__phy_modify_changed(9)

💖 __phy_modify_changed(9) — Kernel API Manual, but make it make sense 💖

okay bestie, sit down, because today we're reading a page from the Kernel API Manual and honestly? she's short but she's iconic. this is __phy_modify_changed, and yes the double underscore is doing main character energy, it's part of the name, don't touch it 💅

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✨ NAME ✨

__phy_modify_changed — the convenience function for modifying a PHY register 🎀

like, she's the girl who does one job and does it well. no cap.

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🌸 SYNOPSIS 🌸

int __phy_modify_changed (struct phy_device *phydev , u32 regnum , u16
mask , u16 set );

that's the whole signature, character for character, go off 👑

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🦋 ARGUMENTS 🦋

• phydev — a pointer to a struct phy_device 🫶 (your PHY, your bestie, the whole reason we're here)
• regnum — register number 📍 literally just which register we're messing with
• mask — bit mask of bits to clear 🧹 the ones getting yeeted
• set — bit mask of bits to set ⭐ the ones getting their moment

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💀 DESCRIPTION 💀

so here's the thing: she's an unlocked helper function, which means the locking is not her problem, she said not today 😭 but what she does do is let a PHY register be modified, and the math is literally this:

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

read it slowly bestie, it slaps: take the old value, AND it with ~mask so everything in mask gets wiped, then OR in set so those bits go up. clear then set. that's the whole vibe check 🧚

and the returns? listen:

• negative errno — something went wrong 😭
• 0 — there was no change
• 1 — in case of change 🎉

yes, zero means "nothing happened" and one means "we moved", do not mix them up i'm begging 🙈

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💜 SEE ALSO 💜

Kernel file ./include/linux/phy.h

okay this list is long but she ate and we're listing every single one, no skipping, periodt 🔥

• enum phy_interface_t(9)
• phy_modes(9)
• rgmii_clock(9)
• struct mdio_bus_stats(9)
• struct mii_bus(9)
• mdiobus_alloc(9)
• enum phy_state(9)
• struct phy_c45_device_ids(9)
• struct phy_oatc14_sqi_capability(9)
• struct phy_device(9)
• struct phy_tdr_config(9)
• enum link_inband_signalling(9)
• struct phy_plca_cfg(9)
• struct phy_plca_status(9)
• struct phy_led(9)
• struct phy_mse_capability(9)
• struct phy_mse_snapshot(9)
• struct phy_driver(9)
• phy_id_compare(9)
• phy_id_compare_vendor(9)
• phy_id_compare_model(9)
• phydev_id_compare(9)
• phy_is_started(9)
• phy_driver_is_genphy(9)
• phy_disable_eee_mode(9)
• phy_can_wakeup(9)
• phy_may_wakeup(9)
• phy_read(9)
• __phy_read(9)
• phy_write(9)
• __phy_write(9)
• phy_read_mmd_poll_timeout(9)
• __phy_set_bits(9)
• __phy_clear_bits(9)
• phy_set_bits(9)
• phy_clear_bits(9)
• __phy_set_bits_mmd(9)
• __phy_clear_bits_mmd(9)
• phy_set_bits_mmd(9)
• phy_clear_bits_mmd(9)
• phy_interrupt_is_valid(9)
• phy_polling_mode(9)
• phy_has_hwtstamp(9)
• phy_has_rxtstamp(9)
• phy_has_tsinfo(9)
• phy_has_txtstamp(9)
• phy_is_default_hwtstamp(9)
• phy_on_sfp(9)
• phy_interface_mode_is_rgmii(9)
• phy_interface_mode_is_8023z(9)
• phy_interface_is_rgmii(9)
• phy_is_pseudo_fixed_link(9)
• phy_module_driver(9)

like i said. every. single. one. 💅✨

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ngl bestie, quick reminder: this page lives in the kernel API docs, so if the kernel changes and the docs say otherwise, the kernel wins. always. 😭🙈

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🌈 and that's the whole page!! sourced from ./include/linux, dated October 2026, filed under the manual as __phy_modify_changed(9) — mwah, go read a register, ily, bye 🫶💖🎀