Hello, On Fri, 4 May 2018 19:23:37 +0200, Antoine Tenart wrote:
> On Fri, May 04, 2018 at 10:04:48AM -0700, Florian Fainelli wrote: > > On 05/04/2018 06:56 AM, Antoine Tenart wrote: > > > SFP connectors can be solder on a board without having any of their pins > > > (LOS, i2c...) wired. In such cases the SFP link state cannot be guessed, > > > and the overall link status reporting is left to other layers. > > > > > > In order to achieve this, a new SFP_DEV status is added, named UNKNOWN. > > > This mode is set when it is not possible for the SFP code to get the > > > link status and as a result the link status is reported to be always UP > > > from the SFP point of view. > > > > Why represent the SFP in Device Tree then? Why not just declare this is > > a fixed link which would avoid having to introduce this "unknown" state. > > The other solution would have been to represent this as a fixed-link. > But such a representation would report the link as being up all the > time, which is something we wanted to avoid as the GoP in PPv2 can > report some link status. This is achieved using SFP+phylink+PPv2. > > And representing the SFP cage in the device tree, although it's a > "dummy" one, helps describing the hardware. Just to add to this: the board physically has a SFP cage, and a cable can be connected to it, or not. So it is absolutely not a fixed link (cable can be connected or not) and it really is a SFP cage. Best regards, Thomas -- Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
