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    <p>Use <code><a href="http://www.manpagez.com/man/2/open/" rel="noreferrer">open()</a></code> on the right file in <code>/dev</code> (eg. <code>/dev/fb0</code>), then use <code><a href="http://www.manpagez.com/man/2/mmap/" rel="noreferrer">mmap()</a></code> to map it into memory. Manpages will help for these syscalls if you do not know how to use them.</p> <p>Then there are some structures and constants for some <code><a href="http://www.manpagez.com/man/2/ioctl/" rel="noreferrer">ioctl()</a></code>s in <code>&lt;linux/fb.h&gt;</code>. Like many kernel headers, you can learn a lot simply browsing the file.</p> <p>Particularly interesting is the ioctl <code>FBIOGET_VSCREENINFO</code> with <code>struct fb_var_screeninfo</code>. Note this has <code>xres</code>, <code>yres</code> (resolution) and <code>bits_per_pixel</code>. Then there's <code>FBIOGET_FSCREENINFO</code> and <code>struct fb_fix_screeninfo</code> which has further information like <code>type</code> and <code>line_length</code>.</p> <p>So a pixel at (x, y) might be at <code>mmap_base_address + x * bits_per_pixel/8 + y * line_length</code>. The exact format of the pixels will depend on the structures you retrieve via ioctl; it's your job to decide how to read/write them.</p> <p>It's been a while since I've worked with this so I'm a bit hazy on more details..</p> <p>Here's a quick and dirty code sample just to illustrate how it's done... I haven't tested this.</p> <pre><code>#include &lt;sys/types.h&gt; #include &lt;sys/ioctl.h&gt; #include &lt;sys/mman.h&gt; #include &lt;linux/fb.h&gt; #include &lt;unistd.h&gt; #include &lt;fcntl.h&gt; #include &lt;stdio.h&gt; int main() { struct fb_var_screeninfo screen_info; struct fb_fix_screeninfo fixed_info; char *buffer = NULL; size_t buflen; int fd = -1; int r = 1; fd = open("/dev/fb0", O_RDWR); if (fd &gt;= 0) { if (!ioctl(fd, FBIOGET_VSCREENINFO, &amp;screen_info) &amp;&amp; !ioctl(fd, FBIOGET_FSCREENINFO, &amp;fixed_info)) { buflen = screen_info.yres_virtual * fixed_info.line_length; buffer = mmap(NULL, buflen, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); if (buffer != MAP_FAILED) { /* * TODO: something interesting here. * "buffer" now points to screen pixels. * Each individual pixel might be at: * buffer + x * screen_info.bits_per_pixel/8 * + y * fixed_info.line_length * Then you can write pixels at locations such as that. */ r = 0; /* Indicate success */ } else { perror("mmap"); } } else { perror("ioctl"); } } else { perror("open"); } /* * Clean up */ if (buffer &amp;&amp; buffer != MAP_FAILED) munmap(buffer, buflen); if (fd &gt;= 0) close(fd); return r; } </code></pre>
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    1. POHow to draw the graph in framebuffer using c language..?
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    1. COjust realized I forgot about line_length in the "finfo" struct, so updating..
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    2. COWhen i compile i am getting some errors like this, In file included from g.c:4: /usr/include/sys/mman.h:38: error: conflicting types for ‘mode_t' /usr/include/linux/types.h:15: error: previous declaration of ‘mode_t' was here In file included from g.c:5: /usr/include/unistd.h:203: error: conflicting types for ‘gid_t' /usr/include/linux/types.h:27: error: previous declaration of ‘gid_t' was here /usr/include/unistd.h:208: error: conflicting types for ‘uid_t' /usr/include/linux/types.h:26: error: previous declaration of ‘uid_t' was here In file included from /usr/include/bits/fcntl.h:25,
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    3. CO@Rahul - Must be the order I put the headers in... Maybe try sys/types.h first?
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