blk_rq_dma_map_iter_next(9)

💫 blk_rq_dma_map_iter_next(9) — the kernel API manual page, bestie edition 💫

okay so this is a section 9 (kernel API) manual page for blk_rq_dma_map_iter_next, and honestly? it's giving "small function, big job." let's get into it 🎀

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✨ NAME ✨

blk_rq_dma_map_iter_next — map the next DMA segment for a request

like, literally what it says on the tin, no cap 💅

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🌸 SYNOPSIS 🌸

bool blk_rq_dma_map_iter_next (struct request *req , struct device
*dma_dev , struct blk_dma_iter *iter );

she takes three things and hands you back a bool. iconic signature tbh 🫶

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🦋 ARGUMENTS 🦋

• req — the request you wanna map. yes, that request. the one right in front of you 💖
• dma_dev — the device you're mapping to. pick your fave, she's not judging ✨
• iter — the block layer DMA iterator. the little main character holding all your state 🎀

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🔥 DESCRIPTION 🔥

so basically: this is the "and then what?" of the DMA mapping saga. you call blk_rq_dma_map_iter_start first, and then this function iterates you along to the next mapping. if you want the full breakdown of the arguments, the manpage says to go check out blk_rq_dma_map_iter_start — see there for a detailed description of the arguments. iykyk 💅

she returns false if there's no segment to map, and that includes when it happened because of an error 😭. she returns true if it did, in fact, map a segment. slay.

now the tea on what comes back 🍓:

• if a segment was mapped → the DMA address for it lands in iter.addr, and the length lands in iter.len. go off, queen 👑
• if no segment was mapped → the status code comes back to you in iter.status. that's your vibe check, read it carefully ⭐

ngl bestie, always peek at iter.status when you get a false — that's where the actual story is 🙈

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🌈 SEE ALSO 🌈

the kernel file ./block/blk-mq-dma.c, plus the whole friend group of related calls — go say hi 💜:

• blk_rq_dma_map_iter_start(9)
• blk_rq_integrity_dma_map_iter_start(9)
• blk_rq_integrity_dma_map_iter_next(9)
• blk_rq_map_integrity_sg(9)

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and that's the whole page, bestie 💖 this one lives under ./block in the source tree, and it's stamped October 2026 in the kernel API manual. go map some segments, you absolute icon 🌸🦋✨