acm_cdc_notify(9)

💅 acm_cdc_notify — the "issue CDC notification to host" girlie 💅

okay so real talk, this is a page from the Kernel API Manual, section 9, and it's all about acm_cdc_notify. yes bestie, that's the whole name. she's niche, she's specific, she's serving exactly one job and she does it flawlessly. 🎀

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✨ SYNOPSIS ✨

int acm_cdc_notify (struct f_acm *acm , u8 type , u16 value , void *data
, unsigned length );

like, look at her. five params, one int return, no notes. iconic behavior honestly. 🌸

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🫶 ARGUMENTS 🫶

• acm — this is the struct f_acm * that wraps the host you're notifying. she's the main character of this whole operation, lowkey. 👑
• type — the notification type. that's it, that's the vibe. 🌈
• value — fr fr, just refer to the CDC specs for this one — it's the wValue field. iykyk. 📖
• data — the actual data to be sent. the payload. the moment. ✨
• length — the size of data. keep it accurate bestie, no guessing. 📏

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🦋 CONTEXT 🦋

okay this is the part where you gotta read the room before you call her. when acm_cdc_notify runs, all of this needs to be true:

• irqs blocked 🙈
• acm->lock held 🔒
• acm_notify_req non-null ✅

no cap, if you roll up in the wrong context she will not be happy with you. do the vibe check first. 💀

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💖 DESCRIPTION 💖

she returns zero on success, or a negative errno if things went sideways. clean, simple, no drama.

and if you're wondering what notification she's even issuing — go read section 6.3.5 of the CDC 1.1 specification. because there's literally only one notification we ever issue: SerialState change. that's it. that's the one. periodt. 💅🔥

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🌟 SEE ALSO 🌟

• kernel file ./drivers/usb/gadget/function/f_acm.c — go read the source bestie, she's right there 🧚

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and that's the whole page! stay hydrated, keep your locks held, and remember: this came to you from ./drivers/usb/gadget/function, dated October 2026, living in the Kernel API Manual. mwah 💜🍓