swiotlb_search_area(9)

💫 swiotlb_search_area(9) 💫

okay so this is a page from the Kernel API Manual and honestly? it's a little baddie. it's called swiotlb_search_area and its whole personality is searching one memory area in all pools. one area. all pools. she's thorough. 💅

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✨ SYNOPSIS ✨

int swiotlb_search_area (struct device *dev , int start_cpu , int
cpu_offset , phys_addr_t orig_addr , size_t alloc_size , unsigned int
alloc_align_mask , struct io_tlb_pool **retpool );

seven arguments bestie. seven. she's high-maintenance but she's worth it 🎀

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🌸 ARGUMENTS 🌸

• dev — the device that's mapping the buffer. it's giving "who do you belong to" energy.
• start_cpu — the CPU number you're starting from. your little launchpad 🚀
• cpu_offset — how far you're offset from start_cpu. yes it's relative, yes it matters.
• orig_addr — the original (non-bounced) IO buffer address. the real one, before the bounce glow-up ✨
• alloc_size — total requested size of the bounce buffer, including the initial alignment padding. don't forget the padding, she counts it, fr fr.
• alloc_align_mask — the required alignment of the allocated buffer. the vibe check for where things can sit 🦋
• retpool — the used memory pool, updated on return. she writes back to you, that's the whole point 💖

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🔥 DESCRIPTION 🔥

so what does she actually do? she searches one memory area across all pools, hunting for a sequence of slots that match the allocation constraints. that's it. that's the whole job. no cap. 👑

like, imagine you need a run of slots that fit certain rules, and you're checking one specific area in every pool until something matches. iconic behavior honestly. 🌈

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🎀 RETURN 🎀

• the index of the first allocated slot — slay, you found one 🫶
• or -1 on error — not slay, something went wrong 😭

heads up bestie: -1 is the failure signal here, so don't go treating it like a valid index. that would be a bad time. 💀

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🦋 SEE ALSO 🦋

Kernel file ./kernel/dma/swiotlb.c, plus the whole friend group: struct io_tlb_slot(9), struct io_tlb_area(9), swiotlb_adjust_nareas(9), limit_nareas(9), add_mem_pool(9), alloc_dma_pages(9), swiotlb_alloc_tlb(9), swiotlb_free_tlb(9), swiotlb_alloc_pool(9), swiotlb_dyn_alloc(9), __swiotlb_find_pool(9), swiotlb_del_pool(9), swiotlb_dev_init(9), swiotlb_align_offset(9), swiotlb_search_pool_area(9), swiotlb_find_slots(9), mem_pool_used(9), mem_used(9), swiotlb_tbl_map_single(9), swiotlb_del_transient(9), is_swiotlb_allocated(9), default_swiotlb_base(9), default_swiotlb_limit(9). go read them, they're literally all right there 💜

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okay and for the cute sign-off: this little masterpiece lives in ./kernel/dma and it's stamped October 2026. future-coded of her. see you in the pools bestie 🧚‍♀️⭐🍓