pbus_size_io(9)

pbus_size_io(9) 💅

okay so bestie, we're in the Kernel API Manual and this is pbus_size_io(9) — the function that sizes the I/O window of a given bus. 🫶

🌸 NAME 🌸

pbus_size_io — Size the I/O window of a given bus. ✨

✨ SYNOPSIS ✨

void pbus_size_io (struct pci_bus *bus , resource_size_t add_size ,
       struct list_head *realloc_head );

🎀 ARGUMENTS 🎀

• bus — the bus. 🚌
• add_size — additional I/O window. ➕
• realloc_head — track the additional I/O window on this list. 📝

🦋 DESCRIPTION 🦋

okay so sizing the I/O windows of the PCI-PCI bridge is literally trivial, because those windows have 1K or 4K granularity, and the I/O ranges of non-bridge PCI devices are limited to 256 bytes. 💅

⚠️ but we absolutely must be careful with the ISA aliasing though — that's the one that can sneak up on you. 😭

🌈 SEE ALSO 🌈

Kernel file ./drivers/pci/setup-bus.c is right there, and you also gotta peek at these:

• pci_dev_res_add_to_list(9)
• pbus_select_window_for_type(9)
• pbus_select_window(9)
• reassign_resources_sorted(9)
• assign_requested_resources_sorted(9)
• pbus_size_mem(9)

xoxo bestie 💖 — signed from source/version ./drivers/pci, dated October 2026, and this whole page is literally pbus_size_io(9). periodt. 👑