USB_AUTOPM_GET_INTER(9) USB Core APIs USB_AUTOPM_GET_INTER(9)NAMEusb_autopm_get_interface - increment a USB interface´s PM-usage counter
SYNOPSIS
int usb_autopm_get_interface(struct usb_interface * intf);
ARGUMENTS
intf
the usb_interface whose counter should be incremented
DESCRIPTION
This routine should be called by an interface driver when it wants to
use intf and needs to guarantee that it is not suspended. In addition,
the routine prevents intf from being autosuspended subsequently. (Note
that this will not prevent suspend events originating in the PM core.)
This prevention will persist until usb_autopm_put_interface is called
or intf is unbound. A typical example would be a character-device
driver when its device file is opened.
The routine increments intf´s usage counter. (However if the autoresume
fails then the counter is re-decremented.) So long as the counter is
greater than 0, autosuspend will not be allowed for intf or its
usb_device. When the driver is finished using intf it should call
usb_autopm_put_interface to decrement the usage counter and queue a
delayed autosuspend request (if the counter is <= 0).
Note that intf->pm_usage_cnt is owned by the interface driver. The core
will not change its value other than the increment and decrement in
usb_autopm_get_interface and usb_autopm_put_interface. The driver may
use this simple counter-oriented discipline or may set the value any
way it likes.
Resume method calls generated by this routine can arrive at any time
while intf is suspended. They are not protected by the usb_device´s
lock but only by its pm_mutex. Drivers must provide their own
synchronization.
This routine can run only in process context.
COPYRIGHTKernel Hackers Manual 2.6. November 2013 USB_AUTOPM_GET_INTER(9)
