STRUCT MSI_DESC(9)

🌸 NAME 🌸

okay bestie, you're on the struct msi_desc(9) page from the Kernel API Manual, and the name is literally Descriptor structure for MSI based interrupts. That's the assignment 💅

✨ SYNOPSIS ✨

Here's the whole struct, every line, no cap:

       struct msi_desc {
           unsigned int                    irq;
           unsigned int                    nvec_used;
           struct device                   *dev;
           struct msi_msg                  msg;
           struct irq_affinity_desc        *affinity;
         #ifdef CONFIG_IRQ_MSI_IOMMU;
           u64 iommu_msi_iova : 58;
           u64 iommu_msi_shift : 6;
         #endif;
         #ifdef CONFIG_SYSFS;
           struct device_attribute         *sysfs_attrs;
         #endif;
           void (*write_msi_msg)(struct msi_desc *entry, void *data);
           void *write_msi_msg_data;
           u16 msi_index;
           union {
             struct pci_msi_desc     pci;
             struct msi_desc_data    data;
           };
        };

🎀 Members 🎀

Every member, bestie — yes, all of them, including the anonymous-union moment 🫶

• irq — The base interrupt number.
• nvec_used — The number of vectors used.
• dev — Pointer to the device which uses this descriptor.
• msg — The last set MSI message cached for reuse.
• affinity — Optional pointer to a cpu affinity mask for this descriptor.
• iommu_msi_iova — Optional shifted IOVA from the IOMMU to override the msi_addr. Only used if iommu_msi_shift != 0.
• iommu_msi_shift — Indicates how many bits of the original address should be preserved when using iommu_msi_iova.
• sysfs_attrs — Pointer to sysfs device attribute.
• write_msi_msg — Callback that may be called when the MSI message address or data changes.
• write_msi_msg_data — Data parameter for the callback.
• msi_index — Index of the msi descriptor.
• {unnamed_union} — anonymous.
• pci — PCI specific msi descriptor data.
• data — Generic MSI descriptor data.

🦋 SEE ALSO 🦋

The page points you at Kernel file ./include/linux/msi.h, and the cross-refs are giving linked-list energy:

• struct msi_msg(9)
• struct pci_msi_desc(9)
• union msi_domain_cookie(9)
• struct msi_desc_data(9)
• struct msi_dev_domain(9)
• msi_first_desc(9)
• msi_domain_for_each_desc(9)
• msi_for_each_desc(9)
• msi_msg_set_addr(9)
• msi_insert_msi_desc(9)
• msi_free_msi_descs_range(9)
• msi_free_msi_descs(9)
• struct msi_domain_ops(9)
• struct msi_domain_info(9)
• struct msi_domain_template(9)
• struct msi_parent_ops(9)

that's the whole page, bestie — slay 💖 It comes from ./include/linux, dated October 2026, and it's the struct msi_desc(9) page. periodt.