raspi3-tutorial/09_framebuffer/lfb.c

/*
 * Copyright (C) 2018 bzt (bztsrc@github)
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy,
 * modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 */

#include "uart.h"
#include "mbox.h"
#include "homer.h"
#include "delays.h"

unsigned int width, height, pitch, isrgb;   /* dimensions and channel order */
unsigned char *lfb;                         /* raw frame buffer address */

/**
 * Set screen resolution to 1024x768
 */
void lfb_init()
{
    /* newer qemu segfaults if we don't wait here a bit */
    wait_msec(100000);

    mbox[0] = 35*4;
    mbox[1] = MBOX_REQUEST;

    mbox[2] = 0x48003;  //set phy wh
    mbox[3] = 8;
    mbox[4] = 8;
    mbox[5] = 1024;         //FrameBufferInfo.width
    mbox[6] = 768;          //FrameBufferInfo.height

    mbox[7] = 0x48004;  //set virt wh
    mbox[8] = 8;
    mbox[9] = 8;
    mbox[10] = 1024;        //FrameBufferInfo.virtual_width
    mbox[11] = 768;         //FrameBufferInfo.virtual_height

    mbox[12] = 0x48009; //set virt offset
    mbox[13] = 8;
    mbox[14] = 8;
    mbox[15] = 0;           //FrameBufferInfo.x_offset
    mbox[16] = 0;           //FrameBufferInfo.y.offset

    mbox[17] = 0x48005; //set depth
    mbox[18] = 4;
    mbox[19] = 4;
    mbox[20] = 32;          //FrameBufferInfo.depth

    mbox[21] = 0x48006; //set pixel order
    mbox[22] = 4;
    mbox[23] = 4;
    mbox[24] = 1;           //RGB, not BGR preferably

    mbox[25] = 0x40001; //get framebuffer, gets alignment on request
    mbox[26] = 8;
    mbox[27] = 8;
    mbox[28] = 4096;        //FrameBufferInfo.pointer
    mbox[29] = 0;           //FrameBufferInfo.size

    mbox[30] = 0x40008; //get pitch
    mbox[31] = 4;
    mbox[32] = 4;
    mbox[33] = 0;           //FrameBufferInfo.pitch

    mbox[34] = MBOX_TAG_LAST;

    //this might not return exactly what we asked for, could be
    //the closest supported resolution instead
    if(mbox_call(MBOX_CH_PROP) && mbox[20]==32 && mbox[28]!=0) {
        mbox[28]&=0x3FFFFFFF;   //convert GPU address to ARM address
        width=mbox[5];          //get actual physical width
        height=mbox[6];         //get actual physical height
        pitch=mbox[33];         //get number of bytes per line
        isrgb=mbox[24];         //get the actual channel order
        lfb=(void*)((unsigned long)mbox[28]);
    } else {
        uart_puts("Unable to set screen resolution to 1024x768x32\n");
    }
}

/**
 * Show a picture
 */
void lfb_showpicture()
{
    int x,y;
    unsigned char *ptr=lfb;
    char *data=homer_data, pixel[4];

    ptr += (height-homer_height)/2*pitch + (width-homer_width)*2;
    for(y=0;y<homer_height;y++) {
        for(x=0;x<homer_width;x++) {
            HEADER_PIXEL(data, pixel);
            // the image is in RGB. So if we have an RGB framebuffer, we can copy the pixels
            // directly, but for BGR we must swap R (pixel[0]) and B (pixel[2]) channels.
            *((unsigned int*)ptr)=isrgb ? *((unsigned int *)&pixel) : (unsigned int)(pixel[0]<<16 | pixel[1]<<8 | pixel[2]);
            ptr+=4;
        }
        ptr+=pitch-homer_width*4;
    }
}