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    SubjectRe: [EXT] Re: [PATCH] bus: fsl-mc: Add ACPI support for fsl-mc
    > > But by design SFP, SFP+, and QSFP cages are not fixed function network
    > > adapters. They are physical and logical devices that can adapt to
    > > what is plugged into them. How the devices are exposed should be
    > > irrelevant to this conversation it is about the underlying
    > > connectivity.
    >
    > Apologies - I was under the impression that SFP and friends were a
    > physical-layer thing and that a MAC in the SoC would still be fixed such
    > that its DMA and interrupt configuration could be statically described
    > regardless of what transceiver was plugged in (even if some configurations
    > might not use every interrupt/stream ID/etc.) If that isn't the case I shall
    > go and educate myself further.

    Hi Robin

    It gets interesting with QSFP cages. The Q is quad, there are 4 SERDES
    lanes. You can use them for 1x 40G link, or you can split them into 4x
    10G links. So you either need one MAC or 4 MACs connecting to the
    cage, and this can change on the fly when a modules is ejected and
    replaced with another module. There are only one set of control pins
    for i2c, loss of signal, TX disable, module inserted. So where the
    interrupt/stream ID/etc are mapped needs some flexibility.

    There is also to some degree a conflict with hiding all this inside
    firmware. This is complex stuff. It is much better to have one core
    implementing in Linux plus some per hardware driver support, than
    having X firmware blobs, generally closed source, each with there own
    bugs which nobody can fix.

    Andrew

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