<?xml version="1.0" encoding="ANSI_X3.4-1968" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>Using uio_pdrv_genirq for platform devices</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="The Userspace I/O HOWTO" /><link rel="up" href="custom_kernel_module.html" title="Chapter 3. Writing your own kernel module" /><link rel="prev" href="ch03s03.html" title="Using uio_pdrv for platform devices" /><link rel="next" href="userspace_driver.html" title="Chapter 4. Writing a driver in userspace" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Using uio_pdrv_genirq for platform devices</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch03s03.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Writing your own kernel module</th><td width="20%" align="right"> <a accesskey="n" href="userspace_driver.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Using uio_pdrv_genirq for platform devices"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="using_uio_pdrv_genirq"></a>Using uio_pdrv_genirq for platform devices</h2></div></div></div><p> Especially in embedded devices, you frequently find chips where the irq pin is tied to its own dedicated interrupt line. In such cases, where you can be really sure the interrupt is not shared, we can take the concept of <code class="varname">uio_pdrv</code> one step further and use a generic interrupt handler. That's what <code class="varname">uio_pdrv_genirq</code> does. </p><p> The setup for this driver is the same as described above for <code class="varname">uio_pdrv</code>, except that you do not implement an interrupt handler. The <code class="varname">.handler</code> element of <code class="varname">struct uio_info</code> must remain <code class="varname">NULL</code>. The <code class="varname">.irq_flags</code> element must not contain <code class="varname">IRQF_SHARED</code>. </p><p> You will set the <code class="varname">.name</code> element of <code class="varname">struct platform_device</code> to <code class="varname">"uio_pdrv_genirq"</code> to use this driver. </p><p> The generic interrupt handler of <code class="varname">uio_pdrv_genirq</code> will simply disable the interrupt line using <code class="function">disable_irq_nosync()</code>. After doing its work, userspace can reenable the interrupt by writing 0x00000001 to the UIO device file. The driver already implements an <code class="function">irq_control()</code> to make this possible, you must not implement your own. </p><p> Using <code class="varname">uio_pdrv_genirq</code> not only saves a few lines of interrupt handler code. You also do not need to know anything about the chip's internal registers to create the kernel part of the driver. All you need to know is the irq number of the pin the chip is connected to. </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch03s03.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="custom_kernel_module.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="userspace_driver.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Using uio_pdrv for platform devices </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 4. Writing a driver in userspace</td></tr></table></div></body></html>
