mdiobus_write(9)

🌸 NAME 🌸

mdiobus_write — bestie, it's literally the convenience function for writing a given MII mgmt register. That's the whole vibe. ✨

This is the mdiobus_write(9) page from the Kernel API Manual, and we're gonna make it make sense. 💖

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✨ SYNOPSIS ✨

Here's the exact signature, no cap:

int mdiobus_write (struct mii_bus *bus , int addr , u32 regnum , u16 val
);

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🎀 ARGUMENTS 🎀

• bus — the mii_bus struct.
• addr — the phy address.
• regnum — register number to write.
• val — value to write to regnum.

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💖 RETURN 💖

Zero if successful, negative error code on failure. So 0 is the slay outcome, and a negative number means something went sideways 😭.

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⚠️ NOTE ⚠️

MUST NOT be called from interrupt context, because the bus read/write functions may wait for an interrupt to conclude the operation. This is not a drill, bestie — interrupt context is a hard no 💀.

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👀 SEE ALSO 👀

Kernel file ./drivers/net/phy/mdio_bus.c is where this lives, and the related squad is:

• __mdiobus_read(9)
• __mdiobus_write(9)
• __mdiobus_modify_changed(9)
• __mdiobus_c45_read(9)
• __mdiobus_c45_write(9)
• __mdiobus_c45_modify_changed(9)
• mdiobus_read_nested(9)
• mdiobus_read(9)
• mdiobus_c45_read(9)
• mdiobus_c45_read_nested(9)
• mdiobus_write_nested(9)
• mdiobus_c45_write(9)
• mdiobus_c45_write_nested(9)
• mdiobus_modify(9)
• mdiobus_c45_modify(9)
• mdiobus_modify_changed(9)
• mdiobus_c45_modify_changed(9)

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Okay that's the whole page, bestie 🫶 — source/version path ./drivers/net/phy, dated October 2026, and yes, it's the mdiobus_write(9) manual page. Periodt. 💅