'\" t
.\"     Title: usb_poison_urb
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: USB Core APIs
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "USB_POISON_URB" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "USB Core APIs"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
usb_poison_urb \- reliably kill a transfer and prevent further use of an URB
.SH "SYNOPSIS"
.HP \w'void\ usb_poison_urb('u
.BI "void usb_poison_urb(struct\ urb\ *\ " "urb" ");"
.SH "ARGUMENTS"
.PP
\fIurb\fR
.RS 4
pointer to URB describing a previously submitted request, may be NULL
.RE
.SH "DESCRIPTION"
.PP
This routine cancels an in\-progress request\&. It is guaranteed that upon return all completion handlers will have finished and the URB will be totally idle and cannot be reused\&. These features make this an ideal way to stop I/O in a
\fBdisconnect\fR
callback\&. If the request has not already finished or been unlinked the completion handler will see urb\->status == \-ENOENT\&.
.PP
After and while the routine runs, attempts to resubmit the URB will fail with error \-EPERM\&. Thus even if the URB\*(Aqs completion handler always tries to resubmit, it will not succeed and the URB will become idle\&.
.PP
The URB must not be deallocated while this routine is running\&. In particular, when a driver calls this routine, it must insure that the completion handler cannot deallocate the URB\&.
.PP
This routine may not be used in an interrupt context (such as a bottom half or a completion handler), or when holding a spinlock, or in other situations where the caller can\*(Aqt
\fBschedule\fR\&.
.PP
This routine should not be called by a driver after its disconnect method has returned\&.
.SH "COPYRIGHT"
.br