cdc_parse_cdc_header(9)

🎀 cdc_parse_cdc_header — kernel API manual, but make it make sense 🎀

okay so bestie, welcome to the cdc_parse_cdc_header(9) glow-up ✨ this is the kernel API manual page, and we're gonna read it together like it's a group chat at 2am 💅

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✨ NAME ✨

cdc_parse_cdc_header — parse the extra headers present in CDC devices

like, it literally reads the little bonus headers that CDC devices are packing 🎀 no cap, that's the whole job.

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🌸 SYNOPSIS 🌸

int cdc_parse_cdc_header (struct usb_cdc_parsed_header *hdr , struct
usb_interface *intf , u8 *buffer , int buflen );

here's the vibe check: it returns an int, takes four things, and we're gonna meet all four right now 🫶

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💖 ARGUMENTS 💖

• hdr — the place to put the results of the parsing. this is the lil landing spot where all the parsed goodness gets dropped off 📦
• intf — the interface for which parsing is requested. like, which USB interface are we even doing this for, bestie 🦋
• buffer — pointer to the extra headers to be parsed. yes, pointer, it's giving main character energy ⭐
• buflen — length of the extra headers. because a buffer without a length is just chaos, and we don't do chaos 🙈

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👑 DESCRIPTION 👑

so what does it actually do, you ask? 🍓

This evaluates the extra headers present in CDC devices which bind the interfaces for data and control and provide details about the capabilities of the device.

that's it, that's the whole thing 🔥 it's the function that actually reads those extra headers and figures out what the device is capable of. iconic behaviour, honestly. not me being obsessed with a USB parsing function 😭

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🌈 RETURN 🌈

• number of descriptors parsed — slay 💅
• -EINVAL — if the header is contradictory beyond salvage 💀 like, it's so contradictory it cannot be saved. we tried. it's done. bye.

fr fr, if you get -EINVAL back the header was beyond rescue, don't go looking for a hidden meaning, there isn't one 🫶

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🧚 SEE ALSO 🧚

Kernel file ./drivers/usb/core/message.c plus this whole friend group of USB helpers, all present and accounted for 👑:

• usb_control_msg(9)
• usb_control_msg_send(9)
• usb_control_msg_recv(9)
• usb_interrupt_msg(9)
• usb_bulk_msg(9)
• usb_bulk_msg_killable(9)
• usb_sg_init(9)
• usb_sg_wait(9)
• usb_sg_cancel(9)
• usb_get_descriptor(9)
• usb_get_string(9)
• usb_string(9)
• usb_cache_string(9)
• usb_get_status(9)
• usb_clear_halt(9)
• usb_disable_endpoint(9)
• usb_reset_endpoint(9)
• usb_disable_interface(9)
• usb_disable_device(9)
• usb_enable_endpoint(9)
• usb_enable_interface(9)
• usb_set_interface(9)
• usb_reset_configuration(9)
• usb_set_wireless_status(9)
• usb_driver_set_configuration(9)

go read those next, iykyk 💜

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okay and finally, the cute lil sign-off 🎀 this page lives in the kernel file dir ./drivers/usb/core, and it's dated October 2026. that's the source, the version and the date, all wrapped up with a bow 💖 bye bestie, go parse some headers ✨