On 10/07/15 14:02, Stas Sergeev wrote: > 10.07.2015 23:39, Florian Fainelli пишет: >>> - in-band status is an implementation delail, and it is >>> specific to a particular protocols. If you request the >>> in-band status for some protocol that doesn't support >>> it, perhaps you should get -EINVAL, because such a >>> config makes no sense. With autonegotiation, the rules >>> are not that strict: it can be "unimplemented", which doesn't >>> necessary mean nonsense in the config. >> So by specifying "autoneg", you are not specific about the kind of >> auto-negotiation protocol available, which is precisely my point: you >> need to go down to that level of detail for this to be useful. So maybe >> something like: >> >> autoneg = "in-band-status" would actually be a better thing in terms of >> description because then you would tell what can be made >> available/working? > I would agree with this if your argument below is true (see below). > >>> - autonegotiation is a wider term, and may be implemented >>> by some other means than the in-band status (which is >>> probably impossible for a fixed-link though). >>> >>> - In the terms that the driver uses, it is autonegotiation, eg >>> MVNETA_GMAC_AUTONEG_CONFIG. And when you go down >>> the implementation details, you see MVNETA_GMAC_INBAND_AN_ENABLE, >>> which is just one AN bit of many. >> But arguably, there could be another auto-negotiation method, which is >> not in-band status related, which means that you would need a way to >> distinguish between using in-band status, or using something else or >> nothing, would not you? > "something else" is a big question here. > Can you think of _any_ other way that is both not an MDIO > (suits to fixed-link) and not an in-band? Yes, I could think about I2C or SPI PHYs that you could use alongside an Ethernet controller that would qualify for out-of-band, not in-band, yet could still provide auto-negotiation. You may have special hardware with such a SPI or I2C controller which provides automatic decoding of the auto-neg registers. Have not looked at e.g: SFP form factors or fiber links, but they could also have additional out-of-band type of auto-negotiation available. > If the answer is yes (even theoretically), then > autoneg = "in-band" | "off" > may make sense. Otherwise boolean just looks enough. I think the answer is yes. > If we would implement autoneg outside of the fixed-link, > then its semantic would likely be > autoneg = "mdio" | "in-band" | "off" > But the fact that we put it under fixed-link where only a > single AN possibility exist, may probably be underlined by > a semantic specific to fixed-link. Right, if auto-negotiation was defined outside of fixed-link, that is indeed how I would also specify this. > > One may also argue that > autoneg = "any-possible-autoneg-that-works" is better than > specifying it explicitly, which is exactly what the boolean does. I prefer excess of information rather than lack of information, because you can always choose what to do with it. Especially when it comes to Device Tree, plan carefully :) -- Florian -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
