On Fri, Jun 26, 2020 at 2:21 PM Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx> wrote: > > Trying to explain a bit how this thing works. In my opinion diagrams > are a bit easier to understand than words. kerneldoc supports in-line DOT graphs, see e.g. https://dri.freedesktop.org/docs/drm/gpu/drm-kms.html#overview If that doesn't work, then you can include a full-blown svg too. And yes for this a quick DOT graph that explains how things connect sound like the perfect use of a diagramm. Cheers, Daniel > > Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx> > --- > drivers/dma-buf/dma-fence-chain.c | 37 +++++++++++++++++++++++++++++++ > 1 file changed, 37 insertions(+) > > diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c > index 3d123502ff12..ac90ddf37b55 100644 > --- a/drivers/dma-buf/dma-fence-chain.c > +++ b/drivers/dma-buf/dma-fence-chain.c > @@ -9,6 +9,43 @@ > > #include <linux/dma-fence-chain.h> > > +/** > + * DOC: DMA fence chains overview > + * > + * DMA fence chains, represented by &struct dma_fence_chain, are a kernel > + * internal synchronization primitive providing a wrapping mechanism of other > + * DMA fences in the form a single link list. > + * > + * One of the use case of this primitive is to implement Vulkan timeline > + * semaphores (see VK_KHR_timeline_semaphore extension or Vulkan specification > + * 1.2). > + * > + * Each DMA fence chain item wraps 2 items : > + * > + * - A previous DMA fence. > + * > + * - A DMA fence associated to the current &struct dma_fence_chain. > + * > + * A DMA fence chain becomes signaled when its previous fence as well as its > + * associated fence are signaled. If a chain of dma fence chains is created, > + * this property recurses, meaning that any dma fence chain element in the > + * list becomes signaled only if its associated fence and all the previous > + * fences in the chain are also signaled. > + * > + * A DMA fence chain's seqno is specified through dma_fence_chain_init(). This > + * value is lower bound to the seqno of the previous fence to ensure the chain > + * is monotically increasing. > + * > + * By traversing the chain's linked list, one can compute a seqno number > + * associated with the chain such that is the highest number for which all > + * previous fences have signaled. > + * > + * One can also traverse the chain's linked list to find a &struct > + * dma_fence_chain that when signaled guarantees that all previous fences in > + * the chain are signaled. dma_fence_chain_find_seqno() provides this > + * functionality. > + */ > + > static bool dma_fence_chain_enable_signaling(struct dma_fence *fence); > > /** > -- > 2.27.0 > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
