pcs_pre_init(9)

💅 pcs_pre_init(9) — like, the Kernel API Manual, but make it make sense

Okay bestie, so this one is from the Kernel API Manual, and it's literally called pcs_pre_init — the little pre-game ritual your PCS has to do before the MAC can even think about waking up. 🫶

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✨ NAME ✨

pcs_pre_init — configure the PCS components that are, like, necessary for MAC initialization. No PCS prep, no MAC glow-up. 💅

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🌸 SYNOPSIS 🌸

int pcs_pre_init (struct phylink_pcs *pcs );

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🎀 ARGUMENTS 🎀

• pcs — a pointer to a struct phylink_pcs. That's it. That's the whole vibe check. ✨

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🦋 DESCRIPTION 🦋

So here's the tea: MAC drivers can call this through the phylink_pcs_pre_init wrapper, and they have to do it before their hardware gets initialized. Like, before. ⏰

🚨 Not me telling you this: do not call it after the link is brought up. Reconfiguring the PCS at that point could literally break the link. It's giving chaos, and not the cute kind. 💀

Some MAC devices need their associated PCS device to do a very specific hardware initialization first, because otherwise they can't properly initialize their own hardware. Real example: initializing stmmac controllers requires an active REF_CLK signal served up by the PHY/PCS. Iconic of them, honestly. 👑

So by calling phylink_pcs_pre_init, MAC drivers can make sure the PCS is set up in a way that lets hardware initialization actually succeed. Slay. ✅

Now — the specific configuration that pcs_pre_init performs depends on the model of PCS and on the requirements of the MAC device attached to it. So if you're a PCS driver author, lowkey consider whether your target device is going to be used together with a MAC device whose driver calls phylink_pcs_pre_init. And if you're a MAC driver author, please document your requirements for the PCS pre-initialization. Do it for the girls. 📝💖

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💜 SEE ALSO 💜

Kernel file ./include/linux/phylink.h, plus the whole friend group:

• struct phylink_link_state(9)
• struct phylink_config(9)
• struct phylink_mac_ops(9)
• mac_get_caps(9)
• mac_select_pcs(9)
• mac_prepare(9)
• mac_config(9)
• mac_finish(9)
• mac_link_down(9)
• mac_link_up(9)
• mac_disable_tx_lpi(9)
• mac_enable_tx_lpi(9)
• mac_wol_set(9)
• struct phylink_pcs(9)
• struct phylink_pcs_ops(9)
• pcs_validate(9)
• pcs_inband_caps(9)
• pcs_enable(9)
• pcs_disable(9)
• pcs_get_state(9)
• pcs_config(9)
• pcs_an_restart(9)
• pcs_link_up(9)
• pcs_disable_eee(9)
• pcs_enable_eee(9)
• phylink_get_link_timer_ns(9)
• phylink_mac_implements_lpi(9)

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And that's the whole page, bestie! 🧚‍♀️ This one lives under ./include/linux, dated October 2026, and it answers to the name pcs_pre_init(9). Go forth and pre-init responsibly. 💖✨🎀