Direct access to linux framebuffer - copyarea

Question

I want to move very quickly a rectangle over a framebuffer in an embedded linux application. I have found that the function cfb_copyarea may be useful. But I cannot find any ioctl over the /dev/fb device to call the function. Or can this function be called directly?

score 10 · Answer 1 · edited Sep 26 '17 at 11:01

Here is a code to init and close FrameBuffer

class CFrameBuffer
{

void*   m_FrameBuffer;
struct  fb_fix_screeninfo m_FixInfo;
struct  fb_var_screeninfo m_VarInfo;
int     m_FBFD;

int InitFB()
{
    int iFrameBufferSize;
    /* Open the framebuffer device in read write */
    m_FBFD = open(FB_NAME, O_RDWR);
    if (m_FBFD &lt; 0) {
        printf("Unable to open %s.\n", FB_NAME);
        return 1;
    }
    /* Do Ioctl. Retrieve fixed screen info. */
    if (ioctl(m_FBFD, FBIOGET_FSCREENINFO, &m_FixInfo) &lt; 0) {
        printf("get fixed screen info failed: %s\n",
              strerror(errno));
        close(m_FBFD);
        return 1;
    }
    /* Do Ioctl. Get the variable screen info. */
    if (ioctl(m_FBFD, FBIOGET_VSCREENINFO, &m_VarInfo) &lt; 0) {
        printf("Unable to retrieve variable screen info: %s\n",
              strerror(errno));
        close(m_FBFD);
        return 1;
    }

    /* Calculate the size to mmap */
    iFrameBufferSize = m_FixInfo.line_length * m_VarInfo.yres;
    printf("Line length %d\n", m_FixInfo.line_length);
    /* Now mmap the framebuffer. */
    m_FrameBuffer = mmap(NULL, iFrameBufferSize, PROT_READ | PROT_WRITE,
                     MAP_SHARED, m_FBFD,0);
    if (m_FrameBuffer == NULL) {
        printf("mmap failed:\n");
        close(m_FBFD);
        return 1;
    }
    return 0;
}

void CloseFB()
{
    munmap(m_FrameBuffer,0);
    close(m_FBFD);
}

};

Than you for your answer. But this is not what I asked for. I do not want to move the pixels myself in the nmaped memory - I want to use kernel function cfb_copyarea for this. — danatel, Sep 13 '09 at 15:02
I like this answer. I created a test program based on this here: https://gist.github.com/1482697 — Rafal Rusin, Dec 15 '11 at 20:23
@RafalRusin: Thanks for sharing the program. It will be of much help to me. :) — Anoop K. Prabhu, Apr 29 '12 at 09:27

score 3 · Answer 2 · edited Dec 29 '10 at 05:02

3

Note that this code is not entirely correct, although it will work on many linux devices, on some it won't. To calculate the framebuffer size, do not do this:

iFrameBufferSize = m_FixInfo.line_length * m_VarInfo.yres;

Instead, do this:

iFrameBufferSize = m_FixInfo.smem_len;

And your code will be more portable.

edited Dec 29 '10 at 05:02

sth

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answered Dec 28 '10 at 19:52

ACT

165
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score 1 · Accepted Answer · answered Sep 15 '09 at 10:31

As far as I know after a few days of research, there is no ioctl for invoking this function. I have to write my own system call preferrably in a kernel module. Or copy the algorithm the from kernel source and use it in the user space via nmaped memory.

Direct access to linux framebuffer - copyarea

3 Answers3