CODEWITHSUNDEEP
linuxembeddedkernelframebuffer
danatel
danatel

Reputation: 4982

Direct access to linux framebuffer - copyarea

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?

Upvotes: 7

Views: 9141

Answers (3)

SunnyShah
SunnyShah

Reputation: 30467

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 < 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) < 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) < 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);
}

};

Upvotes: 10

ACT
ACT

Reputation: 165

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.

Upvotes: 3

danatel
danatel

Reputation: 4982

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.

Upvotes: 1

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