pci_mmap_legacy_io(9)

💖 pci_mmap_legacy_io(9) — like, the Kernel API Manual, bestie ✨

okay so picture this: it's the kernel API manual, it's giving very much "documentation that actually slaps," and today's main character is pci_mmap_legacy_io. no cap. let's get into it 🎀

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🌸 NAME 🌸

pci_mmap_legacy_io — maps legacy PCI IO into user memory space, and yes that's the whole vibe 💅

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🦋 SYNOPSIS 🦋

int pci_mmap_legacy_io (struct file *filp , struct kobject *kobj , const
       struct bin_attribute *attr , struct vm_area_struct *vma );

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✨ ARGUMENTS ✨

• filp — the open sysfs file. literally just the file handle, bestie 🫶
• kobj — the kobject corresponding to the device to be mapped. it's the thing telling you which device we're talking about 👑
• attr — the struct bin_attribute for this file. the whole binary-attribute situation for this file, periodt 💜
• vma — the struct vm_area_struct that got passed to mmap. mmap hands you this, you hold onto it 🌈

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🔥 DESCRIPTION 🔥

so the way this works: it uses an arch specific callback, pci_mmap_legacy_io_page_range, to mmap legacy IO space (the first meg of bus space, iykyk) into application virtual memory space. iconic behavior, honestly 🧚

and if the operation isn't supported? it returns -ENOSYS. not me getting "not implemented" energy 😭 at least it's polite about it.

heads up bestie: that first meg of bus space is legacy IO space — the description says exactly what gets mapped, so don't go inventing extra ranges, fr fr 💀

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🌟 SEE ALSO 🌟

Kernel file ./drivers/pci/pci-sysfs.c — go read it, it's the source of truth 🍓

and the whole friend group:

• pci_read_legacy_io(9)
• pci_write_legacy_io(9)
• pci_mmap_legacy_mem(9)
• pci_mmap_resource(9)
• pci_write_rom(9)
• pci_read_rom(9)

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okay that's the whole page, no skips, we ate and left no crumbs 💅✨ this cutie lives in ./drivers/pci and it's dated October 2026 — so yeah, mark your calendar, mwah 💖🎀🦋