The 05/19/2020 16:37, Vinicius Costa Gomes wrote: > > Andre Guedes <andre.gue...@intel.com> writes: > > > Hi, > > > > Quoting Vinicius Costa Gomes (2020-05-15 18:29:44) > >> One example, for retrieving and setting the configuration: > >> > >> $ ethtool $ sudo ./ethtool --show-frame-preemption enp3s0 > >> Frame preemption settings for enp3s0: > >> support: supported > >> active: active > > > > IIUC the code in patch 2, 'active' is the actual configuration knob that > > enables or disables the FP functionality on the NIC. > > > > That sounded a bit confusing to me since the spec uses the term 'active' to > > indicate FP is currently enabled at both ends, and it is a read-only > > information (see 12.30.1.4 from IEEE 802.1Q-2018). Maybe if we called this > > 'enabled' it would be more clear. > > Good point. Will rename this to "enabled". > > > > >> supported queues: 0xf > >> supported queues: 0xe > >> minimum fragment size: 68 > > > > I'm assuming this is the configuration knob for the minimal non-final > > fragment > > defined in 802.3br. > > > > My understanding from the specs is that this value must be a multiple from > > 64 > > and cannot assume arbitrary values like shown here. See 99.4.7.3 from IEEE > > 802.3 and Note 1 in S.2 from IEEE 802.1Q. In the previous discussion about > > FP, > > we had this as a multiplier factor, not absolute value. > > I thought that exposing this as "(1 + N)*64" (with 0 <= N <= 3) that it > was more related to what's exposed via LLDP than the actual capabilities > of the hardware. And for the hardware I have actually the values > supported are: (1 + N)*64 + 4 (for N = 0, 1, 2, 3). > > So I thought I was better to let the driver decide what values are > acceptable. > > This is a good question for people working with other hardware. >
I think it's most intuitive to use the values for AddFragSize as described in 802.3br (N = 0, 1, 2, 3). You will anyway have to use one of these values when you want to expose the requirements of your receiver through LLDP. > > -- > Vinicius -- Joergen Andreasen, Microchip
