On 01-02-19, 09:59, Federico Vaga wrote: > > > On February 1, 2019 4:17:50 AM UTC, Vinod Koul <vkoul@xxxxxxxxxx> wrote: > >On 28-01-19, 09:47, Federico Vaga wrote: > >> Hi, > >> > >> I have a new question concerning documentation. > >> > >> > >https://www.kernel.org/doc/html/latest/driver-api/dmaengine/client.html > >> > >> >From this document it is not really clear, at least to me, if > >clients can > >> consider valid the `struct dma_async_tx_descriptor` after submission > >to the > >> DMA engine. > > > >Nope they can't and should not touch the descriptor after submission. > >The client get cookie and that is supposed to be used > > Good, thanks > > > >> > >> Clients get a TX descriptor from a DMA engine using things like > >> `dmaengine_prep_*`. These calls - may - allocate new descriptors and > >return > >> them to the caller; this may include other structures which are not > >visible to > >> clients. So, if my understanding is correct, this means that it's the > >DMA > >> engine that, on TX completion, releases any TX descriptor allocated > >by > >> `dmaengine_prep_*`. This implies that the pointer that the client is > >using > >> must be considered invalid right after `dmaengine_submit()`. > >> If what I understood by reading the documentation and the code is > >correct, > >> then I think that this should be mentioned in the Documentation. > >> If I'm wrong, please tell me where :) > > > >And what exactly are you trying to do here..? > Please wrap your replies within 80chars > What if I answer: "the right thing"? Joking. I just expressed my > understanding of something which is not documented properly (my > opinion). I wanted to be sure that the logic, the reasons behind are > the ones that I understood. I will propose a patch to the > documentation, unless you want to do it. -- Inviato dal mio > dispositivo Android con K-9 Mail. Perdonate la brevità. Sure please feel free to send a patch :) Mostly people ask these questions based on a driver they are working off, and it makes sense to fix the assumptions by asking what they are trying to achieve... -- ~Vinod
