1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>Things to know about uio_pci_generic</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="The Userspace I/O HOWTO"><link rel="up" href="uio_pci_generic.html" title="Chapter&#160;5.&#160;Generic PCI UIO driver"><link rel="prev" href="uio_pci_generic.html" title="Chapter&#160;5.&#160;Generic PCI UIO driver"><link rel="next" href="uio_pci_generic_userspace.html" title="Writing userspace driver using uio_pci_generic"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Things to know about uio_pci_generic</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="uio_pci_generic.html">Prev</a>&#160;</td><th width="60%" align="center">Chapter&#160;5.&#160;Generic PCI UIO driver</th><td width="20%" align="right">&#160;<a accesskey="n" href="uio_pci_generic_userspace.html">Next</a></td></tr></table><hr></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="uio_pci_generic_internals"></a>Things to know about uio_pci_generic</h2></div></div></div><p>
2Interrupts are handled using the Interrupt Disable bit in the PCI command
3register and Interrupt Status bit in the PCI status register.  All devices
4compliant to PCI 2.3 (circa 2002) and all compliant PCI Express devices should
5support these bits.  uio_pci_generic detects this support, and won't bind to
6devices which do not support the Interrupt Disable Bit in the command register.
7	</p><p>
8On each interrupt, uio_pci_generic sets the Interrupt Disable bit.
9This prevents the device from generating further interrupts
10until the bit is cleared. The userspace driver should clear this
11bit before blocking and waiting for more interrupts.
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