Hello, during my implementation of a zero copy port to stm32f4 I ran into some difficulties. As in presumably all implementations, a dma chain/ring is used to exchance data with the MAC core. I do fill the related dma descriptors with lwip pbufs (well, custom buffers, read below). However a situation might arise, when there is no pbuf left when a receive dma descriptor shall be "rearmed". I could not find a mechanism where lwip notifies me that a lwip-pbuf is available again, so I think I would have to poll lwip for buffers, which is out of question. That's why I felt I had to use custom pbufs, because through the custom pbuf deleter functions I am notified in such situations. (Please correct me if I'm wrong alltogether, I would gladly like to use lwips standard buffers, because currently I have to manage a second "heap-like" buffer ring of custom pbufs because of that). Now during my custom pbuf usage I ran across situations, were lwip would call mem_trim or other such functions, not checking for whether the custom-pbuf-flag is set. A notable occasion would f.e. be in line "pbuf.c":417. In my eyes it might be a lot clearer if custom pbufs are not indicated by a flag bit, but by their own type maybe?
Kind Regards, Michael _______________________________________________ lwip-users mailing list lwip-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/lwip-users
