STRUCT CDX_DEVICE(9)

💅 NAME

struct cdx_device — the CDX device object, aka the whole entire main character of this page 🫶

So this is a thing from the Linux kernel API manual, bestie. It's struct cdx_device(9), and we're about to go through it field by field, no skipping, no cap. Grab a snack. 🍓

✨ SYNOPSIS

struct cdx_device {
    struct device dev;
    struct cdx_controller *cdx;
    u16 vendor;
    u16 device;
    u16 subsystem_vendor;
    u16 subsystem_device;
    u32 class;
    u8 revision;
    u8 bus_num;
    u8 dev_num;
    struct resource res[MAX_CDX_DEV_RESOURCES];
    struct bin_attribute *res_attr[MAX_CDX_DEV_RESOURCES];
    struct dentry *debugfs_dir;
    u8 res_count;
    u64 dma_mask;
    u16 flags;
    u32 req_id;
    bool is_bus;
    bool enabled;
    u32 msi_dev_id;
    u32 num_msi;
    struct mutex irqchip_lock;
    bool msi_write_pending;
 };

Like… look at her. Twenty-something fields and every single one of them matters. Obsessed. 💖

🎀 Members

Okay so this is the part where we go one by one, and I mean one by one. No field left behind. 🌈

• dev — the Linux driver model device object. the lil' foundation of it all, lowkey iconic.
• cdx — the CDX controller that's associated with this device. her handler, her person, iykyk.
• vendor — the Vendor ID for the CDX device.
• device — the Device ID for the CDX device.
• subsystem_vendor — the Subsystem Vendor ID for the CDX device.
• subsystem_device — the Subsystem Device ID for the CDX device.
• class — the Class for the CDX device.
• revision — the Revision of the CDX device.
• bus_num — the Bus number for this CDX device.
• dev_num — the Device number for this device.
• res — an array of MMIO region entries. not one, an array, periodt.
• res_attr — the resource binary attribute.
• debugfs_dir — the debugfs directory for this device. peek inside, it's giving behind-the-scenes 🦋
• res_count — the number of valid MMIO regions.
• dma_mask — the Default DMA mask.
• flags — CDX device flags.
• req_id — the Requestor ID associated with the CDX device.
• is_bus — is this bus device. a yes/no situation, very demure.
• enabled — is this bus enabled.
• msi_dev_id — the MSI Device ID associated with the CDX device.
• num_msi — the Number of MSI's supported by the device.
• irqchip_lock — a lock to synchronize irq/msi configuration. mutual exclusion but make it ✨self-care✨
• msi_write_pending — MSI write pending for this device.

Ngl bestie, don't go poking at these fields arbitrarily — the manpage spells out what each one is, and that's the whole story. 💅

🦋 SEE ALSO

Run, don't walk, to these:

• Kernel file ./include/linux/cdx/cdx_bus.h — the source of truth, literally.
• CDX_DEVICE(9)
• CDX_DEVICE_DRIVER_OVERRIDE(9)
• struct cdx_ops(9)
• struct cdx_controller(9)
• struct cdx_driver(9)
• __cdx_driver_register(9)
• cdx_driver_unregister(9)
• cdx_dev_reset(9)
• cdx_set_master(9)
• cdx_clear_master(9)
• cdx_enable_msi(9)
• cdx_disable_msi(9)

aaaand that's the whole page, bestie 🥹💜 this baby lives in ./include/linux/cdx, and this particular glow-up is dated October 2026 — so if you're reading it after that, hi from the past, slay, hope the kernel still compiles. 🎀✨