struct usb_interface(9)
NAME
struct_usb_interface - what usb device drivers talk to
SYNOPSIS
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 needs_remote_wakeup:1;
struct device dev;
struct device * usb_dev;
int pm_usage_cnt;
};
MEMBERS
- altsetting
- 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. - cur_altsetting
- the current altsetting.
- num_altsetting
- number of altsettings defined.
- intf_assoc
- interface association descriptor
- minor
- 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 probe function of the driver, after it has been assigned a minor number from the USB core by calling
usb_register_dev. - condition
- binding state of the interface: not bound, binding (in probe), bound to a driver, or unbinding (in disconnect)
- is_active
- flag set when the interface is bound and not suspended.
- sysfs_files_created
- sysfs attributes exist
- needs_remote_wakeup
- flag set when the driver requires remote-wakeup capability during
autosuspend. - dev
- driver model´s view of this device
- usb_dev
- if an interface is bound to the USB major, this will point to the
sysfs representation for that device. - pm_usage_cnt
- PM usage counter for this interface; autosuspend is not allowed
unless the counter is 0.
DESCRIPTION
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 "class" 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.
The driver that is bound to the interface can use standard driver model calls such as dev_get_drvdata on the dev member of this structure.
Each interface may have alternate settings. The initial configuration
of a device sets altsetting 0, but the device driver can change that
setting using usb_set_interface. 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.
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 usb_altnum_to_altsetting to look
up an alternate setting in the altsetting array based on its number.