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 > > 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..? -- ~Vinod
