Hi Alex, aahringo@xxxxxxxxxx wrote on Mon, 6 Jun 2022 23:04:06 -0400: > Hi, > > On Mon, Jun 6, 2022 at 11:43 AM Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote: > > > > Hi Alexander, > > > > aahringo@xxxxxxxxxx wrote on Fri, 3 Jun 2022 22:01:38 -0400: > > > > > Hi, > > > > > > On Fri, Jun 3, 2022 at 2:34 PM Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote: > > > > > > > > The current enum is wrong. A device can either be an RFD, an RFD-RX, an > > > > RFD-TX or an FFD. If it is an FFD, it can also be a coordinator. While > > > > defining a node type might make sense from a strict software point of > > > > view, opposing node and coordinator seems meaningless in the ieee > > > > 802.15.4 world. As this enumeration is not used anywhere, let's just > > > > drop it. We will in a second time add a new "node type" enumeration > > > > which apply only to nodes, and does differentiates the type of devices > > > > mentioned above. > > > > > > > > > > First you cannot say if this is not used anywhere else. > > > > Mmmh, that's tricky, I really don't see how that might be a > > problem because there is literally nowhere in the kernel that uses this > > type, besides ieee802154_setup_sdata() which would just BUG() if this > > type was to be used. So I assumed it was safe to be removed. > > > > this header is somehow half uapi where we copy it into some other > software e.g. wpan-tools as you noticed. > > > > Second I have > > > a different opinion here that you cannot just "switch" the role from > > > RFD, FFD, whatever. > > > > I agree with this, and that's why I don't understand this enum. > > > > A device can either be a NODE (an active device) or a MONITOR (a > > passive device) at a time. We can certainly switch from one to > > another at run time. > > > > A NODE can be either an RFD or an FFD. That is a static property which > > cannot change. > > > > However being a coordinator is just an additional property of a NODE > > which is of type FFD, and this can change over time. > > > > So I don't get what having a coordinator interface would bring. What > > was the idea behind its introduction then? > > > > There exists arguments which I have in my mind right now: > > 1. frame parsing/address filter (which is somehow missing in your patches) > > The parsing of frames is different from other types (just as monitor > interfaces). You will notice that setting up the address filter will > require a parameter if coordinator or not. I think this is something that I completely missed until now, can you point me to where/how this is expected to be done? I don't see anything wpan specific filtering implementation. What is expected on this area and is there code that I missed already? > Changing the address > filterung during runtime of an interface is somehow _not_ supported. > The reason is that the datasheets tell you to first set up an address > filter and then switch into receiving mode. Changing the address > filter during receive mode (start()/stop()) is not a specified > behaviour. Due to bus communication it also cannot be done atomically. > This might be avoidable but is a pain to synchronize if you really > depend on hw address filtering which we might do in future. It should > end in a different receiving path e.g. node_rx/monitor_rx. Got it. > > 2. HardMAC transceivers > > The add_interface() callback will be directly forwarded to the driver > and the driver will during the lifetime of this interface act as a > coordinator and not a mixed mode which can be disabled and enabled > anytime. I am not even sure if this can ever be handled in such a way > from hardmac transceivers, it might depend on the transceiver > interface but we should assume some strict "static" handling. Static > handling means here that the transceiver is unable to switch from > coordinator and vice versa after some initialization state. Okay. I just completely missed the "interface add" command. So your advice is to treat the "PAN coordinator" property as a static property for a given interface, which seems reasonable. For now I will assume the same treatment when adding the interface is required compared to a NODE, but if something comes to your mind, please let me know. By the way, is there a mechanism limiting the number of interfaces on a device? Should we prevent the introduction of a coordinator iface if there is a node iface active? > 3. coordinator (any $TYPE specific) userspace software > > May the main argument. Some coordinator specific user space daemon > does specific type handling (e.g. hostapd) maybe because some library > is required. It is a pain to deal with changing roles during the > lifetime of an interface and synchronize user space software with it. > We should keep in mind that some of those handlings will maybe be > moved to user space instead of doing it in the kernel. I am fine with > the solution now, but keep in mind to offer such a possibility. > > I think the above arguments are probably the same why wireless is > doing something similar and I would avoid running into issues or it's > really difficult to handle because you need to solve other Linux net > architecture handling at first. Yep. > > > You are mixing things here with "role in the network" and what the > > > transceiver capability (RFD, FFD) is, which are two different things. > > > > I don't think I am, however maybe our vision differ on what an > > interface should be. > > > > > You should use those defines and the user needs to create a new > > > interface type and probably have a different extended address to act > > > as a coordinator. > > > > Can't we just simply switch from coordinator to !coordinator (that's > > what I currently implemented)? Why would we need the user to create a > > new interface type *and* to provide a new address? > > > > Note that these are real questions that I am asking myself. I'm fine > > adapting my implementation, as long as I get the main idea. > > > > See above. That's okay for me. I will adapt my implementation to use the interface thing. In the mean time additional details about what a coordinator interface should do differently (above question) is welcome because this is not something I am really comfortable with. Thanks, Miquèl