STRUCT TB_DMA_PORT(9)

👑 struct tb_dma_port(9) — the DMA control port, bestie

okay so this is a page from the Kernel API Manual (yes, the kernel has lore, and yes, we're gonna get into it ✨). This one's all about struct tb_dma_port, which is literally the DMA control port. It's giving small-but-mighty. It's giving "I hold the mailbox regs and I know it." 💅

---

✨ SYNOPSIS ✨

here's the whole entire vibe, copy-pasted with love, no cap:

struct tb_dma_port {
    struct tb_switch *sw;
    u8 port;
    u32 base;
    u8 buf[];
};

like… four fields and one flexible array. iconic behavior honestly 🎀

---

🌸 Members 🌸

get comfy, we're meeting the squad one by one 🫶

• sw — the struct tb_switch that this DMA port belongs to. it's the whole reason we're here, the main character energy of the group 💖
• port — a u8, the switch port number where the DMA capability is found. this is where the fun stuff lives, iykyk 🔥
• base — a u32, the start offset of the mailbox registers. so like, that's where the mailbox begins. don't lose it 🙈
• buf — a u8 flexible array, a temporary buffer to store a single block. one block. singular. it's doing its best and honestly? slay 💅

ngl, buf[] being an empty-looking array at the end is the classic "trailing flexible array member" situation — it's literally just declared as u8 buf[]; and that's all the original says about it, so we're not gonna start making stuff up 👑

---

👑 SEE ALSO 👑

go read the source, bestie, it's all right here — the kernel file ./drivers/thunderbolt/dma_port.c plus the whole friend group:

• dma_port_alloc(9)
• dma_port_free(9)
• dma_port_flash_read(9)
• dma_port_flash_write(9)
• dma_port_flash_update_auth(9)
• dma_port_flash_update_auth_status(9)
• dma_port_power_cycle(9)

fr fr, that's the whole crew 🌈

---

and that's the page!! 🦋 drop a 💖 for ./drivers/thunderbolt (that's where this all lives) and for October 2026, the date this little legend was stamped. okay bye, go read about DMA ports, ily 😭🌸