STRUCT IOMMU_FWSPEC(9)

✨ struct iommu_fwspec(9) ✨

okay so bestie, welcome to the Kernel API Manual — this one's all about struct iommu_fwspec, aka the per-device IOMMU instance data. it's giving "small struct, big responsibilities" tbh 🫶

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🌸 NAME 🌸

struct iommu_fwspec — per-device IOMMU instance data 💅

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🎀 SYNOPSIS 🎀

struct iommu_fwspec {
    struct fwnode_handle    *iommu_fwnode;
    u32 flags;
    unsigned int            num_ids;
    u32 ids[];
 };

like, that's the whole struct. cute, right? four fields and a flex array. iconic. ✨

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🦋 Members 🦋

• iommu_fwnode — the firmware handle for this device's IOMMU. literally the "who's your IOMMU" pointer 🌈
• flags — the IOMMU_FWSPEC_* flags. yes, all of them. iykyk 💫
• num_ids — number of associated device IDs. it's giving headcount 🍓
• ids — the IDs which this device may present to the IOMMU. the whole guest list, basically 🎀

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💜 Description 💜

okay so this is important, no cap: the IDs (and honestly any other information stored in this structure) should be considered private to the IOMMU device driver. they are not to be used directly by IOMMU consumers. 🙈

bestie please do not touch. that data is not yours, it's the driver's. hands off. 💅

like, i cannot stress this enough — the manpage says "and any other information, really," which is such a mood, but fr fr it means everything in there is off-limits to consumers. periodt. 🔥

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🌟 SEE ALSO 🌟

Kernel file ./include/linux/iommu.h, plus this whole squad right here 👑

• struct iommu_fault_page_request(9)
• struct iommu_fault(9)
• enum iommu_page_response_code(9)
• struct iommu_page_response(9)
• struct iopf_queue(9)
• struct iommu_resv_region(9)
• struct iommu_iotlb_gather(9)
• struct iommu_dirty_bitmap(9)
• struct iommu_dirty_ops(9)
• struct iommu_user_data(9)
• struct iommu_user_data_array(9)
• __iommu_copy_struct_from_user(9)
• iommu_copy_struct_from_user(9)
• __iommu_copy_struct_from_user_array(9)
• iommu_copy_struct_from_user_array(9)
• iommu_copy_struct_from_full_user_array(9)
• __iommu_copy_struct_to_user(9)
• iommu_copy_struct_to_user(9)
• struct iommu_ops(9)
• struct iommu_domain_ops(9)
• struct iommu_device(9)
• struct iommu_fault_param(9)
• struct dev_iommu(9)
• iommu_iotlb_gather_is_disjoint(9)
• iommu_iotlb_gather_add_range(9)
• iommu_iotlb_gather_add_page(9)
• struct iommu_sva(9)
• iommu_map_sgtable(9)

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aaaand that's the whole page, bestie, ate and left no crumbs 💖 this lil gem lives over in ./include/linux and the version stamp says October 2026 — so like, future vibes only 🦋✨ mwah, go read your kernel headers responsibly 🧚‍♀️💜