_t *buffer = (uint32_t*)get_mmio(EFIFB_ADDRESS, FB_WIDTH * FB_HEIGHT * FB_BYPP);
    printf("vga buffer: %p\n", buffer);

    uint32_t colors[4] = {0x00ffffff, 0x00ff0000, 0x0000ff00, 0x000000ff};

    if(buffer){
        int color = 0;
        while(1){
            printf("drawing color %#08x\n", colors[color]);
            for(size_t i = 0; i < FB_WIDTH * FB_HEIGHT; ++i){
                buffer[i] = colors[color];
            }
            color = (color + 1) % 4;
            sleep(2);
        }
    }
    return 0;
}