STRUCT PCI_EPC_BAR_DESC(9)

🌸 struct pci_epc_bar_desc(9) 🌸

okay bestie, welcome to the Kernel API Manual page for struct pci_epc_bar_desc — yes it's a whole mouthful, but it's literally just the hardware description for a BAR, and honestly? kind of a baddie for it. 💅

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✨ NAME ✨

struct pci_epc_bar_desc — the hardware description for a BAR. that's it, that's the vibe check, she describes hardware. iconic.

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🎀 SYNOPSIS 🎀

struct pci_epc_bar_desc {
    enum pci_epc_bar_type type;
    u64 fixed_size;
    bool only_64bit;
    u8 nr_rsvd_regions;
    const struct pci_epc_bar_rsvd_region *rsvd_regions;
 };

look at her. five fields. no notes. 🫶

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💖 Members 💖

so, field by field, group-chat style:

• type — the type of the BAR. that's the whole job. which type of BAR it is. simple, elegant, main character energy.
• fixed_size — the fixed size, and heads up: this one only applies if type is BAR_FIXED_MASK. so if the type isn't that, this number is just sitting there not applying. not me pointing that out. 🙈
• only_64bit — if true, an EPF driver is not allowed to choose whether this BAR gets configured as 32-bit or 64-bit — the EPF driver must configure this BAR as 64-bit. no options, no debate, it's giving "the choice was made for you." ⭐
• nr_rsvd_regions — the number of fixed subregions described for BAR_RESERVED. count 'em. 🔥
• rsvd_regions — the fixed subregions behind BAR_RESERVED. yes, plural, yes it's a pointer type in the synopsis, pls stay consistent bestie. 🦋

lowkey reminder: fixed_size is conditional on type being BAR_FIXED_MASK, and only_64bit being true locks out EPF driver choice entirely. those are the two things people mess up, so like... don't. 💀

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🦋 SEE ALSO 🦋

okay the friend group, all of them, going in the exact order they showed up:

• Kernel file ./include/linux/pci-epc.h
• struct pci_epc_map(9)
• enum pci_epc_aux_resource_type(9)
• struct pci_epc_aux_resource(9)
• struct pci_epc_ops(9)
• struct pci_epc_mem_window(9)
• struct pci_epc_mem(9)
• struct pci_epc(9)
• enum pci_epc_bar_type(9)
• enum pci_epc_bar_rsvd_region_type(9)
• struct pci_epc_bar_rsvd_region(9)
• struct pci_epc_features(9)

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and that's the page!! 🎀 sign-off time: this little beauty lives under ./include/linux, dated October 2026, and belongs to the Kernel API Manual — so go forth, read your BAR descs, and slay. periodt. 👑💜