struct fence_ops — operations implemented for fence
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);
}; returns the driver name.
return the name of the context this fence belongs to.
enable software signaling of fence.
[optional] peek whether the fence is signaled, can be null.
custom wait implementation, or fence_default_wait.
[optional] called on destruction of fence, can be null
[optional] callback to fill in free-form debug info Returns amount of bytes filled, or -errno.
[optional] fills in the value of the fence as a string
[optional] fills in the current value of the timeline as a string
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 wait or add_callback path to let the fence
implementation know that there is another driver waiting on
the signal (ie. hw->sw case).
This function can be called called from atomic context, but not from irq context, so normal spinlocks can be used.
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.
fence->status may be set in enable_signaling, but only when false is returned.
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.
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.
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.