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..? 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.
