usb_free_noncoherent(9)

💅 usb_free_noncoherent — the usb_free_noncoherent(9) moment

okay so bestie, we're in the Kernel API Manual today and this one is genuinely a whole vibe — it's the cleanup function. the closer. the "ok we're done here, release the buffer" main character 💖

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🌸 NAME 🌸

usb_free_noncoherent — literally the function that frees memory allocated with usb_alloc_noncoherent(). that's it. that's the job. she's the undo button 🎀

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✨ SYNOPSIS ✨

void usb_free_noncoherent (struct usb_device *dev , size_t size , void
*addr , enum dma_data_direction dir , struct sg_table *table );

like, exactly that signature, no cap. void return, five args, copy it character for character or the compiler will simply not vibe with you 😭

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🦋 ARGUMENTS 🦋

• dev — the device the buffer was used with. the whole point, the moment, the context 👑
• size — the requested buffer size. yes you have to remember it. yes it has to be the same one 🍓
• addr — CPU address of buffer. the actual pointer bestie 💅
• dir — the DMA transfer direction. iconic enum, must match 🧚
• table — describes the allocated and DMA mapped memory, 💀 (yes the original had that trailing comma, I'm keeping her, she's part of the lore)

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🌈 DESCRIPTION 🌈

so what this actually does: it reclaims an I/O buffer, letting it be reused. giving it a second life. a little recycling era for your kernel memory ♻️✨

⚠️ but listen — the memory must have been allocated using usb_alloc_noncoherent, and the parameters must match those provided in that allocation request. no improvising. no "close enough". fr fr the values have to line up or you're in undefined-behaviour territory and that is not the slay you think it is 🙈

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🔥 SEE ALSO 🔥

kernel file ./drivers/usb/core/usb.c — and honestly the whole friend group showed up to this party:

• usb_find_common_endpoints(9)
• usb_find_common_endpoints_reverse(9)
• usb_find_endpoint(9)
• usb_check_bulk_endpoints(9)
• usb_check_int_endpoints(9)
• usb_find_alt_setting(9)
• usb_ifnum_to_if(9)
• usb_altnum_to_altsetting(9)
• usb_find_interface(9)
• usb_for_each_dev(9)
• usb_release_dev(9)
• usb_alloc_dev(9)
• usb_get_dev(9)
• usb_put_dev(9)
• usb_get_intf(9)
• usb_put_intf(9)
• usb_intf_get_dma_device(9)
• usb_lock_device_for_reset(9)
• usb_get_current_frame_number(9)
• usb_alloc_coherent(9)
• usb_free_coherent(9)
• usb_alloc_noncoherent(9)
• usb_endpoint_max_periodic_payload(9)
• usb_endpoint_is_hs_isoc_double(9)

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and that's the page!! no notes. sourced straight from ./drivers/usb/core, dated October 2026, page usb_free_noncoherent(9) — go free that buffer and hydrate bestie 🫶💜