mmap.html

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 */</span>
<span class="kw4">static</span> <span class="kw4">int</span> simple_release<span class="br0">&#40;</span><span class="kw4">struct</span> inode *inode, <span class="kw4">struct</span> file *filp<span class="br0">&#41;</span>
<span class="br0">&#123;</span>
	<span class="kw1">return</span> <span class="nu0">0</span>;
<span class="br0">&#125;</span>
&nbsp;
&nbsp;
&nbsp;
<span class="coMULTI">/*
 * Common VMA ops.
 */</span>
&nbsp;
<span class="kw4">void</span> simple_vma_open<span class="br0">&#40;</span><span class="kw4">struct</span> vm_area_struct *vma<span class="br0">&#41;</span>
<span class="br0">&#123;</span>
	printk<span class="br0">&#40;</span><span class="st0">"Simple VMA open, virt %lx, phys %lx<span class="es0">\n</span>"</span>,
			vma-&gt;vm_start, vma-&gt;vm_pgoff &lt;&lt; PAGE_SHIFT<span class="br0">&#41;</span>;
<span class="br0">&#125;</span>
&nbsp;
<span class="kw4">void</span> simple_vma_close<span class="br0">&#40;</span><span class="kw4">struct</span> vm_area_struct *vma<span class="br0">&#41;</span>
<span class="br0">&#123;</span>
	printk<span class="br0">&#40;</span><span class="st0">"Simple VMA close.<span class="es0">\n</span>"</span><span class="br0">&#41;</span>;
<span class="br0">&#125;</span>
&nbsp;
&nbsp;
<span class="coMULTI">/*
 * The remap_pfn_range version of mmap.  This one is heavily borrowed
 * from drivers/char/mem.c.
 */</span>
&nbsp;
<span class="kw4">static</span> <span class="kw4">struct</span> vm_operations_struct simple_remap_vm_ops = <span class="br0">&#123;</span>
	.<span class="me1">open</span> =  simple_vma_open,
	.<span class="me1">close</span> = simple_vma_close,
<span class="br0">&#125;</span>;
&nbsp;
<span class="kw4">static</span> <span class="kw4">int</span> simple_remap_mmap<span class="br0">&#40;</span><span class="kw4">struct</span> file *filp, <span class="kw4">struct</span> vm_area_struct *vma<span class="br0">&#41;</span>
<span class="br0">&#123;</span>
&nbsp;
	<span class="coMULTI">/* In this sample we are using _ramend -&gt; physical_mem_end as the buffer to
	   be mmaped. */</span>
	<span class="kw2">extern</span> <span class="kw4">unsigned</span> <span class="kw4">long</span> physical_mem_end;
	<span class="kw2">extern</span> <span class="kw4">int</span> _ramend;
&nbsp;
	<span class="coMULTI">/* the kernel passes in the vm_pgoff - the offset, in *pages*
	 * from the start of the buffer that the user space app wants
	 * to mmap. This is the last arg in the user space mmap call.
	 * We check it to make sure it is not out of bounds.
	 */</span>
	<span class="kw1">if</span> <span class="br0">&#40;</span>vma-&gt;vm_pgoff &gt; <span class="br0">&#40;</span><span class="br0">&#40;</span>physical_mem_end  - _ramend<span class="br0">&#41;</span> &gt;&gt; PAGE_SHIFT<span class="br0">&#41;</span><span class="br0">&#41;</span> <span class="br0">&#123;</span>
		<span class="kw1">return</span> -EINVAL;
	<span class="br0">&#125;</span>
&nbsp;
	vma-&gt;vm_start = <span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">long</span><span class="br0">&#41;</span>_ramend;
	vma-&gt;vm_end = <span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">long</span><span class="br0">&#41;</span>physical_mem_end;
&nbsp;
	<span class="coMULTI">/* before remap is called, pgoff must be set to the kernel page
	 * offset from zero. Do to this, we figure out the address,
	 * ( &lt;&lt; PAGE_SHIFT ), add it to the start of the buffer, and
	 * turn that back to pages (&gt;&gt; PAGE_SHIFT)
	 */</span>
	vma-&gt;vm_pgoff = <span class="br0">&#40;</span><span class="br0">&#40;</span>vma-&gt;vm_pgoff &lt;&lt; PAGE_SHIFT <span class="br0">&#41;</span> +
			 <span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">long</span><span class="br0">&#41;</span>_ramend <span class="br0">&#41;</span> &gt;&gt; PAGE_SHIFT;
&nbsp;
&nbsp;
	<span class="coMULTI">/*   VM_MAYSHARE limits for mprotect(), and must be set on nommu.
	 *   Other flags can be set, and are documented in
	 *   include/linux/mm.h
	 */</span>
	vma-&gt;vm_flags |=  VM_MAYSHARE;
&nbsp;
	<span class="kw1">if</span> <span class="br0">&#40;</span>remap_pfn_range<span class="br0">&#40;</span>vma, vma-&gt;vm_start, vma-&gt;vm_pgoff,
			    vma-&gt;vm_end - vma-&gt;vm_start,
			    vma-&gt;vm_page_prot<span class="br0">&#41;</span><span class="br0">&#41;</span>
		<span class="kw1">return</span> -EAGAIN;
&nbsp;
	vma-&gt;vm_ops = &amp;simple_remap_vm_ops;
	simple_vma_open<span class="br0">&#40;</span>vma<span class="br0">&#41;</span>;
	<span class="kw1">return</span> <span class="nu0">0</span>;
<span class="br0">&#125;</span>
&nbsp;
ssize_t simple_read <span class="br0">&#40;</span><span class="kw4">struct</span> file *filp, <span class="kw4">char</span> __user *buf, size_t count,
                loff_t *f_pos<span class="br0">&#41;</span>
<span class="br0">&#123;</span>
	<span class="kw1">return</span> count;
<span class="br0">&#125;</span>
&nbsp;
<span class="coMULTI">/*
 * Set up the cdev structure for a device.
 */</span>
<span class="kw4">static</span> <span class="kw4">void</span> simple_setup_cdev<span class="br0">&#40;</span><span class="kw4">struct</span> cdev *dev, <span class="kw4">int</span> minor,
		<span class="kw4">struct</span> file_operations *fops<span class="br0">&#41;</span>
<span class="br0">&#123;</span>
	<span class="kw4">int</span> err, devno = MKDEV<span class="br0">&#40;</span>simple_major, minor<span class="br0">&#41;</span>;
&nbsp;
	cdev_init<span class="br0">&#40;</span>dev, fops<span class="br0">&#41;</span>;
	dev-&gt;owner = THIS_MODULE;
	dev-&gt;ops = fops;
	err = cdev_add <span class="br0">&#40;</span>dev, devno, <span class="nu0">1</span><span class="br0">&#41;</span>;
	<span class="coMULTI">/* Fail gracefully if need be */</span>
	<span class="kw1">if</span> <span class="br0">&#40;</span>err<span class="br0">&#41;</span>
		printk <span class="br0">&#40;</span>KERN_NOTICE <span class="st0">"Error %d adding simple%d"</span>, err, minor<span class="br0">&#41;</span>;
<span class="br0">&#125;</span>
&nbsp;
&nbsp;
<span class="coMULTI">/*
 * Our various sub-devices.
 */</span>
<span class="coMULTI">/* Device 0 uses remap_pfn_range */</span>
<span class="kw4">static</span> <span class="kw4">struct</span> file_operations simple_remap_ops = <span class="br0">&#123;</span>
	.<span class="me1">owner</span>   = THIS_MODULE,
	.<span class="me1">open</span>    = simple_open,
	.<span class="me1">read</span>    = simple_read,
	.<span class="me1">release</span> = simple_release,
	.<span class="me1">mmap</span>    = simple_remap_mmap,
<span class="br0">&#125;</span>;
&nbsp;
<span class="co2">#define MAX_SIMPLE_DEV 1</span>
&nbsp;
<span class="coMULTI">/*
 * We export two simple devices.  There's no need for us to maintain any
 * special housekeeping info, so we just deal with raw cdevs.
 */</span>
<span class="kw4">static</span> <span class="kw4">struct</span> cdev SimpleDevs<span class="br0">&#91;</span>MAX_SIMPLE_DEV<span class="br0">&#93;</span>;
&nbsp;
<span class="coMULTI">/*
 * Module housekeeping.
 */</span>
<span class="kw4">static</span> <span class="kw4">int</span> simple_init<span class="br0">&#40;</span><span class="kw4">void</span><span class="br0">&#41;</span>
<span class="br0">&#123;</span>
	<span class="kw4">int</span> result;
	dev_t dev = MKDEV<span class="br0">&#40;</span>simple_major, <span class="nu0">0</span><span class="br0">&#41;</span>;
&nbsp;
	<span class="coMULTI">/* Figure out our device number. */</span>
	<span class="kw1">if</span> <span class="br0">&#40;</span>simple_major<span class="br0">&#41;</span>
		result = register_chrdev_region<span class="br0">&#40;</span>dev, <span class="nu0">2</span>, <span class="st0">"simple"</span><span class="br0">&#41;</span>;
	<span class="kw1">else</span> <span class="br0">&#123;</span>
		result = alloc_chrdev_region<span class="br0">&#40;</span>&amp;dev, <span class="nu0">0</span>, <span class="nu0">2</span>, <span class="st0">"simple"</span><span class="br0">&#41;</span>;
		simple_major = MAJOR<span class="br0">&#40;</span>dev<span class="br0">&#41;</span>;
	<span class="br0">&#125;</span>
	<span class="kw1">if</span> <span class="br0">&#40;</span>result &lt; <span class="nu0">0</span><span class="br0">&#41;</span> <span class="br0">&#123;</span>
		printk<span class="br0">&#40;</span>KERN_WARNING <span class="st0">"simple: unable to get major %d<span class="es0">\n</span>"</span>, simple_major<span class="br0">&#41;</span>;
		<span class="kw1">return</span> result;
	<span class="br0">&#125;</span>
	<span class="kw1">if</span> <span class="br0">&#40;</span>simple_major == <span class="nu0">0</span><span class="br0">&#41;</span>
		simple_major = result;
&nbsp;
	<span class="coMULTI">/* Now set up two cdevs. */</span>
	simple_setup_cdev<span class="br0">&#40;</span>SimpleDevs, <span class="nu0">0</span>, &amp;simple_remap_ops<span class="br0">&#41;</span>;
	<span class="kw1">return</span> <span class="nu0">0</span>;
<span class="br0">&#125;</span>
&nbsp;
&nbsp;
<span class="kw4">static</span> <span class="kw4">void</span> simple_cleanup<span class="br0">&#40;</span><span class="kw4">void</span><span class="br0">&#41;</span>
<span class="br0">&#123;</span>
	cdev_del<span class="br0">&#40;</span>SimpleDevs<span class="br0">&#41;</span>;
	unregister_chrdev_region<span class="br0">&#40;</span>MKDEV<span class="br0">&#40;</span>simple_major, <span class="nu0">0</span><span class="br0">&#41;</span>, <span class="nu0">2</span><span class="br0">&#41;</span>;
<span class="br0">&#125;</span>
&nbsp;
&nbsp;
module_init<span class="br0">&#40;</span>simple_init<span class="br0">&#41;</span>;
module_exit<span class="br0">&#40;</span>simple_cleanup<span class="br0">&#41;</span>;</pre>
<p>
 And use &ldquo;mknod simple c 254 0&rdquo; to create the &ldquo;/dev/simple&rdquo; device for applications to open. 
</p>

</div>

<h4><a name="mmap_user_code" id="mmap_user_code">MMAP User code</a></h4>
<div class="level4">

<p>
 A typical user code example is shown
</p>

<p>
The pointer returned by the <strong>mmap</strong> function can be used as normal read / write memory   
</p>
<pre class="code c">                <span class="co1">// bfin-uclinux-gcc -Wl,-elf2flt -o test_simple test_simple.c</span>
<span class="co2">#include &lt;fcntl.h&gt;</span>
<span class="co2">#include &lt;unistd.h&gt;</span>
<span class="co2">#include &lt;sys/types.h&gt;</span>
<span class="co2">#include &lt;sys/mman.h&gt;</span>
&nbsp;
<span class="co2">#define SIMPLE_DEVICE &quot;/dev/simple&quot;</span>
&nbsp;
<span class="kw4">int</span> main<span class="br0">&#40;</span><span class="br0">&#41;</span> <span class="br0">&#123;</span>
	<span class="kw4">int</span> i;  <span class="kw4">int</span> fd;  <span class="kw4">char</span> * p;
	fd = open<span class="br0">&#40;</span>SIMPLE_DEVICE,O_RDWR<span class="br0">&#41;</span>;
	<span class="kw1">if</span> <span class="br0">&#40;</span> fd &lt; <span class="nu0">0</span> <span class="br0">&#41;</span> <span class="br0">&#123;</span>
		<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">&#40;</span><span class="st0">"error in device <span class="es0">\n</span>"</span><span class="br0">&#41;</span>;
		exit<span class="br0">&#40;</span><span class="nu0">1</span><span class="br0">&#41;</span>;
	<span class="br0">&#125;</span>
	p = <span class="br0">&#40;</span> <span class="kw4">char</span> *<span class="br0">&#41;</span> mmap<span class="br0">&#40;</span><span class="kw2">NULL</span>, <span class="nu0">1024</span>, PROT_READ,
			   MAP_PRIVATE,fd,0x1000<span class="br0">&#41;</span>;
	<span class="kw1">if</span> <span class="br0">&#40;</span> p == MAP_FAILED <span class="br0">&#41;</span> <span class="br0">&#123;</span>
		<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">&#40;</span><span class="st0">" failed to mmap device <span class="es0">\n</span>"</span><span class="br0">&#41;</span>;
		exit<span class="br0">&#40;</span><span class="nu0">1</span><span class="br0">&#41;</span>;
	<span class="br0">&#125;</span>
	<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">&#40;</span><span class="st0">" mmap device ok p = %p<span class="es0">\n</span>"</span>,p<span class="br0">&#41;</span>;
	<span class="kw1">for</span> <span class="br0">&#40;</span>i = <span class="nu0">0</span>; i &lt; <span class="nu0">1024</span>; i++<span class="br0">&#41;</span>
		*<span class="br0">&#40;</span>p + i<span class="br0">&#41;</span> = 0x55;
&nbsp;
	<span class="kw1">for</span> <span class="br0">&#40;</span>i = <span class="nu0">0</span>; i &lt; <span class="nu0">1024</span>; i++<span class="br0">&#41;</span> <span class="br0">&#123;</span>
		<span class="kw1">if</span> <span class="br0">&#40;</span>*<span class="br0">&#40;</span>p + i<span class="br0">&#41;</span> != 0x55<span class="br0">&#41;</span> <span class="br0">&#123;</span>
			<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">&#40;</span><span class="st0">" memory write/read error! <span class="es0">\n</span>"</span><span class="br0">&#41;</span>;
			<span class="kw1">return</span> <span class="nu0">-1</span>;
		<span class="br0">&#125;</span>
	<span class="br0">&#125;</span>
	<a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">&#40;</span><span class="st0">" memory write/read succeed<span class="es0">\n</span>"</span><span class="br0">&#41;</span>;
	close<span class="br0">&#40;</span>fd<span class="br0">&#41;</span>;
	<span class="kw1">return</span> <span class="nu0">0</span>;
<span class="br0">&#125;</span></pre>
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