cxgb4_change_mac(9)

💅 cxgb4_change_mac — the Kernel API Manual, bestie edition 🎀

Okay so we're deep in the cxgb4 trenches today, and this one is cxgb4_change_mac(9) — literally the glow-up operation for a MAC address filter. She changes outfits mid-party and nobody even notices. Iconic.

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✨ NAME ✨

cxgb4_change_mac — update the match filter for a MAC address. That's it, that's the whole gig. A little MAC-address makeover. 💖

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✨ SYNOPSIS ✨

int cxgb4_change_mac (struct port_info *pi , unsigned int viid , int
*tcam_idx , const u8 *addr , bool persist , u8 *smt_idx );

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✨ ARGUMENTS ✨

• pi — the port_info. The port's whole personality file, honestly.
• viid — the VI id. Not "vibe id," but honestly close enough.
• tcam_idx — the TCAM index of the existing filter for the old value of the MAC address, or -1. So: give her the old receipt, or hand over -1 and she'll start fresh. 🧾
• addr — the new MAC address value. The new look. The new lewk, if you will.
• persist — whether a new MAC allocation should be persistent. Keeping it around vs. ghosting later.
• smt_idx — the destination to store the new SMT index. She writes it there, you go read it. Cooperative queen behavior. 👑

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🌸 DESCRIPTION 🌸

So here's the tea: this function modifies an MPS filter and sets it to the new MAC address if tcam_idx >= 0. Like, you already had a filter, she just updates it in place. Slay, no drama.

But if tcam_idx < 0, she adds the MAC address to a brand-new filter instead. And in that case — the new-filter case — the address is added persistently if persist is true. Lowkey important distinction, ngl.

And babe, listen: addresses are programmed to the hash region if the TCAM runs out of entries. So there's a fallback. She's resourceful. 🦋

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👑 SEE ALSO 👑

Kernel file ./drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c — the mothership, the main character's address, iykyk.

Plus the whole friend group:

• cxgb4_write_rss(9)
• setup_rss(9)
• setup_sge_queues(9)
• cxgb4_set_rspq_intr_params(9)
• cxgb4_create_server(9)
• cxgb4_best_mtu(9)
• cxgb4_best_aligned_mtu(9)
• cxgb4_port_chan(9)
• cxgb4_port_e2cchan(9)
• cxgb4_port_viid(9)
• cxgb4_port_idx(9)
• cxgb_up(9)

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And that's the whole page, bestie. 🌈 Cute little sign-off time: this gem lives in ./drivers/net/ethernet/chelsio..., dated October 2026, and the source/version tag on the footer is cxgb4_change_mac(9). Periodt. 💅✨