min_chan(9)

✨ NAME ✨

Hey bestie, welcome to the min_chan(9) manual 💖 — yes, min_chan(9), the one and only. It finds the channel with min count and in the same NUMA-node as the CPU. That's the whole assignment, and it ate. 💅

🦋 SYNOPSIS 🦋

struct dma_chan * min_chan (enum dma_transaction_type cap , int cpu );

🌸 ARGUMENTS 🌸

• cap — the capability to match, aka the specific vibe the channel has to have. ✨
• cpu — the CPU index which the channel should be close to. Think "near this CPU, please." 🫶

💖 DESCRIPTION 💖

Okay so here's the situation: if some channels are close to the given CPU, the one with the lowest reference count is returned. That's the main character pick. 👑

Otherwise? The CPU is ignored, and only the reference count is taken into account. Not me ignoring the CPU — it's literally what the function does 😭. Lowkey simple, highkey important, iykyk.

🚨 Lock check, bestie: this must be called under dma_list_mutex. Like, dma_list_mutex is not a suggestion. Do not skip it. Periodt.

🔥 SEE ALSO 🔥

Kernel file ./drivers/dma/dmaengine.c — plus the whole squad (iykyk): dev_to_dma_chan(9), struct dma_chan_tbl_ent(9), dma_chan_is_local(9), dma_channel_rebalance(9), balance_ref_count(9), dma_chan_get(9), dma_chan_put(9), dma_find_channel(9), dma_issue_pending_all(9), dma_get_slave_channel(9), __dma_request_channel(9), dma_request_chan(9), dma_request_chan_by_mask(9), devm_dma_request_chan(9), dmaengine_get(9), dmaengine_put(9), dma_async_device_register(9), dma_async_device_unregister(9), dmaenginem_async_device_register(9), dma_wait_for_async_tx(9), dma_run_dependencies(9).

Catch you later, bestie 🫶 — this page comes from ./drivers/dma and is dated October 2026, still repping the min_chan(9) manual. Mwah 💋