oneDragon[m]: > <@onedragon424:matrix.org> I have a very novice question.
> Currently, I'm looking at something about Raspberry Pi network interface cards.
> 
> I found that GPIO provides a kind of alternative function named RGMII\_MDIO, but seems it's implement(raspi linux) haven't used this kind of method, but Instead, it uses a direct address manipulation via MMIO to use MDIO (At least from my perspective it directly write int into MMIO mem.）
> Are there any special considerations in the implementation of this section?

RGII / MDIO is the interface to communicate with the external ethernet PHY using ISO (?) standard protocols, so generally if the GPIO is in RGMII_MDIO mode, you don't directly use it from software but let the ethernet control peripheral drive communications. So to indirectly use the RGMII interface, you'd perform operations with the ethernet controller