Mmap maps physical addresses to user space

1. Application space void *virt_mem = Kzalloc (page_size, Gfp_kernel);
    2. Drive Layer----->> implement File_operation interface. Mmap method int Led_drv_mmap (struct file *filp, struct vm_area_struct *vma) {

    VMA is an information body, the user provides MMAP request//Parameter 1, VMA information carrier//parameter 2, User space virtual start position//Parameter 3, physical address unsigned long addr;

    if (((Vma->vm_end-vma->vm_start)!= page_size) | | vma->vm_pgoff) return-einval;

    Addr = Virt_to_phys (LED_DEV->VIRT_MEM);
    Vma->vm_flags |= Vm_io;    

    Vma->vm_page_prot = pgprot_noncached (Vma->vm_page_prot); if (Io_remap_pfn_range (VMA, Vma->vm_start, addr >> page_shift, page_size, Vma->vm_page_pro
        T)) {PRINTK (kern_err "%s:io_remap_pfn_range failed\n", __func__);
    Return-eagain;

     return 0; } 3.

    User layer of the dropped FD = open ("/dev/led0", O_RDWR);
    mmap int len = page_size; The return value is a mapped physical address char *mmap_addr = mmap (NULL, Len, prot_read| Prot_write, map_shared, FD, 0);

    Write a value to the inside memcpy (Mmap_addr,str,strlen (str));

    Sleep (1);
    Reading data read (FD, RBUF, 64);
 printf ("Rbuf =%s\n", rbuf);

2. String or Chinese to display the number of rows in the screen position, parameter 1:x axis coordinate parameter 2:y axis coordinate parameter 3: Display content size parameter 4: Display content void Display_character (unsigned int x,unsigned int
    y,unsigned int len,unsigned char *string) {int k, XX;
    unsigned char qh,wh;
    const unsigned char *mould;

    unsigned int length =len;
    printf ("Length =%d\n", length);         for (k=0,xx=x;k<length-1;k++) {if (string[k]&0x80)//Chinese character {QH =string[k]-0xa0;       Area code WH =string[k+1]-0xa0;
            Bit number mould =&__chs[((qh-1) *94+wh-1) *32];
            Draw_text16 (4+xx,y,0x0000ff,mould);
            xx+=16;
        k++;
            else {mould =&__ascii[string[k]*16];
            Draw_ascii (4+xx,y,0xff0000,mould);
        xx+=8; 
    3. Gets the physical space size of the vinfo.xres *VINFO.YRES*VINFO.BITS_PER_PIXEL/8 to the LCD screen and maps to the application layer static int init_lcd (char *dev_name) {
    int framebuffer_fd;
    /*1. Open frame Buffer device */FRAMEBUFFER_FD =open (DEV_NAME,O_RDWR); if (Framebuffer_fd<0) {printf ("Error:failed Open framebuffer device!\n");
    return-1; /*2. Gets the fixed parameter/if (IOCTL (Framebuffer_fd,fbioget_fscreeninfo,&finfo)) {printf ("error:failed get th
        E framebuffer device ' s fix informations!\n ");
    return-1; /*3. Gets the variable parameter/if (IOCTL (Framebuffer_fd,fbioget_vscreeninfo,&vinfo)) {printf ("error:failed get th
        E framebuffer device ' s var informations!\n ");
    return-1;
    printf ("Xres =%ld\n", vinfo.xres);
    printf ("Yres =%ld\n", vinfo.yres);
    ScreenSize = (vinfo.xres *vinfo.yres*vinfo.bits_per_pixel/8);


    printf ("ScreenSize =%ld\n", screensize); /*5. Mapping/framebuffer_ptr = (char *) mmap (null,//If this value is NULL, the kernel is used to automatically assign you a virtual space screens ize,//Space size prot_read| prot_write,//permission map_shared,//whether can be shared framebuffer_ FD,//FileDescriptor 0);
        from which place to start if (framebuffer_ptr<0) {printf ("error:failed to Mmap device mem!\n");
    return-1;
    } memset (Framebuffer_ptr,0,screensize);
    printf ("Framebuffer_ptr is mmaped ok!\n");
return FRAMEBUFFER_FD; } 4.
    /*1 the operation of the picture file. Open a picture * * pic_fd =open (ARGV[2],O_RDWR);

    printf ("pic_fd=%d\n", PIC_FD);
    /*2. Get picture size/Len =lseek (pic_fd, 0, seek_end);

    printf ("Len =%ld\n", Len);

    Buffer = (char *) malloc (len);
    Lseek (pic_fd, 0, Seek_set);

/*3. Read the picture data * * (Pic_fd,buffer,len); 5. If you want to display a picture picture file--read data--parse picture data--------data into RGB565---------------what data (RGB) void Draw_bmp (char *bmpfilename) is required for the LCD screen
    unsigned short *FB) {unsigned char * bmpdata;

    int ret;
    ret = Bmp_read_file (Bmpfilename, &bmpdata);
    if (ret) {printf ("read Bmpfile error.\n"); printf ("bmpread0000000!!!!
    \ n ");
    bmp2fb16_rgb565 (Bmpdata, FB); printf ("bm2fb1600000000000!!!!
\ n "); }