STRUCT DRM_DEVICE(9)

💖 struct drm_device — NAME ✨

Okay bestie, so struct drm_device(9) is the DRM device structure — the whole big-deal data structure for a DRM card. This page lives in the Kernel API Manual and honestly it's giving "backstage pass to the graphics stack" energy. Let's get into it 💅

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🌸 SYNOPSIS 🌸

struct drm_device {
    int if_version;
    struct kref ref;
    struct device *dev;
    struct device *dma_dev;
    struct {
      struct list_head resources;
      void *final_kfree;
      spinlock_t lock;
    } managed;
    const struct drm_driver *driver;
    void *dev_private;
    struct drm_minor *primary;
    struct drm_minor *render;
    struct drm_minor *accel;
    bool registered;
    struct drm_master *master;
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE;
    struct vfsmount *huge_mnt;
  #endif;
    u32 driver_features;
    bool unplugged;
    struct inode *anon_inode;
    char *unique;
    struct mutex master_mutex;
    atomic_t open_count;
    struct mutex filelist_mutex;
    struct list_head filelist;
    struct list_head filelist_internal;
    struct mutex clientlist_mutex;
    struct list_head clientlist;
    struct list_head client_sysrq_list;
    bool vblank_disable_immediate;
    struct drm_vblank_crtc *vblank;
    spinlock_t vblank_time_lock;
    spinlock_t vbl_lock;
    u32 max_vblank_count;
    struct list_head vblank_event_list;
    spinlock_t event_lock;
    unsigned int num_crtcs;
    struct drm_mode_config mode_config;
    struct mutex object_name_lock;
    struct idr object_name_idr;
    struct drm_vma_offset_manager *vma_offset_manager;
    struct drm_vram_mm *vram_mm;
    enum switch_power_state switch_power_state;
    struct drm_fb_helper *fb_helper;
    struct dentry *debugfs_root;
    struct mutex gem_lru_mutex;
};

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🎀 Members 🎀

Time for the member-by-member tour, bestie. Grab a snack 🍓

• if_version — the highest interface version that's been set.
• ref — the object ref-count. Classic refcount moment.
• dev — the device structure of the bus-device.
• dma_dev — the device used for DMA operations. Lowkey only required if the device dev cannot do DMA by itself, and it should be NULL otherwise. Call drm_dev_dma_dev to get the DMA device instead of touching this field directly, and call drm_dev_set_dma_dev to set it.

So like, DRM devices are sometimes bound to virtual devices that can't perform DMA on their own — drivers should point this field at the respective DMA controller. 😌

Devices on USB and other peripheral busses also can't perform DMA by themselves, so dma_dev should point at the bus controller that does DMA on behalf of such a device. Required for importing buffers via dma-buf. 🦋

If it's set, the DRM core automatically releases the reference on the device. No cap.

• managed — managed resources, linked to the lifetime of this drm_device as tracked by ref.
  • managed.resources — the managed resources list.
  • managed.final_kfree — pointer for the final kfree call.
  • managed.lock — protects managed.resources.
• driver — the DRM driver managing the device.
• dev_private — DRM driver private data. This is deprecated and should be left set to NULL. 🚩

Instead of using this pointer, it's recommended that drivers use devm_drm_dev_alloc and embed struct drm_device in their larger per-device structure. That's the move, fr fr.

• primary — the Primary node. Drivers should not interact with this directly. debugfs interfaces can be registered with drm_debugfs_add_file, and sysfs should be directly added on the hardware (and not the character device node) struct device dev.
• render — the Render node. Drivers should not interact with this directly, ever. Drivers should not expose any additional interfaces in debugfs or sysfs on this node. Like, at all. 💀
• accel — the Compute Acceleration node.
• registered — internally used by drm_dev_register and drm_connector_register.
• master — the currently active master for this device. Protected by master_mutex.
• huge_mnt — huge tmpfs mountpoint used at GEM object initialization drm_gem_object_init. Drivers can call drm_gem_huge_mnt_create to create, mount and use it. The default tmpfs mountpoint (shm_mnt) is used if NULL.
• driver_features — per-device driver features.

Drivers can clear specific flags here to disallow certain features on a per-device basis while still sharing a single struct drm_driver instance across all devices. Obsessed with the efficiency tbh ✨

• unplugged — flag to tell if the device has been unplugged. See drm_dev_enter and drm_dev_is_unplugged.
• anon_inode — inode for the private address-space.
• unique — unique name of the device.
• master_mutex — lock for drm_minor.master and drm_file.is_master.
• open_count — usage counter for outstanding files open, protected by drm_global_mutex.
• filelist_mutex — protects filelist.
• filelist — list of userspace clients, linked through drm_file.lhead.
• filelist_internal — list of open DRM files for in-kernel clients. Protected by filelist_mutex.
• clientlist_mutex — protects clientlist access.
• clientlist — list of in-kernel clients. Protected by clientlist_mutex.
• client_sysrq_list — entry into the list of devices registered for sysrq. Allows in-kernel clients on this device to handle sysrq keys.
• vblank_disable_immediate — if true, the vblank interrupt will be disabled immediately when the refcount drops to zero, instead of via the vblank disable timer.

This can be set to true if the hardware has a working vblank counter with high-precision timestamping (otherwise there are races 😭) and the driver uses drm_crtc_vblank_on and drm_crtc_vblank_off appropriately. Also, see max_vblank_count, drm_crtc_funcs.get_vblank_counter and drm_vblank_crtc_config.disable_immediate.

• vblank — array of vblank tracking structures, one per struct drm_crtc. For historical reasons (vblank support predates kernel modesetting) this is free-standing and not part of struct drm_crtc itself. It must be initialized explicitly by calling drm_vblank_init.
• vblank_time_lock — protects vblank count and time updates during vblank enable/disable.
• vbl_lock — top-level vblank references lock, wraps the low-level vblank_time_lock.
• max_vblank_count — maximum value of the vblank registers. This value +1 will result in a wrap-around of the vblank register. It's used by the vblank core to handle wrap-arounds.

If set to zero, the vblank core will try to guess the elapsed vblanks between times when the vblank interrupt is disabled, using high-precision timestamps. That approach is suffering from small races and imprecision over longer time periods, hence exposing a hardware vblank counter is always recommended. 👑

This is the statically configured device-wide maximum. The driver can instead choose to use a runtime configurable per-crtc value drm_vblank_crtc.max_vblank_count, in which case max_vblank_count must be left at zero. See drm_crtc_set_max_vblank_count on how to use the per-crtc value.

If non-zero, drm_crtc_funcs.get_vblank_counter must be set.

• vblank_event_list — list of vblank events.
• event_lock — protects vblank_event_list and event delivery in general. See drm_send_event and drm_send_event_locked.
• num_crtcs — number of CRTCs on this device.
• mode_config — current mode config.
• object_name_lock — GEM information.
• object_name_idr — GEM information.
• vma_offset_manager — GEM information.
• vram_mm — VRAM MM memory manager.
• switch_power_state — power state of the client. Used by drivers supporting the switcheroo driver. The state is maintained in the vga_switcheroo_client_ops.set_gpu_state callback.
• fb_helper — pointer to the fbdev emulation structure. Set by drm_fb_helper_init and cleared by drm_fb_helper_fini.
• debugfs_root — root directory for debugfs files.
• gem_lru_mutex — lock protecting movement of GEM objects between LRUs.

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🦋 Description 🦋

This structure represents a complete card that may contain multiple heads. Main character energy, honestly 🫶

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⭐ SEE ALSO ⭐

Kernel file ./include/drm/drm_device.h — plus struct drm_wedge_task_info(9), enum switch_power_state(9), drm_dev_dma_dev(9). Go read those too, bestie, iykyk 💜

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That's the whole vibe check! Source path ./include/drm, dated October 2026, from the Kernel API Manual. Slay, go forth and initialize your vblanks correctly 💅✨🎀