STRUCT TTM_BO_KMAP_OBJ(9)

💅 struct ttm_bo_kmap_obj(9) 💅

okay so this is a page from the Kernel API Manual — yes, the kernel has manuals, and yes, this one is about a struct. a struct, bestie. but she's kind of iconic so stay with me 🫶

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✨ NAME ✨

struct ttm_bo_kmap_obj — (the name line is literally empty in the original, which is so her: no explanation, just vibes. it's the object that describes a kernel mapping of a TTM buffer object, but the manpage refuses to say it in the NAME section. we respect the mystery 💅)

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🌸 SYNOPSIS 🌸

like, the whole shape of her. no cap, here it is exactly:

struct ttm_bo_kmap_obj {
    void *virtual;
    struct page *page;
    enum {
      ttm_bo_map_iomap = 1 | TTM_BO_MAP_IOMEM_MASK,
      ttm_bo_map_vmap = 2,
      ttm_bo_map_kmap = 3,
      ttm_bo_map_premapped = 4 | TTM_BO_MAP_IOMEM_MASK,
    } bo_kmap_type;
    struct ttm_buffer_object *bo;
 };

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🦋 Members 🦋

breaking down the cast of characters, main-character style:

• virtual — the current kernel virtual address. that's it, that's the whole description. she's current, she's virtual, she's addressed. ✨
• page — the page when kmap'ing a single page. one (1) page. single-page energy 🎀
• bo_kmap_type — type of bo_kmap, iykyk. and the options are the enum up in the synopsis: ttm_bo_map_iomap, ttm_bo_map_vmap, ttm_bo_map_kmap, ttm_bo_map_premapped 💖
• bo — the TTM BO. short, sweet, to the point. 🔥

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💜 Description 💜

so here's the lore: this thing is an object describing a kernel mapping. and the reason it has to be flexible is that a TTM bo may live in various memory types with various caching policies — so the mapping can be any one of these four:

• an ioremap
• a vmap
• a kmap
• or part of a premapped region

that's the whole deal. four possible mapping situations, one struct carrying them all. lowkey elegant ngl 🧚

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⭐ SEE ALSO ⭐

go read these next, bestie, the whole friend group:

• Kernel file ./include/drm/ttm/ttm_bo.h
• enum ttm_bo_type(9)
• struct ttm_buffer_object(9)
• struct ttm_operation_ctx(9)
• struct ttm_lru_walk_arg(9)
• struct ttm_lru_walk(9)
• struct ttm_bo_shrink_flags(9)
• ttm_bo_reserve(9)
• ttm_bo_reserve_slowpath(9)
• ttm_bo_move_null(9)
• ttm_bo_unreserve(9)
• ttm_kmap_obj_virtual(9)
• struct ttm_bo_lru_cursor(9)
• ttm_bo_lru_for_each_reserved_guarded(9)

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ngl ttm_bo_lru_for_each_reserved_guarded(9) is giving "I have a long name because I do a lot" and honestly? respect. 👑

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and that's the page!! mwah 💋 this one came from ./include/drm/ttm, dated October 2026, and it's filed under struct ttm_bo_kmap_obj(9) — go off, king 🎀🌈💖