epf_ntb_alloc_peer_mem(9)

✨ epf_ntb_alloc_peer_mem(9) ✨

okay so this is a page straight out of the Kernel API Manual (epf_ntb_alloc_peer_mem(9), yes the whole name is the flex) and it's all about grabbing memory inside the peer's outbound address space 🫶 stay with me bestie, it's giving PCI endpoint realness.

---

💖 NAME 💖

epf_ntb_alloc_peer_mem — allocate memory in the peer's outbound address space. that's it, that's the whole vibe ✨

---

🦋 SYNOPSIS 🦋

int epf_ntb_alloc_peer_mem (struct device *dev , struct epf_ntb_epc
*ntb_epc , enum epf_ntb_bar bar , struct epf_ntb_epc *peer_ntb_epc ,
size_t size );

---

🎀 ARGUMENTS 🎀

• dev — the PCI device. the main character of this whole call, lowkey 💅
• ntb_epc — the EPC associated with one of the HOST whose BAR holds peer's outbound address. yes it's a mouthful, no we're not skipping it 🙈
• bar — the BAR of ntb_epc in for which memory has to be allocated (could be BAR_DB_MW1, BAR_MW2, BAR_MW3, BAR_MW4) — pick your fighter ⭐
• peer_ntb_epc — the EPC associated with HOST whose outbound address space is used by ntb_epc. that's the peer, that's who we're shopping for 🛍️
• size — the size of the address region that has to be allocated in peers OB SPACE. no cap, size matters here 🔥

---

🌸 DESCRIPTION 🌸

okay bestie, the manpage hits you with the diagram first, so here it is in all its chaotic glory 👑 (yes it is exactly this, we do not edit art):

       ┌─────────────────────────────────────────────────────────────┐
       │ BAR0           Doorbell 1   +-----------> MSI   X ADDRESS 1 │
       │ BAR1           Doorbell 2   +---------+                     │
       └─────────────────────────────────────────────────────────────┘
       |       BAR2      |          |   Doorbell 3   +-------+ |
       +-----------------+ |       BAR3      |    |     |   Doorbell 4
       +-----+ |   +-----------------+ |       BAR4      |    |     |
       |     | |   +-----------------+ |       BAR5      |    |     |
       |   | |     +-----------------+ EP CONTROLLER 1            |
       |   | |     +-----------------+ |                |   | +---->+ MSI|X
       ADDRESS 4 | (A)      EP CONTROLLER 2     |       |                 | (OB
       SPACE)        |       |                 | +------->      MW1        | |
       | |                 | (B)     +-----------------+ |                 | |
       | |                 | |                 | |                 | PCI
       Address Space (Managed by HOST2)

so what are we actually doing? we're allocating memory in the OB space of EP CONTROLLER 2 in the diagram above ⬆️ literally that controller, that space.

and we allocate for Doorbell 1, Doorbell 2, Doorbell 3, Doorbell 4, MW1 (and MW2, MW3, MW4) — the whole squad, nobody gets left out 💜

---

🌈 SEE ALSO 🌈

the kernel file, iykyk:

• Kernel file ./drivers/pci/endpoint/functions/pci-epf-ntb.c

and the entire friend group (all 32 of them, we're not cutting anybody, periodt):

• epf_ntb_link_up(9)
• epf_ntb_configure_mw(9)
• epf_ntb_teardown_mw(9)
• epf_ntb_configure_msi(9)
• epf_ntb_configure_msix(9)
• epf_ntb_configure_db(9)
• epf_ntb_teardown_db(9)
• epf_ntb_cmd_handler(9)
• epf_ntb_peer_spad_bar_clear(9)
• epf_ntb_peer_spad_bar_set(9)
• epf_ntb_config_sspad_bar_clear(9)
• epf_ntb_config_sspad_bar_set(9)
• epf_ntb_config_spad_bar_free(9)
• epf_ntb_config_spad_bar_alloc(9)
• epf_ntb_config_spad_bar_alloc_interface(9)
• epf_ntb_free_peer_mem(9)
• epf_ntb_db_mw_bar_clear(9)
• epf_ntb_db_mw_bar_cleanup(9)
• epf_ntb_configure_interrupt(9)
• epf_ntb_db_mw_bar_init(9)
• epf_ntb_epc_create_interface(9)
• epf_ntb_epc_create(9)
• epf_ntb_init_epc_bar_interface(9)
• epf_ntb_init_epc_bar(9)
• epf_ntb_epc_init_interface(9)
• epf_ntb_epc_cleanup_interface(9)
• epf_ntb_epc_cleanup(9)
• epf_ntb_epc_init(9)
• epf_ntb_bind(9)
• epf_ntb_unbind(9)
• epf_ntb_add_cfs(9)
• epf_ntb_probe(9)

---

okay that's the whole page, you ate that 🍓 mwah 💋

sign-off time: this gorgeous little page lives in ./drivers/pci/endpoint/functions, dated October 2026, and it's filed under epf_ntb_alloc_peer_mem(9) — go forth and allocate, bestie 🧚💖