usb_free_urb(9)

✨ usb_free_urb ✨

okay bestie, so this is a page from the Kernel API Manual and it's literally the cleanup era of a urb's life. yes, we're freeing memory, but like... politely, and only when everyone is done. no cap.

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🌸 NAME 🌸

usb_free_urb — frees the memory used by a urb when all users of it are finished

it's giving ✨responsible memory management✨ and honestly? iconic.

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🎀 SYNOPSIS 🎀

void usb_free_urb (struct urb *urb );

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💅 ARGUMENTS 💅

• urb — pointer to the urb to free, and yes it may be NULL 👑. so go ahead and pass NULL, it's fine, no drama.

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🦋 DESCRIPTION 🦋

okay so here's the vibe: you must call this when a user of a urb is finished with it. like, must must. not optional, not "later maybe", we are calling it, periodt.

and when the last user of that urb calls this function? that's when the memory of the urb is actually freed 🫶. so it's a whole group-chat situation — everybody has to leave before the chat gets deleted, you know? the last one out frees the memory, fr fr.

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🌈 NOTE 🌈

⚠️ careful bestie, plot twist: the transfer buffer associated with the urb is not freed unless the URB_FREE_BUFFER transfer flag is set 💀. like, the urb goes away but the buffer is still there living its best life. so if you thought this freed everything, no. check your flags, iykyk.

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⭐ SEE ALSO ⭐

the Kernel file lives at ./drivers/usb/core/urb.c, and here's the whole bestie squad of related functions 🧚:

• usb_init_urb(9)
• usb_alloc_urb(9)
• usb_get_urb(9)
• usb_anchor_urb(9)
• usb_unanchor_urb(9)
• usb_pipe_type_check(9)
• usb_urb_ep_type_check(9)
• usb_submit_urb(9)
• usb_unlink_urb(9)
• usb_kill_urb(9)
• usb_poison_urb(9)
• usb_block_urb(9)
• usb_kill_anchored_urbs(9)
• usb_poison_anchored_urbs(9)
• usb_unpoison_anchored_urbs(9)
• usb_anchor_suspend_wakeups(9)
• usb_anchor_resume_wakeups(9)
• usb_wait_anchor_empty_timeout(9)
• usb_get_from_anchor(9)
• usb_scuttle_anchored_urbs(9)
• usb_anchor_empty(9)

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and that's the whole page! tysm for reading, go free your urbs responsibly 💖✨🌸🫶

— brought to you by ./drivers/usb/core, dated October 2026, and like... a whole lot of kernel love 🔥👑