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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>struct usb_interface</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="ch04.html" title="Chapter 4. Host-Side Data Types and Macros" /><link rel="prev" href="re17.html" title="struct usb_host_endpoint" /><link rel="next" href="re19.html" title="struct usb_interface_cache" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>struct usb_interface</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re17.html">Prev</a> </td><th width="60%" align="center">Chapter 4. Host-Side Data Types and Macros</th><td width="20%" align="right"> <a accesskey="n" href="re19.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="struct usb_interface"><a id="API-struct-usb-interface"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>struct usb_interface —
what usb device drivers talk to
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><pre class="programlisting">
struct usb_interface {
struct usb_host_interface * altsetting;
struct usb_host_interface * cur_altsetting;
unsigned num_altsetting;
struct usb_interface_assoc_descriptor * intf_assoc;
int minor;
enum usb_interface_condition condition;
unsigned is_active:1;
unsigned sysfs_files_created:1;
unsigned ep_devs_created:1;
unsigned unregistering:1;
unsigned needs_remote_wakeup:1;
unsigned needs_altsetting0:1;
unsigned needs_binding:1;
unsigned reset_running:1;
struct device dev;
struct device * usb_dev;
atomic_t pm_usage_cnt;
struct work_struct reset_ws;
}; </pre></div><div class="refsect1" title="Members"><a id="id3101892"></a><h2>Members</h2><div class="variablelist"><dl><dt><span class="term">altsetting</span></dt><dd><p>
array of interface structures, one for each alternate
setting that may be selected. Each one includes a set of
endpoint configurations. They will be in no particular order.
</p></dd><dt><span class="term">cur_altsetting</span></dt><dd><p>
the current altsetting.
</p></dd><dt><span class="term">num_altsetting</span></dt><dd><p>
number of altsettings defined.
</p></dd><dt><span class="term">intf_assoc</span></dt><dd><p>
interface association descriptor
</p></dd><dt><span class="term">minor</span></dt><dd><p>
the minor number assigned to this interface, if this
interface is bound to a driver that uses the USB major number.
If this interface does not use the USB major, this field should
be unused. The driver should set this value in the <code class="function">probe</code>
function of the driver, after it has been assigned a minor
number from the USB core by calling <code class="function">usb_register_dev</code>.
</p></dd><dt><span class="term">condition</span></dt><dd><p>
binding state of the interface: not bound, binding
(in <code class="function">probe</code>), bound to a driver, or unbinding (in <code class="function">disconnect</code>)
</p></dd><dt><span class="term">is_active</span></dt><dd><p>
flag set when the interface is bound and not suspended.
</p></dd><dt><span class="term">sysfs_files_created</span></dt><dd><p>
sysfs attributes exist
</p></dd><dt><span class="term">ep_devs_created</span></dt><dd><p>
endpoint child pseudo-devices exist
</p></dd><dt><span class="term">unregistering</span></dt><dd><p>
flag set when the interface is being unregistered
</p></dd><dt><span class="term">needs_remote_wakeup</span></dt><dd><p>
flag set when the driver requires remote-wakeup
capability during autosuspend.
</p></dd><dt><span class="term">needs_altsetting0</span></dt><dd><p>
flag set when a set-interface request for altsetting 0
has been deferred.
</p></dd><dt><span class="term">needs_binding</span></dt><dd><p>
flag set when the driver should be re-probed or unbound
following a reset or suspend operation it doesn't support.
</p></dd><dt><span class="term">reset_running</span></dt><dd><p>
set to 1 if the interface is currently running a
queued reset so that <code class="function">usb_cancel_queued_reset</code> doesn't try to
remove from the workqueue when running inside the worker
thread. See <code class="function">__usb_queue_reset_device</code>.
</p></dd><dt><span class="term">dev</span></dt><dd><p>
driver model's view of this device
</p></dd><dt><span class="term">usb_dev</span></dt><dd><p>
if an interface is bound to the USB major, this will point
to the sysfs representation for that device.
</p></dd><dt><span class="term">pm_usage_cnt</span></dt><dd><p>
PM usage counter for this interface; autosuspend is not
allowed unless the counter is 0.
</p></dd><dt><span class="term">reset_ws</span></dt><dd><p>
Used for scheduling resets from atomic context.
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id3102157"></a><h2>Description</h2><p>
USB device drivers attach to interfaces on a physical device. Each
interface encapsulates a single high level function, such as feeding
an audio stream to a speaker or reporting a change in a volume control.
Many USB devices only have one interface. The protocol used to talk to
an interface's endpoints can be defined in a usb <span class="quote">“<span class="quote">class</span>”</span> specification,
or by a product's vendor. The (default) control endpoint is part of
every interface, but is never listed among the interface's descriptors.
</p><p>
The driver that is bound to the interface can use standard driver model
calls such as <code class="function">dev_get_drvdata</code> on the dev member of this structure.
</p><p>
Each interface may have alternate settings. The initial configuration
of a device sets altsetting 0, but the device driver can change
that setting using <code class="function">usb_set_interface</code>. Alternate settings are often
used to control the use of periodic endpoints, such as by having
different endpoints use different amounts of reserved USB bandwidth.
All standards-conformant USB devices that use isochronous endpoints
will use them in non-default settings.
</p><p>
The USB specification says that alternate setting numbers must run from
0 to one less than the total number of alternate settings. But some
devices manage to mess this up, and the structures aren't necessarily
stored in numerical order anyhow. Use <code class="function">usb_altnum_to_altsetting</code> to
look up an alternate setting in the altsetting array based on its number.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re17.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch04.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re19.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>struct usb_host_endpoint</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>struct usb_interface_cache</span></td></tr></table></div></body></html>
