yt8521_modif...p_fiber_bmcr(9)

📦 version 7.3.1, in nixpkgs unstable

💅 yt8521_modify_utp_fiber_bmcr

okay bestie, so this is a page straight out of the Kernel API Manual — yes, that manual — and it's about poking at a PHY's BMCR register. stay with me, it's actually cute 🎀

✨ NAME ✨

yt8521_modify_utp_fiber_bmcr — bits-modify a PHY's BMCR register 🦋

🌸 SYNOPSIS 🌸

int yt8521_modify_utp_fiber_bmcr (struct phy_device *phydev , u16 mask ,
u16 set );

💖 ARGUMENTS 💖

  • phydev — the phy_device struct. the main character, honestly 👑
  • mask — bit mask of bits to clear. the "not me deleting these bits" energy 🙈
  • set — bit mask of bits to set. the "slay, we're turning these ON" energy ✨

⭐ NOTE ⭐

so this is a convenience function that lets you modify a PHY's BMCR register like this, and I need you to memorize the formula fr fr:

new register value = (old register value & ~mask) | set 💅

here's the tea on YT8521: it has two space (utp/fiber) and three mode (utp/fiber/poll), and each space has MII_BMCR. poll mode combines utp and faber, so you need to do both. no cap, both of them 😭

it returns 0 or a negative errno code — so check that return value, bestie, don't just vibe past it 🌈

lowkey important: the return being a negative errno code means a bad time is possible. treat a non-zero return as your sign from the universe 💀

🔥 SEE ALSO 🔥

Kernel file ./drivers/net/phy/motorcomm.c — and honestly the whole friend group shows up here:

and that's the whole page, bestie 🫶 this one lives in ./drivers/net/phy, dated October 2026, and the header/footer vibe check was yt8521_modif...p_fiber_bmcr(9) on both ends. go forth and modify those bits 💜🍓

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