vmbus_allocate_mmio(9)

💅 vmbus_allocate_mmio(9)

okay so bestie, this is a page from the Kernel API Manual and it's all about vmbus_allocate_mmio — Pick a memory-mapped I/O range. yep that's literally the whole vibe. it's the function that goes "here, have an MMIO window, slay" 🎀

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✨ SYNOPSIS ✨

int vmbus_allocate_mmio (struct resource **new , struct hv_device
*device_obj , resource_size_t min , resource_size_t max ,
resource_size_t size , resource_size_t align , bool fb_overlap_ok );

it returns an int, and yes the whole thing is one long signature so hydrate before reading it 💧

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🌸 ARGUMENTS 🌸

• new — if it works out, you get a pointer to the allocated MMIO space dropped in here. a little gift 🎁
• device_obj — this is how the caller identifies itself. like showing your student ID at the door ngl
• min — minimum guest physical address of the allocation
• max — maximum guest physical address
• size — size of the range to be allocated
• align — alignment of the range to be allocated
• fb_overlap_ok — whether this allocation can be allowed to overlap the video frame buffer. yes the frame buffer, the whole "your screen" situation 👀

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🦋 DESCRIPTION 🦋

so the way this works: the function walks the resources granted to VMBus by the _CRS object in the ACPI namespace, underneath the parent "bridge" — whether that's a root PCI bus in the Generation 1 case, or a Module Device in the Generation 2 case. two eras, same energy ✨

then it attempts to allocate from the global MMIO pool in a way that matches the constraints supplied in these parameters and by that _CRS. so like, the parameters say what you want, and _CRS says what's actually allowed. compromise, communication, it's giving healthy relationship 💖

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👑 RETURN 👑

0 on success, -errno on failure. no cap, that's it.

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🔥 SEE ALSO 🔥

• Kernel file ./drivers/hv/vmbus_drv.c
• __vmbus_driver_register(9)
• vmbus_driver_unregister(9)
• hv_create_ring_sysfs(9)
• hv_remove_ring_sysfs(9)
• vmbus_free_mmio(9)

all the sibling functions, the whole friendgroup fr fr 🫶

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anyway that's the tea — this page lives in ./drivers/hv and it's dated October 2026, so mark your calendars bestie 💅✨