On Tue, 2019-06-18 at 22:55 +0200, Arnd Bergmann wrote: > On Tue, Jun 18, 2019 at 10:36 PM Johannes Berg > <johannes@xxxxxxxxxxxxxxxx> wrote: > > > > On Tue, 2019-06-18 at 21:59 +0200, Arnd Bergmann wrote: > > > > > > From my understanding, the ioctl interface would create the lower > > > netdev after talking to the firmware, and then user space would use > > > the rmnet interface to create a matching upper-level device for that. > > > This is an artifact of the strong separation of ipa and rmnet in the > > > code. > > > > Huh. But if rmnet has muxing, and IPA supports that, why would you ever > > need multiple lower netdevs? > > From my reading of the code, there is always exactly a 1:1 relationship > between an rmnet netdev an an ipa netdev. rmnet does the encapsulation/ > decapsulation of the qmap data and forwards it to the ipa netdev, > which then just passes data through between a hardware queue and > its netdevice. I'll take your word for it. Seems very odd, given that the whole point of the QMAP header seems to be ... muxing? > [side note: on top of that, rmnet also does "aggregation", which may > be a confusing term that only means transferring multiple frames > at once] Right, but it's not all that much interesting in the context of this discussion. > Sure, I definitely understand what you mean, and I agree that would > be the right way to do it. All I said is that this is not how it was done > in rmnet (this was again my main concern about the rmnet design > after I learned it was required for ipa) ;-) :-) Well, I guess though if the firmware wants us to listen to those on/off messages we'll have to do that one way or the other. Oh. Maybe it's just *because* rmnet is layered on top, and thus you fundamentally cannot do flow control the way I described - not because you have multiple session on the same hardware ring, but because you abstracted the hardware ring away too much ... johannes
