Re: [PATCH net-next v4 06/11] net: stmmac: resetup XPCS according to the new interface mode

[Choong Yong Liang]

On 1/2/2024 4:38 pm, Russell King (Oracle) wrote:
> Note the "This must not modify any state." statement. By reinitialising
> the PCS in this method, you are violating that statement.
>
> This requirement is because this method will be called by
> phylink_validate_mac_and_pcs() at various times, potentially for each
> and every interface that stmmac supports, which will lead to you
> reinitialising the PCS, killing the link, each time we ask the MAC for
> a PCS, whether we are going to make use of it in that mode or not.
>
> You can not do this. Sorry. Hard NAK for this approach.
Thank you for taking the time to review, got your concerns, and I'll 
address the following concerns before submitting a new patch series:

1. Remove allow_switch_interface and have the PHY driver fill in 
phydev->possible_interfaces.
2. Rework on the PCS to have similar implementation with the following 
patch "net: macb: use .mac_select_pcs() interface" 
(https://lore.kernel.org/netdev/E1n568J-002SZX-Gr@xxxxxxxxxxxxxxxxxxxxxx/T/).

Kindly let me know if there are any additional concerns or suggestions.