On 30-07-18, 12:46, Peter Ujfalusi wrote: > Vinod, > > On 2018-07-24 14:14, Vinod wrote: > >>>> Clients must not mix the two way of handling the metadata. > >>>> The set_len() is intended to tell the DMA driver the client provided > >>>> metadata size (in MEM_TO_DEV case mostly). > >>>> > >>>> MEM_TO_DEV flow on client side: > >>>> get_ptr() > >>>> fill in the metadata to the pointer (not exceeding max_len) > >>>> set_len() to tell the DMA driver the amount of valid bytes written > >>>> > >>>> DEV_TO_MEM flow on client side: > >>>> In the completion callback, get_ptr() > >>>> the metadata is payload_len bytes and can be accessed in the return > >>>> pointer. > >>> > >>> I would think to unify this.. > >> > >> I have tried it, but the attach mode and the pointer mode is hard to > >> handle with a generic API. > >> I will try to find a way to unify things in a sane way. > > > > Hmmm, looking from the description they will be for different methods, > > so lets make them orthogonal and not allow driver to register both. > > I would allow DMA drivers to register both, but somehow enforce that > clients are not mixing the two distinct way of dealing with the metadata. > > The reason for that is for example the attach mode is the simplest (I > implemented it first and I have a client using it), but if the pointer > mode is found to be more efficient and feasible for the DMA then the DMA > driver can implement that mode and the client can move as well w/o > breaking anything.
Sounds reasonable... -- ~Vinod
