On Tue. 20 Feb. 2024 at 17:35, Vincent Mailhol <vincent.mailhol@xxxxxxxxx> wrote: > On Tue. 20 Feb. 2024 at 17:10, Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> wrote: > > > > On 20.02.2024 08:49:26, Dr. Michael 'Mickey' Lauer wrote: > > > Hi Marc, > > > > > > >> > > > >> Sounds pretty cool. Our design is based on an ESP32-S3 though, so I > > > >> have to duplicate that effort. Is there some kind of USB protocol > > > >> definition for what gs-usb expects or do I need to learn that from the > > > >> implementation? > > > > > > > > I've put together a very rough summary of the driver's side of view: > > > > > > > > https://gist.github.com/marckleinebudde/99f72d9db67accf08cc6efa367cfe54b > > > > > > > > Feel free to update. > > > > > > Wow, that’s very kind of you! > > > > :) > > > > > Later this year I’ll take this blueprint to implement the necessary > > > changes in our firmware. I’ll enhance / update your summary > > > as I’ll go. > > > > If you discover any odd points or areas for improvement in the USB > > protocol, please let us know. > > > > Currently, TX-complete sends the _entire_ structure back to the host, > > which is quite an overhead, especially for CAN FD frames. We're working > > on a "short-tx-complete" feature. > > The es581.4 may be doing what you are looking for: > > - When sending a frame, the driver attaches a 32 bit index: > https://elixir.bootlin.com/linux/v6.7/source/drivers/net/can/usb/etas_es58x/es581_4.h#L78 > - When receiving the TX completion message, the device just send > back that index and a timestamp: > https://elixir.bootlin.com/linux/v6.7/source/drivers/net/can/usb/etas_es58x/es581_4.h#L97 > > The device is agnostic of what this index represents. The driver uses > the index from the can_put_echo_skb() / can_get_echo_skb(). > > (in addition the driver can handle bulk send and receive but that's > another story). I forgot to mention: it is also perfectly fine not to use the index as long as you can guarantee that the TX completion messages are received in order (which is not hard to achieve). In which case, the TX completion message can be as simple as just a timestamp. Yours sincerely, Vincent Mailhol
