phy_loopback(9)

📦 version 7.3.1, in nixpkgs unstable

💅 phy_loopback — Kernel API Manual 💅

okay bestie, welcome to phy_loopback(9), straight out of the Kernel API Manual ✨ this one's all about making your PHY do the loopback thing. it's giving "networking but make it self-referential" 🌀

🌸 NAME 🌸

phy_loopback — configure loopback mode of PHY 💫

like literally, that's the whole vibe. you point it at a PHY and you turn loopback on or off. iconic behavior, no notes 👑

🎀 SYNOPSIS 🎀

int phy_loopback (struct phy_device *phydev , bool enable , int speed );

there she is. three args, one int coming back at you 🫶

🦋 ARGUMENTS 🦋

  • phydev — the target phy_device struct, aka the PHY you're doing all this to 💖 it's the main character here, honestly.
  • enable — a bool that says whether you're turning loopback mode on or off. flip the switch, bestie 🔘
  • speed — turn on loopback mode with a speed. yes, speed is part of the whole situation 🏎️✨

🌈 DESCRIPTION 🌈

so here's the tea ☕: this function configures loopback mode of the PHY — that's the core job, that's the assignment, she ate 💅

and also — and this is the part people forget — it signals link down and link up if the speed is changing 😭 like if you're switching speeds mid-loopback, the link gets the whole dramatic down-then-up moment. it's giving main character entrance, honestly 🎬

⭐ RETURN ⭐

  • 0 on success 🎉 slay, you did it
  • negative error code on failure 😭💀 something went sideways, go read the code
fr fr, check that return value. a negative number means it did not work, no cap.

💜 SEE ALSO 💜

all the siblings and cousins live in the kernel file ./drivers/net/phy/phy.c 🧚 and here's the whole family reunion, every single one of them:

and that's the whole page, bestie 🫶 this little gem lives in ./drivers/net/phy and it's dated October 2026 ⭐ so yeah, future-coded of her. go forth, configure some loopback, and remember: link down, link up, speed changing — she contains multitudes 💖✨🎀

📦 where this page comes from