STRUCT RISCV_IOMMU_DC(9)

✨ struct riscv_iommu_dc(9) ✨

okay bestie, welcome to the Kernel API Manual — this is the page for struct riscv_iommu_dc(9), and yes it's giving "tiny struct, big responsibilities" energy 💅

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🎀 NAME 🎀

struct riscv_iommu_dc — the Device Context 🫶 literally what it says on the tin.

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🌸 SYNOPSIS 🌸

struct riscv_iommu_dc {
    u64 tc;
    u64 iohgatp;
    u64 ta;
    u64 fsc;
    u64 msiptp;
    u64 msi_addr_mask;
    u64 msi_addr_pattern;
    u64 _reserved;
 };

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💖 Members 💖

girl, let's go field by field, no skipping, we do not skip in this house 👑

• tc — Translation Control 🔥
• iohgatp — I/O Hypervisor guest address translation and protection (that's the Second stage context, iykyk) ✨
• ta — Translation Attributes 🎀
• fsc — First stage context 💜
• msiptp — MSI page table pointer 🌸
• msi_addr_mask — MSI address mask 🌈
• msi_addr_pattern — MSI address pattern ⭐
• _reserved — Reserved for future use, padding 🦋 (sitting there being mysterious, we respect it)

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🧚 Description 🧚

so this struct is what the leaf nodes on the Device Directory Table use, fr fr. main character energy of the DDT 🥰

but here's the plot twist 😭 — in case RISCV_IOMMU_CAPABILITIES_MSI_FLAT is not set, the bottom 4 fields are not present and are skipped with pointer arithmetic to avoid casting. yep, pointer arithmetic, we love a clever little workaround. you can check out riscv_iommu_get_dc if you wanna see it in action 💫

💡 also: see section 2.1 for more details — the og docs said it, we're saying it.

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👀 SEE ALSO 👀

Kernel file ./drivers/iommu/riscv/iommu-bits.h enum 🔍 and the whole friend group:

• riscv_iommu_igs_settings(9)
• enum riscv_iommu_ddtp_modes(9)
• enum riscv_iommu_hpmevent_id(9)
• enum riscv_iommu_dc_iohgatp_modes(9)
• enum riscv_iommu_dc_fsc_atp_modes(9)
• struct riscv_iommu_pc(9)
• struct riscv_iommu_command(9)
• struct riscv_iommu_fq_record(9)
• enum riscv_iommu_fq_causes(9)
• enum riscv_iommu_fq_ttypes(9)
• struct riscv_iommu_pq_record(9)
• struct riscv_iommu_msipte(9)

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and that's the whole page bestie, you ate that 🍓 mwah 💋

source: ./drivers/iommu/riscv 🌸 date: October 2026 🌸 struct riscv_iommu_dc(9) — slay, go read some iommu code now 👑✨