| Message ID | 20180704092909.6599-6-daniel.vetter@ffwll.ch (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Am 04.07.2018 um 11:29 schrieb Daniel Vetter: > - Intro section that links to how this is exposed to userspace. > - Lots more hyperlinks. > - Minor clarifications and style polish > > v2: Add misplaced hunk of kerneldoc from a different patch. > > Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> > Cc: Sumit Semwal <sumit.semwal@linaro.org> > Cc: Gustavo Padovan <gustavo@padovan.org> > Cc: linux-media@vger.kernel.org > Cc: linaro-mm-sig@lists.linaro.org Reviewed-by: Christian König <christian.koenig@amd.com> > --- > Documentation/driver-api/dma-buf.rst | 6 ++ > drivers/dma-buf/dma-fence.c | 147 +++++++++++++++++++-------- > 2 files changed, 109 insertions(+), 44 deletions(-) > > diff --git a/Documentation/driver-api/dma-buf.rst b/Documentation/driver-api/dma-buf.rst > index dc384f2f7f34..b541e97c7ab1 100644 > --- a/Documentation/driver-api/dma-buf.rst > +++ b/Documentation/driver-api/dma-buf.rst > @@ -130,6 +130,12 @@ Reservation Objects > DMA Fences > ---------- > > +.. kernel-doc:: drivers/dma-buf/dma-fence.c > + :doc: DMA fences overview > + > +DMA Fences Functions Reference > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > .. kernel-doc:: drivers/dma-buf/dma-fence.c > :export: > > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c > index 7a92f85a4cec..1551ca7df394 100644 > --- a/drivers/dma-buf/dma-fence.c > +++ b/drivers/dma-buf/dma-fence.c > @@ -38,12 +38,43 @@ EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal); > */ > static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(0); > > +/** > + * DOC: DMA fences overview > + * > + * DMA fences, represented by &struct dma_fence, are the kernel internal > + * synchronization primitive for DMA operations like GPU rendering, video > + * encoding/decoding, or displaying buffers on a screen. > + * > + * A fence is initialized using dma_fence_init() and completed using > + * dma_fence_signal(). Fences are associated with a context, allocated through > + * dma_fence_context_alloc(), and all fences on the same context are > + * fully ordered. > + * > + * Since the purposes of fences is to facilitate cross-device and > + * cross-application synchronization, there's multiple ways to use one: > + * > + * - Individual fences can be exposed as a &sync_file, accessed as a file > + * descriptor from userspace, created by calling sync_file_create(). This is > + * called explicit fencing, since userspace passes around explicit > + * synchronization points. > + * > + * - Some subsystems also have their own explicit fencing primitives, like > + * &drm_syncobj. Compared to &sync_file, a &drm_syncobj allows the underlying > + * fence to be updated. > + * > + * - Then there's also implicit fencing, where the synchronization points are > + * implicitly passed around as part of shared &dma_buf instances. Such > + * implicit fences are stored in &struct reservation_object through the > + * &dma_buf.resv pointer. > + */ > + > /** > * dma_fence_context_alloc - allocate an array of fence contexts > - * @num: [in] amount of contexts to allocate > + * @num: amount of contexts to allocate > * > - * This function will return the first index of the number of fences allocated. > - * The fence context is used for setting fence->context to a unique number. > + * This function will return the first index of the number of fence contexts > + * allocated. The fence context is used for setting &dma_fence.context to a > + * unique number by passing the context to dma_fence_init(). > */ > u64 dma_fence_context_alloc(unsigned num) > { > @@ -59,10 +90,14 @@ EXPORT_SYMBOL(dma_fence_context_alloc); > * Signal completion for software callbacks on a fence, this will unblock > * dma_fence_wait() calls and run all the callbacks added with > * dma_fence_add_callback(). Can be called multiple times, but since a fence > - * can only go from unsignaled to signaled state, it will only be effective > - * the first time. > + * can only go from the unsignaled to the signaled state and not back, it will > + * only be effective the first time. > + * > + * Unlike dma_fence_signal(), this function must be called with &dma_fence.lock > + * held. > * > - * Unlike dma_fence_signal, this function must be called with fence->lock held. > + * Returns 0 on success and a negative error value when @fence has been > + * signalled already. > */ > int dma_fence_signal_locked(struct dma_fence *fence) > { > @@ -102,8 +137,11 @@ EXPORT_SYMBOL(dma_fence_signal_locked); > * Signal completion for software callbacks on a fence, this will unblock > * dma_fence_wait() calls and run all the callbacks added with > * dma_fence_add_callback(). Can be called multiple times, but since a fence > - * can only go from unsignaled to signaled state, it will only be effective > - * the first time. > + * can only go from the unsignaled to the signaled state and not back, it will > + * only be effective the first time. > + * > + * Returns 0 on success and a negative error value when @fence has been > + * signalled already. > */ > int dma_fence_signal(struct dma_fence *fence) > { > @@ -136,9 +174,9 @@ EXPORT_SYMBOL(dma_fence_signal); > /** > * dma_fence_wait_timeout - sleep until the fence gets signaled > * or until timeout elapses > - * @fence: [in] the fence to wait on > - * @intr: [in] if true, do an interruptible wait > - * @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT > + * @fence: the fence to wait on > + * @intr: if true, do an interruptible wait > + * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT > * > * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the > * remaining timeout in jiffies on success. Other error values may be > @@ -148,6 +186,8 @@ EXPORT_SYMBOL(dma_fence_signal); > * directly or indirectly (buf-mgr between reservation and committing) > * holds a reference to the fence, otherwise the fence might be > * freed before return, resulting in undefined behavior. > + * > + * See also dma_fence_wait() and dma_fence_wait_any_timeout(). > */ > signed long > dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout) > @@ -167,6 +207,13 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout) > } > EXPORT_SYMBOL(dma_fence_wait_timeout); > > +/** > + * dma_fence_release - default relese function for fences > + * @kref: &dma_fence.recfount > + * > + * This is the default release functions for &dma_fence. Drivers shouldn't call > + * this directly, but instead call dma_fence_put(). > + */ > void dma_fence_release(struct kref *kref) > { > struct dma_fence *fence = > @@ -184,6 +231,13 @@ void dma_fence_release(struct kref *kref) > } > EXPORT_SYMBOL(dma_fence_release); > > +/** > + * dma_fence_free - default release function for &dma_fence. > + * @fence: fence to release > + * > + * This is the default implementation for &dma_fence_ops.release. It calls > + * kfree_rcu() on @fence. > + */ > void dma_fence_free(struct dma_fence *fence) > { > kfree_rcu(fence, rcu); > @@ -192,10 +246,11 @@ EXPORT_SYMBOL(dma_fence_free); > > /** > * dma_fence_enable_sw_signaling - enable signaling on fence > - * @fence: [in] the fence to enable > + * @fence: the fence to enable > * > - * this will request for sw signaling to be enabled, to make the fence > - * complete as soon as possible > + * This will request for sw signaling to be enabled, to make the fence > + * complete as soon as possible. This calls &dma_fence_ops.enable_signaling > + * internally. > */ > void dma_fence_enable_sw_signaling(struct dma_fence *fence) > { > @@ -220,24 +275,24 @@ EXPORT_SYMBOL(dma_fence_enable_sw_signaling); > /** > * dma_fence_add_callback - add a callback to be called when the fence > * is signaled > - * @fence: [in] the fence to wait on > - * @cb: [in] the callback to register > - * @func: [in] the function to call > + * @fence: the fence to wait on > + * @cb: the callback to register > + * @func: the function to call > * > - * cb will be initialized by dma_fence_add_callback, no initialization > + * @cb will be initialized by dma_fence_add_callback(), no initialization > * by the caller is required. Any number of callbacks can be registered > * to a fence, but a callback can only be registered to one fence at a time. > * > * Note that the callback can be called from an atomic context. If > * fence is already signaled, this function will return -ENOENT (and > - * *not* call the callback) > + * *not* call the callback). > * > * Add a software callback to the fence. Same restrictions apply to > - * refcount as it does to dma_fence_wait, however the caller doesn't need to > - * keep a refcount to fence afterwards: when software access is enabled, > - * the creator of the fence is required to keep the fence alive until > - * after it signals with dma_fence_signal. The callback itself can be called > - * from irq context. > + * refcount as it does to dma_fence_wait(), however the caller doesn't need to > + * keep a refcount to fence afterward dma_fence_add_callback() has returned: > + * when software access is enabled, the creator of the fence is required to keep > + * the fence alive until after it signals with dma_fence_signal(). The callback > + * itself can be called from irq context. > * > * Returns 0 in case of success, -ENOENT if the fence is already signaled > * and -EINVAL in case of error. > @@ -286,7 +341,7 @@ EXPORT_SYMBOL(dma_fence_add_callback); > > /** > * dma_fence_get_status - returns the status upon completion > - * @fence: [in] the dma_fence to query > + * @fence: the dma_fence to query > * > * This wraps dma_fence_get_status_locked() to return the error status > * condition on a signaled fence. See dma_fence_get_status_locked() for more > @@ -311,8 +366,8 @@ EXPORT_SYMBOL(dma_fence_get_status); > > /** > * dma_fence_remove_callback - remove a callback from the signaling list > - * @fence: [in] the fence to wait on > - * @cb: [in] the callback to remove > + * @fence: the fence to wait on > + * @cb: the callback to remove > * > * Remove a previously queued callback from the fence. This function returns > * true if the callback is successfully removed, or false if the fence has > @@ -323,6 +378,9 @@ EXPORT_SYMBOL(dma_fence_get_status); > * doing, since deadlocks and race conditions could occur all too easily. For > * this reason, it should only ever be done on hardware lockup recovery, > * with a reference held to the fence. > + * > + * Behaviour is undefined if @cb has not been added to @fence using > + * dma_fence_add_callback() beforehand. > */ > bool > dma_fence_remove_callback(struct dma_fence *fence, struct dma_fence_cb *cb) > @@ -359,9 +417,9 @@ dma_fence_default_wait_cb(struct dma_fence *fence, struct dma_fence_cb *cb) > /** > * dma_fence_default_wait - default sleep until the fence gets signaled > * or until timeout elapses > - * @fence: [in] the fence to wait on > - * @intr: [in] if true, do an interruptible wait > - * @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT > + * @fence: the fence to wait on > + * @intr: if true, do an interruptible wait > + * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT > * > * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the > * remaining timeout in jiffies on success. If timeout is zero the value one is > @@ -454,12 +512,12 @@ dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count, > /** > * dma_fence_wait_any_timeout - sleep until any fence gets signaled > * or until timeout elapses > - * @fences: [in] array of fences to wait on > - * @count: [in] number of fences to wait on > - * @intr: [in] if true, do an interruptible wait > - * @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT > - * @idx: [out] the first signaled fence index, meaningful only on > - * positive return > + * @fences: array of fences to wait on > + * @count: number of fences to wait on > + * @intr: if true, do an interruptible wait > + * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT > + * @idx: used to store the first signaled fence index, meaningful only on > + * positive return > * > * Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if > * interrupted, 0 if the wait timed out, or the remaining timeout in jiffies > @@ -468,6 +526,8 @@ dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count, > * Synchronous waits for the first fence in the array to be signaled. The > * caller needs to hold a reference to all fences in the array, otherwise a > * fence might be freed before return, resulting in undefined behavior. > + * > + * See also dma_fence_wait() and dma_fence_wait_timeout(). > */ > signed long > dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count, > @@ -540,19 +600,18 @@ EXPORT_SYMBOL(dma_fence_wait_any_timeout); > > /** > * dma_fence_init - Initialize a custom fence. > - * @fence: [in] the fence to initialize > - * @ops: [in] the dma_fence_ops for operations on this fence > - * @lock: [in] the irqsafe spinlock to use for locking this fence > - * @context: [in] the execution context this fence is run on > - * @seqno: [in] a linear increasing sequence number for this context > + * @fence: the fence to initialize > + * @ops: the dma_fence_ops for operations on this fence > + * @lock: the irqsafe spinlock to use for locking this fence > + * @context: the execution context this fence is run on > + * @seqno: a linear increasing sequence number for this context > * > * Initializes an allocated fence, the caller doesn't have to keep its > * refcount after committing with this fence, but it will need to hold a > - * refcount again if dma_fence_ops.enable_signaling gets called. This can > - * be used for other implementing other types of fence. > + * refcount again if &dma_fence_ops.enable_signaling gets called. > * > * context and seqno are used for easy comparison between fences, allowing > - * to check which fence is later by simply using dma_fence_later. > + * to check which fence is later by simply using dma_fence_later(). > */ > void > dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
diff --git a/Documentation/driver-api/dma-buf.rst b/Documentation/driver-api/dma-buf.rst index dc384f2f7f34..b541e97c7ab1 100644 --- a/Documentation/driver-api/dma-buf.rst +++ b/Documentation/driver-api/dma-buf.rst @@ -130,6 +130,12 @@ Reservation Objects DMA Fences ---------- +.. kernel-doc:: drivers/dma-buf/dma-fence.c + :doc: DMA fences overview + +DMA Fences Functions Reference +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + .. kernel-doc:: drivers/dma-buf/dma-fence.c :export: diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c index 7a92f85a4cec..1551ca7df394 100644 --- a/drivers/dma-buf/dma-fence.c +++ b/drivers/dma-buf/dma-fence.c @@ -38,12 +38,43 @@ EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal); */ static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(0); +/** + * DOC: DMA fences overview + * + * DMA fences, represented by &struct dma_fence, are the kernel internal + * synchronization primitive for DMA operations like GPU rendering, video + * encoding/decoding, or displaying buffers on a screen. + * + * A fence is initialized using dma_fence_init() and completed using + * dma_fence_signal(). Fences are associated with a context, allocated through + * dma_fence_context_alloc(), and all fences on the same context are + * fully ordered. + * + * Since the purposes of fences is to facilitate cross-device and + * cross-application synchronization, there's multiple ways to use one: + * + * - Individual fences can be exposed as a &sync_file, accessed as a file + * descriptor from userspace, created by calling sync_file_create(). This is + * called explicit fencing, since userspace passes around explicit + * synchronization points. + * + * - Some subsystems also have their own explicit fencing primitives, like + * &drm_syncobj. Compared to &sync_file, a &drm_syncobj allows the underlying + * fence to be updated. + * + * - Then there's also implicit fencing, where the synchronization points are + * implicitly passed around as part of shared &dma_buf instances. Such + * implicit fences are stored in &struct reservation_object through the + * &dma_buf.resv pointer. + */ + /** * dma_fence_context_alloc - allocate an array of fence contexts - * @num: [in] amount of contexts to allocate + * @num: amount of contexts to allocate * - * This function will return the first index of the number of fences allocated. - * The fence context is used for setting fence->context to a unique number. + * This function will return the first index of the number of fence contexts + * allocated. The fence context is used for setting &dma_fence.context to a + * unique number by passing the context to dma_fence_init(). */ u64 dma_fence_context_alloc(unsigned num) { @@ -59,10 +90,14 @@ EXPORT_SYMBOL(dma_fence_context_alloc); * Signal completion for software callbacks on a fence, this will unblock * dma_fence_wait() calls and run all the callbacks added with * dma_fence_add_callback(). Can be called multiple times, but since a fence - * can only go from unsignaled to signaled state, it will only be effective - * the first time. + * can only go from the unsignaled to the signaled state and not back, it will + * only be effective the first time. + * + * Unlike dma_fence_signal(), this function must be called with &dma_fence.lock + * held. * - * Unlike dma_fence_signal, this function must be called with fence->lock held. + * Returns 0 on success and a negative error value when @fence has been + * signalled already. */ int dma_fence_signal_locked(struct dma_fence *fence) { @@ -102,8 +137,11 @@ EXPORT_SYMBOL(dma_fence_signal_locked); * Signal completion for software callbacks on a fence, this will unblock * dma_fence_wait() calls and run all the callbacks added with * dma_fence_add_callback(). Can be called multiple times, but since a fence - * can only go from unsignaled to signaled state, it will only be effective - * the first time. + * can only go from the unsignaled to the signaled state and not back, it will + * only be effective the first time. + * + * Returns 0 on success and a negative error value when @fence has been + * signalled already. */ int dma_fence_signal(struct dma_fence *fence) { @@ -136,9 +174,9 @@ EXPORT_SYMBOL(dma_fence_signal); /** * dma_fence_wait_timeout - sleep until the fence gets signaled * or until timeout elapses - * @fence: [in] the fence to wait on - * @intr: [in] if true, do an interruptible wait - * @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT + * @fence: the fence to wait on + * @intr: if true, do an interruptible wait + * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT * * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the * remaining timeout in jiffies on success. Other error values may be @@ -148,6 +186,8 @@ EXPORT_SYMBOL(dma_fence_signal); * directly or indirectly (buf-mgr between reservation and committing) * holds a reference to the fence, otherwise the fence might be * freed before return, resulting in undefined behavior. + * + * See also dma_fence_wait() and dma_fence_wait_any_timeout(). */ signed long dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout) @@ -167,6 +207,13 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout) } EXPORT_SYMBOL(dma_fence_wait_timeout); +/** + * dma_fence_release - default relese function for fences + * @kref: &dma_fence.recfount + * + * This is the default release functions for &dma_fence. Drivers shouldn't call + * this directly, but instead call dma_fence_put(). + */ void dma_fence_release(struct kref *kref) { struct dma_fence *fence = @@ -184,6 +231,13 @@ void dma_fence_release(struct kref *kref) } EXPORT_SYMBOL(dma_fence_release); +/** + * dma_fence_free - default release function for &dma_fence. + * @fence: fence to release + * + * This is the default implementation for &dma_fence_ops.release. It calls + * kfree_rcu() on @fence. + */ void dma_fence_free(struct dma_fence *fence) { kfree_rcu(fence, rcu); @@ -192,10 +246,11 @@ EXPORT_SYMBOL(dma_fence_free); /** * dma_fence_enable_sw_signaling - enable signaling on fence - * @fence: [in] the fence to enable + * @fence: the fence to enable * - * this will request for sw signaling to be enabled, to make the fence - * complete as soon as possible + * This will request for sw signaling to be enabled, to make the fence + * complete as soon as possible. This calls &dma_fence_ops.enable_signaling + * internally. */ void dma_fence_enable_sw_signaling(struct dma_fence *fence) { @@ -220,24 +275,24 @@ EXPORT_SYMBOL(dma_fence_enable_sw_signaling); /** * dma_fence_add_callback - add a callback to be called when the fence * is signaled - * @fence: [in] the fence to wait on - * @cb: [in] the callback to register - * @func: [in] the function to call + * @fence: the fence to wait on + * @cb: the callback to register + * @func: the function to call * - * cb will be initialized by dma_fence_add_callback, no initialization + * @cb will be initialized by dma_fence_add_callback(), no initialization * by the caller is required. Any number of callbacks can be registered * to a fence, but a callback can only be registered to one fence at a time. * * Note that the callback can be called from an atomic context. If * fence is already signaled, this function will return -ENOENT (and - * *not* call the callback) + * *not* call the callback). * * Add a software callback to the fence. Same restrictions apply to - * refcount as it does to dma_fence_wait, however the caller doesn't need to - * keep a refcount to fence afterwards: when software access is enabled, - * the creator of the fence is required to keep the fence alive until - * after it signals with dma_fence_signal. The callback itself can be called - * from irq context. + * refcount as it does to dma_fence_wait(), however the caller doesn't need to + * keep a refcount to fence afterward dma_fence_add_callback() has returned: + * when software access is enabled, the creator of the fence is required to keep + * the fence alive until after it signals with dma_fence_signal(). The callback + * itself can be called from irq context. * * Returns 0 in case of success, -ENOENT if the fence is already signaled * and -EINVAL in case of error. @@ -286,7 +341,7 @@ EXPORT_SYMBOL(dma_fence_add_callback); /** * dma_fence_get_status - returns the status upon completion - * @fence: [in] the dma_fence to query + * @fence: the dma_fence to query * * This wraps dma_fence_get_status_locked() to return the error status * condition on a signaled fence. See dma_fence_get_status_locked() for more @@ -311,8 +366,8 @@ EXPORT_SYMBOL(dma_fence_get_status); /** * dma_fence_remove_callback - remove a callback from the signaling list - * @fence: [in] the fence to wait on - * @cb: [in] the callback to remove + * @fence: the fence to wait on + * @cb: the callback to remove * * Remove a previously queued callback from the fence. This function returns * true if the callback is successfully removed, or false if the fence has @@ -323,6 +378,9 @@ EXPORT_SYMBOL(dma_fence_get_status); * doing, since deadlocks and race conditions could occur all too easily. For * this reason, it should only ever be done on hardware lockup recovery, * with a reference held to the fence. + * + * Behaviour is undefined if @cb has not been added to @fence using + * dma_fence_add_callback() beforehand. */ bool dma_fence_remove_callback(struct dma_fence *fence, struct dma_fence_cb *cb) @@ -359,9 +417,9 @@ dma_fence_default_wait_cb(struct dma_fence *fence, struct dma_fence_cb *cb) /** * dma_fence_default_wait - default sleep until the fence gets signaled * or until timeout elapses - * @fence: [in] the fence to wait on - * @intr: [in] if true, do an interruptible wait - * @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT + * @fence: the fence to wait on + * @intr: if true, do an interruptible wait + * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT * * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the * remaining timeout in jiffies on success. If timeout is zero the value one is @@ -454,12 +512,12 @@ dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count, /** * dma_fence_wait_any_timeout - sleep until any fence gets signaled * or until timeout elapses - * @fences: [in] array of fences to wait on - * @count: [in] number of fences to wait on - * @intr: [in] if true, do an interruptible wait - * @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT - * @idx: [out] the first signaled fence index, meaningful only on - * positive return + * @fences: array of fences to wait on + * @count: number of fences to wait on + * @intr: if true, do an interruptible wait + * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT + * @idx: used to store the first signaled fence index, meaningful only on + * positive return * * Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if * interrupted, 0 if the wait timed out, or the remaining timeout in jiffies @@ -468,6 +526,8 @@ dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count, * Synchronous waits for the first fence in the array to be signaled. The * caller needs to hold a reference to all fences in the array, otherwise a * fence might be freed before return, resulting in undefined behavior. + * + * See also dma_fence_wait() and dma_fence_wait_timeout(). */ signed long dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count, @@ -540,19 +600,18 @@ EXPORT_SYMBOL(dma_fence_wait_any_timeout); /** * dma_fence_init - Initialize a custom fence. - * @fence: [in] the fence to initialize - * @ops: [in] the dma_fence_ops for operations on this fence - * @lock: [in] the irqsafe spinlock to use for locking this fence - * @context: [in] the execution context this fence is run on - * @seqno: [in] a linear increasing sequence number for this context + * @fence: the fence to initialize + * @ops: the dma_fence_ops for operations on this fence + * @lock: the irqsafe spinlock to use for locking this fence + * @context: the execution context this fence is run on + * @seqno: a linear increasing sequence number for this context * * Initializes an allocated fence, the caller doesn't have to keep its * refcount after committing with this fence, but it will need to hold a - * refcount again if dma_fence_ops.enable_signaling gets called. This can - * be used for other implementing other types of fence. + * refcount again if &dma_fence_ops.enable_signaling gets called. * * context and seqno are used for easy comparison between fences, allowing - * to check which fence is later by simply using dma_fence_later. + * to check which fence is later by simply using dma_fence_later(). */ void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
- Intro section that links to how this is exposed to userspace. - Lots more hyperlinks. - Minor clarifications and style polish v2: Add misplaced hunk of kerneldoc from a different patch. Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org --- Documentation/driver-api/dma-buf.rst | 6 ++ drivers/dma-buf/dma-fence.c | 147 +++++++++++++++++++-------- 2 files changed, 109 insertions(+), 44 deletions(-)