- Switch to inline member docs for dma_fence_ops.
- Mild polish all around.
- hyperlink all the things!
v2: - Remove the various [in] annotations, they seem really uncommon
in kerneldoc and look funny.
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: linux-media@xxxxxxxxxxxxxxx
Cc: linaro-mm-sig@xxxxxxxxxxxxxxxx
---
include/linux/dma-fence.h | 235 +++++++++++++++++++++++++-------------
1 file changed, 154 insertions(+), 81 deletions(-)
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 4c008170fe65..9d6f39bf2111 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -94,11 +94,11 @@ typedef void (*dma_fence_func_t)(struct dma_fence *fence,
struct dma_fence_cb *cb);
/**
- * struct dma_fence_cb - callback for dma_fence_add_callback
- * @node: used by dma_fence_add_callback to append this struct to fence::cb_list
+ * struct dma_fence_cb - callback for dma_fence_add_callback()
+ * @node: used by dma_fence_add_callback() to append this struct to fence::cb_list
* @func: dma_fence_func_t to call
*
- * This struct will be initialized by dma_fence_add_callback, additional
+ * This struct will be initialized by dma_fence_add_callback(), additional
* data can be passed along by embedding dma_fence_cb in another struct.
*/
struct dma_fence_cb {
@@ -108,75 +108,142 @@ struct dma_fence_cb {
/**
* struct dma_fence_ops - operations implemented for fence
- * @get_driver_name: returns the driver name.
- * @get_timeline_name: return the name of the context this fence belongs to.
- * @enable_signaling: enable software signaling of fence.
- * @signaled: [optional] peek whether the fence is signaled, can be null.
- * @wait: custom wait implementation, or dma_fence_default_wait.
- * @release: [optional] called on destruction of fence, can be null
- * @fill_driver_data: [optional] callback to fill in free-form debug info
- * Returns amount of bytes filled, or -errno.
- * @fence_value_str: [optional] fills in the value of the fence as a string
- * @timeline_value_str: [optional] fills in the current value of the timeline
- * as a string
*
- * 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 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 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->error may be set in enable_signaling, but only when false is
- * returned.
- *
- * Calling dma_fence_signal before enable_signaling is called allows
- * for a tiny race window in which enable_signaling is called during,
- * before, or after dma_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 dma_fence_signal will still be called twice, but
- * the second time will be a noop since it was already signaled.
- *
- * Notes on signaled:
- * May set fence->error if returning true.
- *
- * Notes on wait:
- * Must not be NULL, set to dma_fence_default_wait for default implementation.
- * the dma_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.
- *
- * 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.
*/
-
struct dma_fence_ops {
+ /**
+ * @get_driver_name:
+ *
+ * Returns the driver name. This is a callback to allow drivers to
+ * compute the name at runtime, without having it to store permanently
+ * for each fence, or build a cache of some sort.
+ *
+ * This callback is mandatory.
+ */
const char * (*get_driver_name)(struct dma_fence *fence);
+
+ /**
+ * @get_timeline_name:
+ *
+ * Return the name of the context this fence belongs to. This is a
+ * callback to allow drivers to compute the name at runtime, without
+ * having it to store permanently for each fence, or build a cache of
+ * some sort.
+ *
+ * This callback is mandatory.
+ */
const char * (*get_timeline_name)(struct dma_fence *fence);
+
+ /**
+ * @enable_signaling:
+ *
+ * Enable software signaling of fence.
+ *
+ * For fence implementations that have the capability for hw->hw
+ * signaling, they can implement this op to enable the necessary
+ * interrupts, or insert commands into cmdstream, etc, to avoid these
+ * costly operations for the common case where only hw->hw
+ * synchronization is required. This is called in the first
+ * dma_fence_wait() or dma_fence_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 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.
+ *
+ * &dma_fence.error may be set in enable_signaling, but only when false
+ * is returned.
+ *
+ * Since many implementations can call dma_fence_signal() even when before
+ * @enable_signaling has been called there's a race window, where the
+ * dma_fence_signal() might result in the final fence reference being
+ * released and its memory freed. To avoid this, implementations of this
+ * callback should grab their own reference using dma_fence_get(), to be
+ * released when the fence is signalled (through e.g. the interrupt
+ * handler).
+ *
+ * This callback is mandatory.
+ */
bool (*enable_signaling)(struct dma_fence *fence);
+
+ /**
+ * @signaled:
+ *
+ * Peek whether the fence is signaled, as a fastpath optimization for
+ * e.g. dma_fence_wait() or dma_fence_add_callback(). Note that this
+ * callback does not need to make any guarantees beyond that a fence
+ * once indicates as signalled must always return true from this
+ * callback. This callback may return false even if the fence has
+ * completed already, in this case information hasn't propogated throug
+ * the system yet. See also dma_fence_is_signaled().
+ *
+ * May set &dma_fence.error if returning true.
+ *
+ * This callback is optional.
+ */
bool (*signaled)(struct dma_fence *fence);
+
+ /**
+ * @wait:
+ *
+ * Custom wait implementation, or dma_fence_default_wait.
+ *
+ * Must not be NULL, set to dma_fence_default_wait for default implementation.
+ * the dma_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.
+ *
+ * This callback is mandatory.
+ */
signed long (*wait)(struct dma_fence *fence,
bool intr, signed long timeout);
+
+ /**
+ * @release:
+ *
+ * Called on destruction of fence to release additional resources.
+ * Can be called from irq context. This callback is optional. If it is
+ * NULL, then dma_fence_free() is instead called as the default
+ * implementation.
+ */
void (*release)(struct dma_fence *fence);
+ /**
+ * @fill_driver_data:
+ *
+ * Callback to fill in free-form debug info Returns amount of bytes
+ * filled, or negative error on failure.
+ *
+ * This callback is optional.
+ */
int (*fill_driver_data)(struct dma_fence *fence, void *data, int size);
+
+ /**
+ * @fence_value_str:
+ *
+ * Callback to fill in free-form debug info specific to this fence, like
+ * the sequence number.
+ *
+ * This callback is optional.
+ */
void (*fence_value_str)(struct dma_fence *fence, char *str, int size);
+
+ /**
+ * @timeline_value_str:
+ *
+ * Fills in the current value of the timeline as a string, like the
+ * sequence number. This should match what @fill_driver_data prints for
+ * the most recently signalled fence (assuming no delayed signalling).
+ */
void (*timeline_value_str)(struct dma_fence *fence,
char *str, int size);
};
@@ -189,7 +256,7 @@ void dma_fence_free(struct dma_fence *fence);
/**
* dma_fence_put - decreases refcount of the fence
- * @fence: [in] fence to reduce refcount of
+ * @fence: fence to reduce refcount of
*/
static inline void dma_fence_put(struct dma_fence *fence)
{
@@ -199,7 +266,7 @@ static inline void dma_fence_put(struct dma_fence *fence)
/**
* dma_fence_get - increases refcount of the fence
- * @fence: [in] fence to increase refcount of
+ * @fence: fence to increase refcount of
*
* Returns the same fence, with refcount increased by 1.
*/
@@ -213,7 +280,7 @@ static inline struct dma_fence *dma_fence_get(struct dma_fence *fence)
/**
* dma_fence_get_rcu - get a fence from a reservation_object_list with
* rcu read lock
- * @fence: [in] fence to increase refcount of
+ * @fence: fence to increase refcount of
*
* Function returns NULL if no refcount could be obtained, or the fence.
*/
@@ -227,7 +294,7 @@ static inline struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence)
/**
* dma_fence_get_rcu_safe - acquire a reference to an RCU tracked fence
- * @fencep: [in] pointer to fence to increase refcount of
+ * @fencep: pointer to fence to increase refcount of
*
* Function returns NULL if no refcount could be obtained, or the fence.
* This function handles acquiring a reference to a fence that may be
@@ -289,14 +356,16 @@ void dma_fence_enable_sw_signaling(struct dma_fence *fence);
/**
* dma_fence_is_signaled_locked - Return an indication if the fence
* is signaled yet.
- * @fence: [in] the fence to check
+ * @fence: the fence to check
*
* Returns true if the fence was already signaled, false if not. Since this
* function doesn't enable signaling, it is not guaranteed to ever return
- * true if dma_fence_add_callback, dma_fence_wait or
- * dma_fence_enable_sw_signaling haven't been called before.
+ * true if dma_fence_add_callback(), dma_fence_wait() or
+ * dma_fence_enable_sw_signaling() haven't been called before.
*
- * This function requires fence->lock to be held.
+ * This function requires &dma_fence.lock to be held.
+ *
+ * See also dma_fence_is_signaled().
*/
static inline bool
dma_fence_is_signaled_locked(struct dma_fence *fence)
@@ -314,17 +383,19 @@ dma_fence_is_signaled_locked(struct dma_fence *fence)
/**
* dma_fence_is_signaled - Return an indication if the fence is signaled yet.
- * @fence: [in] the fence to check
+ * @fence: the fence to check
*
* Returns true if the fence was already signaled, false if not. Since this
* function doesn't enable signaling, it is not guaranteed to ever return
- * true if dma_fence_add_callback, dma_fence_wait or
- * dma_fence_enable_sw_signaling haven't been called before.
+ * true if dma_fence_add_callback(), dma_fence_wait() or
+ * dma_fence_enable_sw_signaling() haven't been called before.
*
* It's recommended for seqno fences to call dma_fence_signal when the
* operation is complete, it makes it possible to prevent issues from
* wraparound between time of issue and time of use by checking the return
* value of this function before calling hardware-specific wait instructions.
+ *
+ * See also dma_fence_is_signaled_locked().
*/
static inline bool
dma_fence_is_signaled(struct dma_fence *fence)
@@ -342,8 +413,8 @@ dma_fence_is_signaled(struct dma_fence *fence)
/**
* __dma_fence_is_later - return if f1 is chronologically later than f2
- * @f1: [in] the first fence's seqno
- * @f2: [in] the second fence's seqno from the same context
+ * @f1: the first fence's seqno
+ * @f2: the second fence's seqno from the same context
*
* Returns true if f1 is chronologically later than f2. Both fences must be
* from the same context, since a seqno is not common across contexts.
@@ -355,8 +426,8 @@ static inline bool __dma_fence_is_later(u32 f1, u32 f2)
/**
* dma_fence_is_later - return if f1 is chronologically later than f2
- * @f1: [in] the first fence from the same context
- * @f2: [in] the second fence from the same context
+ * @f1: the first fence from the same context
+ * @f2: the second fence from the same context
*
* Returns true if f1 is chronologically later than f2. Both fences must be
* from the same context, since a seqno is not re-used across contexts.
@@ -372,8 +443,8 @@ static inline bool dma_fence_is_later(struct dma_fence *f1,
/**
* dma_fence_later - return the chronologically later fence
- * @f1: [in] the first fence from the same context
- * @f2: [in] the second fence from the same context
+ * @f1: the first fence from the same context
+ * @f2: the second fence from the same context
*
* Returns NULL if both fences are signaled, otherwise the fence that would be
* signaled last. Both fences must be from the same context, since a seqno is
@@ -398,7 +469,7 @@ static inline struct dma_fence *dma_fence_later(struct dma_fence *f1,
/**
* dma_fence_get_status_locked - returns the status upon completion
- * @fence: [in] the dma_fence to query
+ * @fence: the dma_fence to query
*
* Drivers can supply an optional error status condition before they signal
* the fence (to indicate whether the fence was completed due to an error
@@ -422,8 +493,8 @@ int dma_fence_get_status(struct dma_fence *fence);
/**
* dma_fence_set_error - flag an error condition on the fence
- * @fence: [in] the dma_fence
- * @error: [in] the error to store
+ * @fence: the dma_fence
+ * @error: the error to store
*
* Drivers can supply an optional error status condition before they signal
* the fence, to indicate that the fence was completed due to an error
@@ -449,8 +520,8 @@ signed long dma_fence_wait_any_timeout(struct dma_fence **fences,
/**
* dma_fence_wait - sleep until the fence gets signaled
- * @fence: [in] the fence to wait on
- * @intr: [in] if true, do an interruptible wait
+ * @fence: the fence to wait on
+ * @intr: if true, do an interruptible wait
*
* This function will return -ERESTARTSYS if interrupted by a signal,
* or 0 if the fence was signaled. Other error values may be
@@ -459,6 +530,8 @@ signed long dma_fence_wait_any_timeout(struct dma_fence **fences,
* Performs a synchronous wait on this fence. It is assumed the caller
* directly or indirectly holds a reference to the fence, otherwise the
* fence might be freed before return, resulting in undefined behavior.
+ *
+ * See also dma_fence_wait_timeout() and dma_fence_wait_any_timeout().
*/
static inline signed long dma_fence_wait(struct dma_fence *fence, bool intr)
{
--
2.17.0
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