read_mod_write(9)

💅 read_mod_write(9) — like, the kernel API manual page, bestie 🎀

Okay so this is read_mod_write, straight out of the 9 section of the manual — kernel API territory, iykyk. Buckle up, it's a short one but she's important. ✨

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🌸 NAME 🌸

read_mod_write — the way we calculate the IRQ register index and set/clear the bits. That's literally the whole job description. No cap. 💅

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🦋 SYNOPSIS 🦋

void read_mod_write (struct hfi1_devdata *dd , u16 src , u64 bits , bool
set );

That's it. That's the whole signature. She's void, she's got four args, she's doing her thing. 🔥

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✨ ARGUMENTS ✨

• dd — a valid devdata, bestie. Valid. Don't be coming at her with your invalid devdata, she will not be having it 🙈
• src — the IRQ source, which is literally what we use to determine the register index from. Like, it's giving "lookup key" energy. 🔑
• bits — the bits that get set or get cleared. Whichever one you're on. Those bits. 💖
• set — true == set the bits, false == clear the bits. Iconic boolean behaviour, truly the main character of this function ngl ⭐

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💜 SEE ALSO 💜

Okay so first up, the kernel file herself:

• Kernel file ./drivers/infiniband/hw/hfi1/chip.c

And then the whole friend group, like the entire extended squad, all of them, no one left out 🫶:

• hfi1_addr_from_offset(9)
• read_csr(9)
• write_csr(9)
• get_csr_addr(9)
• update_xmit_counters(9)
• apply_link_downgrade_policy(9)
• is_rcv_avail_int(9)
• is_rcv_urgent_int(9)
• general_interrupt(9)
• hfi1_rcd_eoi_intr(9)
• hfi1_netdev_rx_napi(9)
• data_vls_operational(9)
• encode_rcv_header_entry_size(9)
• hfi1_validate_rcvhdrcnt(9)
• set_hdrq_regs(9)
• update_statusp(9)
• wait_logical_linkstate(9)
• set_intr_bits(9)
• set_up_interrupts(9)
• hfi1_get_qp_map(9)
• init_qpmap_table(9)
• init_qos(9)
• hfi1_init_dd(9)
• create_pbc(9)

Literally the whole chip.c friend group, go say hi to all of them 💀

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Lowkey a vibe check reminder: this page is read_mod_write(9) from the kernel API manual, and everything above is the whole page — no deleted sections, no cut lore, she's complete. 🧚

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Mwah, that's a wrap bestie 💋 — this one comes to you from ./drivers/infiniband/hw/hfi1, dated October 2026, and it ate, periodt. 🌈