usb_free_coherent(9)

💅 usb_free_coherent(9) — from the Kernel API Manual, bestie ✨

Okay so real talk, this one's a little function with one very important job, and it lives in the Kernel API Manual. Buckle up 🎀

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🌸 NAME 🌸

usb_free_coherent — the function that frees memory you got from usb_alloc_coherent(). That's it. That's the whole vibe. It's the cleanup crew 🧹✨

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🦋 SYNOPSIS 🦋

void usb_free_coherent (struct usb_device *dev , size_t size , void
*addr , dma_addr_t dma );

Yes bestie, void return — it hands nothing back, it just does the thing 👑

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💖 ARGUMENTS 💖

• dev — the device the buffer was used with 🫶 like, which device was this memory for? That one.
• size — the requested buffer size 📏 the number you asked for originally, no cap.
• addr — the CPU address of the buffer 🧠 the address from the CPU's point of view.
• dma — the DMA address of the buffer 🚚 and this one's the address from the DMA side. Both addresses, both matter, don't skip either.

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✨ DESCRIPTION ✨

So what this does is it reclaims an I/O buffer, which lowkey means letting it be reused — the memory goes back into circulation, main character energy for the buffer, honestly ♻️💫

🚨 BUT. And this is the part where you listen to me: the memory must have been allocated using usb_alloc_coherent, and the parameters must match those provided in that allocation request. Like, exactly. Same size, same everything. Fr fr, no improvising, no "close enough" — if you didn't get it from usb_alloc_coherent or the params don't line up, you're not slaying, you're just asking for trouble 😭💀

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🔥 SEE ALSO 🔥

Kernel file ./drivers/usb/core/usb.c — and then a whole group chat of friends, iykyk 🫶:

• 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) ← literally the other half of this story, go read it 👀
• usb_alloc_noncoherent(9)
• usb_free_noncoherent(9)
• usb_endpoint_max_periodic_payload(9)
• usb_endpoint_is_hs_isoc_double(9)

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And that's the whole page, bestie 🎀 this one came out of ./drivers/usb/core, dated October 2026, and it's filed under usb_free_coherent(9) — periodt 💜✨