Re: net: dsa: Realtek switch drivers

[Chris Packham]

On 2/07/24 14:50, Andrew Lunn wrote:
> > What would I be loosing if I don't use the DSA infrastructure? I got kind of
> > hung up at the point where it really wanted a CPU port and I just couldn't
> > provide a nice discrete NIC.
>   
> DSA gives you a wrapper which handles some common stuff, which you
> will end up implementing if you do a pure switchdev driver. Mostly
> translating netdev to port index. The tagging part of DSA does not
> apply if you have DMA per user port, so you don't loose anything
> there.  I guess you cannot cascade multiple switches, so the D in DSA
> also does not apply. You do lose out on tcpdump support, since you
> don't have a conduit interface which all traffic goes through.
>
> But you should not try to impose DSA if it does not fit. There are
> 'simple' pure switchdev drivers, you don't need to try to understand
> the mellanox code. Look at the microchip drivers for something to
> copy.
One reason for using DSAI've just found is that in theory the RTL930x 
supports a CPU disabled mode where you do connect it to an external CPU 
and the data travels over SGMII like you'd get with a traditional DSA 
design. It's not a mode I'm planning on supporting anytime soon but it 
might come up when I get round to submitting some patches.