ntb_peer_db_set(9)

💅 ntb_peer_db_set — from the ntb_peer_db_set(9) chapter of the Kernel API Manual

okay bestie, so this is a kernel API page, part of the kernel API manual — we're literally in the drivers/ntb ✨ doorbell ✨ zone today. no cap, it's a tiny function with big "hey other side, look over here" energy.

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🌸 NAME 🌸

ntb_peer_db_set — set bits in the peer doorbell register 🛎️

Like, you're poking the other side's doorbell. Rude? No. Iconic? Yes.

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🎀 SYNOPSIS 🎀

int ntb_peer_db_set (struct ntb_dev *ntb , u64 db_bits );

the way that signature just sits there being all int-returning and tidy... we love a function that tells you if it worked. 😌

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🦋 ARGUMENTS 🦋

• ntb — your NTB device context. the main character struct, basically 💖
• db_bits — the doorbell bits you wanna set. these are your bits, pick them wisely ✨

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🫶 DESCRIPTION 🫶

okay so what this does: it sets bits in the peer doorbell register — the peer's, not yours, that's the whole point — and setting those bits may generate a peer doorbell interrupt on the other side. so, yeah, you're ringing their bell 🔔.

and here's the rule that's lowkey the most important part, no exceptions:

Bits that were already set must remain set. periodt. 💅 you're setting bits, not clearing them, not toggling them, not doing an unhinged little rewrite of the register. already-set bits stay set. fr fr.

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🔥 RETURN 🔥

• Zero on success 🎉 — zero is a win here, do not @ me
• otherwise an error number — so if it's not zero, it's giving error vibes and you should handle that 💀

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⭐ SEE ALSO ⭐

the bestie list is LONG, so buckle in. first up, the header that started it all:

• Kernel file ./include/linux/ntb.h 👑

enums + structs (the lore):

• enum ntb_topo(9), enum ntb_speed(9), enum ntb_width(9), enum ntb_default_port(9)
• struct ntb_client_ops(9), struct ntb_ctx_ops(9), struct ntb_dev_ops(9), struct ntb_client(9), struct ntb_dev(9)

register / unregister:

• ntb_register_client(9), ntb_unregister_client(9), ntb_register_device(9), ntb_unregister_device(9)

ctx + events:

• ntb_set_ctx(9), ntb_clear_ctx(9), ntb_link_event(9), ntb_db_event(9), ntb_msg_event(9)

ports (so many ports):

• ntb_default_port_number(9), ntb_default_peer_port_count(9), ntb_default_peer_port_number(9), ntb_default_peer_port_idx(9)
• ntb_port_number(9), ntb_peer_port_count(9), ntb_peer_port_number(9)
• ntb_logical_port_number(9), ntb_peer_logical_port_number(9), ntb_peer_port_idx(9)

links:

• ntb_link_is_up(9), ntb_link_enable(9), ntb_link_disable(9)

memory windows:

• ntb_mw_count(9), ntb_mw_get_align(9), ntb_mw_set_trans(9), ntb_mw_clear_trans(9)
• ntb_peer_mw_count(9), ntb_peer_mw_get_addr(9), ntb_peer_mw_set_trans(9), ntb_peer_mw_clear_trans(9)

doorbells, local side:

• ntb_db_is_unsafe(9), ntb_db_valid_mask(9), ntb_db_vector_count(9), ntb_db_vector_mask(9)
• ntb_db_read(9), ntb_db_set(9), ntb_db_clear(9), ntb_db_read_mask(9), ntb_db_set_mask(9), ntb_db_clear_mask(9)

doorbells, peer side (yes, my girl's whole family):

• ntb_peer_db_addr(9), ntb_peer_db_read(9), ntb_peer_db_clear(9), ntb_peer_db_read_mask(9), ntb_peer_db_set_mask(9), ntb_peer_db_clear_mask(9)

scratchpads:

• ntb_spad_is_unsafe(9), ntb_spad_count(9), ntb_spad_read(9), ntb_spad_write(9)
• ntb_peer_spad_addr(9), ntb_peer_spad_read(9), ntb_peer_spad_write(9)

messages:

• ntb_msg_count(9), ntb_msg_inbits(9), ntb_msg_outbits(9), ntb_msg_read_sts(9), ntb_msg_clear_sts(9), ntb_msg_set_mask(9), ntb_msg_clear_mask(9)
• ntb_msg_read(9), ntb_peer_msg_write(9)

misc icons:

• ntb_get_dma_dev(9), ntb_peer_resource_idx(9), ntb_peer_highest_mw_idx(9)

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and that's the whole page, bestie 🧚 you now know how to ring a peer doorbell and you know the bits you didn't touch stay exactly where they were. iykyk.

<cute>— signed off with love from ./include/linux, dated October 2026, version ntb_peer_db_set(9) · stay slaying 💜🎀</cute>