STRUCT I915_TTM_TT(9)

💅 struct i915_ttm_tt(9) — a lil' glow-up

okay so this is a page from the Kernel API Manual (yes, the kernel has a manual, she's that girl) and it's all about struct i915_ttm_tt, bestie. it's a TTM page vector that also carries around some extra private info like a little handbag of secrets 👜✨

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🌸 NAME 🌸

struct i915_ttm_tt — literally a TTM page vector with additional private info tacked on. that's it, that's the vibe.

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✨ SYNOPSIS ✨

look at her, she's so structured:

struct i915_ttm_tt {
    struct ttm_tt ttm;
    struct device *dev;
    struct i915_refct_sgt cached_rsgt;
    bool is_shmem;
    struct file *filp;
 };

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🎀 Members 🎀

• ttm — the base TTM page vector, the main character foundation everything else sits on 💅
• dev — the struct device that gets used for dma mapping and unmapping, she's the one doing the actual DMA-ing 🫶
• cached_rsgt — the cached scatter-gather table. stored and ready, no cap 🌸
• is_shmem — a bool that's set if we're using shmem ✨
• filp — the shmem file, but only if you're on the shmem backend, iykyk 👑

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🦋 Description 🦋

okay this is the important part, listen up 📢

so here's the thing: DMA may be going on right up to the point where the page-vector is unpopulated in delayed destroy. like, literally up until the last second 😭 so that means you keep the scatter-gather table mapped and cached up to that point. don't let it go early, she's still working!

and this is different from the cached gem object io scatter-gather table — that one doesn't have an associated dma mapping. so don't go mixing them up, bestie, they are not the same thing 🙈

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💜 SEE ALSO 💜

• Kernel file: ./drivers/gpu/drm/i915/gem/i915_gem_ttm.c
• i915_ttm_sys_placement(9)
• i915_ttm_free_cached_io_rsgt(9)
• i915_ttm_purge(9)
• i915_ttm_resource_get_st(9)
• i915_ttm_resource_mappable(9)
• i915_ttm_driver(9)
• Migration vs eviction(9)
• i915_ttm_adjust_lru(9)

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go read the whole friend group, they all slay in their own way 💖

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and that's a wrap, bestie! 🎬 this page came out of ./drivers/gpu/drm/i915/gem in October 2026, and yes she's filed under struct i915_ttm_tt(9) — iconic, no notes 👑🌈