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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>usb_set_device_state</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="The Linux-USB Host Side API" /><link rel="up" href="ch05.html" title="Chapter 5. USB Core APIs" /><link rel="prev" href="re106.html" title="usb_hub_clear_tt_buffer" /><link rel="next" href="re108.html" title="usb_root_hub_lost_power" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>usb_set_device_state</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re106.html">Prev</a> </td><th width="60%" align="center">Chapter 5. USB Core APIs</th><td width="20%" align="right"> <a accesskey="n" href="re108.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="usb_set_device_state"><a id="API-usb-set-device-state"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>usb_set_device_state —
change a device's current state (usbcore, hcds)
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">usb_set_device_state </b>(</code></td><td>struct usb_device * <var class="pdparam">udev</var>, </td></tr><tr><td> </td><td>enum usb_device_state <var class="pdparam">new_state</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id3118256"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>udev</code></em></span></dt><dd><p>
pointer to device whose state should be changed
</p></dd><dt><span class="term"><em class="parameter"><code>new_state</code></em></span></dt><dd><p>
new state value to be stored
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id3118301"></a><h2>Description</h2><p>
udev->state is _not_ fully protected by the device lock. Although
most transitions are made only while holding the lock, the state can
can change to USB_STATE_NOTATTACHED at almost any time. This
is so that devices can be marked as disconnected as soon as possible,
without having to wait for any semaphores to be released. As a result,
all changes to any device's state must be protected by the
device_state_lock spinlock.
</p><p>
Once a device has been added to the device tree, all changes to its state
should be made using this routine. The state should _not_ be set directly.
</p><p>
If udev->state is already USB_STATE_NOTATTACHED then no change is made.
Otherwise udev->state is set to new_state, and if new_state is
USB_STATE_NOTATTACHED then all of udev's descendants' states are also set
to USB_STATE_NOTATTACHED.
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