'\" t
.\"     Title: struct fence_ops
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: Device drivers infrastructure
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "STRUCT FENCE_OPS" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "Device drivers infrastructure"
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.SH "NAME"
struct_fence_ops \- operations implemented for fence
.SH "SYNOPSIS"
.sp
.nf
struct fence_ops {
  const char * (* get_driver_name) (struct fence *fence);
  const char * (* get_timeline_name) (struct fence *fence);
  bool (* enable_signaling) (struct fence *fence);
  bool (* signaled) (struct fence *fence);
  signed long (* wait) (struct fence *fence, bool intr, signed long timeout);
  void (* release) (struct fence *fence);
  int (* fill_driver_data) (struct fence *fence, void *data, int size);
  void (* fence_value_str) (struct fence *fence, char *str, int size);
  void (* timeline_value_str) (struct fence *fence, char *str, int size);
};  
.fi
.SH "MEMBERS"
.PP
get_driver_name
.RS 4
returns the driver name\&.
.RE
.PP
get_timeline_name
.RS 4
return the name of the context this fence belongs to\&.
.RE
.PP
enable_signaling
.RS 4
enable software signaling of fence\&.
.RE
.PP
signaled
.RS 4
[optional] peek whether the fence is signaled, can be null\&.
.RE
.PP
wait
.RS 4
custom wait implementation, or fence_default_wait\&.
.RE
.PP
release
.RS 4
[optional] called on destruction of fence, can be null
.RE
.PP
fill_driver_data
.RS 4
[optional] callback to fill in free\-form debug info Returns amount of bytes filled, or \-errno\&.
.RE
.PP
fence_value_str
.RS 4
[optional] fills in the value of the fence as a string
.RE
.PP
timeline_value_str
.RS 4
[optional] fills in the current value of the timeline as a string
.RE
.SH "DESCRIPTION"
.PP
Notes on enable_signaling: For fence implementations that have the capability for hw\->hw signaling, they can implement this op to enable the necessary irqs, or insert commands into cmdstream, etc\&. This is called in the first
\fBwait\fR
or
\fBadd_callback\fR
path to let the fence implementation know that there is another driver waiting on the signal (ie\&. hw\->sw case)\&.
.PP
This function can be called called from atomic context, but not from irq context, so normal spinlocks can be used\&.
.PP
A return value of false indicates the fence already passed, or some failure occurred that made it impossible to enable signaling\&. True indicates successful enabling\&.
.PP
fence\->status may be set in enable_signaling, but only when false is returned\&.
.PP
Calling fence_signal before enable_signaling is called allows for a tiny race window in which enable_signaling is called during, before, or after fence_signal\&. To fight this, it is recommended that before enable_signaling returns true an extra reference is taken on the fence, to be released when the fence is signaled\&. This will mean fence_signal will still be called twice, but the second time will be a noop since it was already signaled\&.
.PP
Notes on signaled: May set fence\->status if returning true\&.
.PP
Notes on wait: Must not be NULL, set to fence_default_wait for default implementation\&. the fence_default_wait implementation should work for any fence, as long as enable_signaling works correctly\&.
.PP
Must return \-ERESTARTSYS if the wait is intr = true and the wait was interrupted, and remaining jiffies if fence has signaled, or 0 if wait timed out\&. Can also return other error values on custom implementations, which should be treated as if the fence is signaled\&. For example a hardware lockup could be reported like that\&.
.PP
Notes on release: Can be NULL, this function allows additional commands to run on destruction of the fence\&. Can be called from irq context\&. If pointer is set to NULL, kfree will get called instead\&.
.SH "COPYRIGHT"
.br