Linux Certif

Toute la documentation sur la certification Linux LPI

usb_autopm_get_interface

NAME

usb_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.

COPYRIGHT