usb_altnum_to_altsetting(9)

✨ NAME ✨

okay so this is usb_altnum_to_altsetting(9) from the Kernel API Manual, and it’s literally here to get the altsetting structure with a given alternate setting number. that’s the whole vibe. 💅

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🎀 SYNOPSIS 🎀

struct usb_host_interface * usb_altnum_to_altsetting (const struct
usb_interface *intf , unsigned int altnum );

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🦋 ARGUMENTS 🦋

• intf — the interface that’s holding the altsetting in question 🫶
• altnum — the desired alternate setting number, aka the number you’re looking for ✨

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💅 DESCRIPTION 💅

so what it does is search the altsetting array of the specified interface for an entry with the correct bAlternateSetting value. lowkey iconic search behavior. 🔥

note bestie: altsettings need not be stored sequentially by number, so it would be incorrect to assume that the first altsetting entry in the array corresponds to altsetting zero. this routine helps device drivers avoid such mistakes. fr fr, don’t assume the order is cute and numbered — it’s not guaranteed. 😭

🚨 warning, no cap: Don’t call this function unless you are bound to the intf interface or you have locked the device!

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🌈 RETURN 🌈

a pointer to the entry of the altsetting array of intf that has altnum as the alternate setting number. NULL if not found. that’s it, that’s the return vibe. 💖

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🔥 SEE ALSO 🔥

kernel file: ./drivers/usb/core/usb.c — and these absolute icons are in the see-also circle:

• 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_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_free_noncoherent(9)
• usb_endpoint_max_periodic_payload(9)
• usb_endpoint_is_hs_isoc_double(9)

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xoxo, your Unix bestie 💖 — source/version: ./drivers/usb/core · date: October 2026 · page: usb_altnum_to_altsetting(9) 🎀