raspberry3_bare/fb.c

#include "fb.h"
#include "mbox.h"
#include "uart.h"
#include "utils.h"
#include <stdint.h>

#define MBOX_TAG_FBALLOC 0x40001
#define MBOX_TAG_FBGETPITCH 0x40008
#define MBOX_TAG_FBSETPHYS 0x48003
#define MBOX_TAG_FBSETVIRT 0x48004
#define MBOX_TAG_FBSETDEPTH 0x48005
#define MBOX_TAG_FBSETPIXORD 0x48006
#define MBOX_TAG_FBSETOFF 0x48009

unsigned char *init_fb(struct fbst *fb) {
  // sending many tags at once
  mbox[0] = 35 * 4;
  mbox[1] = MBOX_REQUEST;
  mbox[2] = MBOX_TAG_FBSETPHYS; // set phy wh
  mbox[3] = 8;
  mbox[4] = 0;
  mbox[5] = 1920;    // FrameBufferInfo.width
  mbox[6] = 1080;    // FrameBufferInfo.height
  mbox[7] = MBOX_TAG_FBSETVIRT; // set virt wh
  mbox[8] = 8;
  mbox[9] = 0;
  mbox[10] = 1920;    // FrameBufferInfo.virtual_width
  mbox[11] = 1080;    // FrameBufferInfo.virtual_height
  mbox[12] = MBOX_TAG_FBSETOFF; // set virt offset
  mbox[13] = 8;
  mbox[14] = 0;
  mbox[15] = 0;       // FrameBufferInfo.x_offset
  mbox[16] = 0;       // FrameBufferInfo.y.offset
  mbox[17] = MBOX_TAG_FBSETDEPTH; // set depth
  mbox[18] = 4;
  mbox[19] = 0;
  mbox[20] = 32;      // FrameBufferInfo.depth
  mbox[21] = MBOX_TAG_FBSETPIXORD; // set pixel order
  mbox[22] = 4;
  mbox[23] = 0;
  mbox[24] = 1;       // RGB, not BGR preferably
  mbox[25] = MBOX_TAG_FBALLOC; // get framebuffer, gets alignment on request
  mbox[26] = 8;
  mbox[27] = 0;
  mbox[28] = 4096;    // FrameBufferInfo.pointer
  mbox[29] = 0;       // FrameBufferInfo.size
  mbox[30] = MBOX_TAG_FBGETPITCH; // get pitch
  mbox[31] = 4;
  mbox[32] = 0;
  mbox[33] = 0; // FrameBufferInfo.pitch
  mbox[34] = MBOX_TAG_LAST;

  if (mbox_call(MBOX_CH_PROP, mbox) == 0 && mbox[20] == 32 && mbox[28] != 0) {
    mbox[28] &= 0x3FFFFFFF; // convert GPU address to ARM address
    fb->width = mbox[5];    // get actual physical width
    fb->height = mbox[6];   // get actual physical height
    fb->pitch = mbox[33];   // get number of bytes per line
    fb->isrgb = mbox[24];   // get the actual channel order
    fb->fbp = (void *)((unsigned long)mbox[28]);
  } else {
    puts("Unable to set framebuffer!\r\n");
    return 0;
  }

  return fb->fbp;
}