ljca_event_cb_t(9)

💅 ljca_event_cb_t(9) — like, the whole vibe check

okay so bestie, welcome to the Kernel API Manual ✨ this one's a function-signature page, aka the "what shape does my callback have to be" page. it's short, it's sweet, it's iconic. let's go 🫶

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✨ NAME ✨

ljca_event_cb_t — the event callback function signature 🎀 like, the actual shape of the function you gotta write if you want in on the event tea.

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🌸 SYNOPSIS 🌸

void ljca_event_cb_t (void *context , u8 cmd , const void *evt_data ,
int len );

no cap, that's the whole signature. memorize it, screenshot it, put it on your fyp 💖

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🦋 ARGUMENTS 🦋

• context — the execution context of whoever registered this callback 💅 it's your little bag of stuff, you know exactly what's in it (or at least you should, bestie 🙈)
• cmd — the command from the device for this event 🎀 that's a u8, so tiny, so precious
• evt_data — the event data payload ✨ here's your tea, piping hot
• len — the event data payload length ⭐ so you know exactly how much tea you're holding

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🔥 DESCRIPTION 🔥

okay so this is the important bit, listen up 👑

The callback function is called in interrupt context, and the data payload is only valid during the call. If the user needs later access of the data, it must copy it.

🚨 bestie I cannot stress this enough — that pointer is on borrowed time. the moment your callback returns, evt_data is gone-gone. if you're gonna touch it later, copy it first. no exceptions, periodt. 💀

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🧚 SEE ALSO 🧚

Kernel file ./include/linux/usb/ljca.h — that's the home base, the mothership, the main character 💜

• struct ljca_client(9)
• struct ljca_gpio_info(9)
• struct ljca_i2c_info(9)
• struct ljca_spi_info(9)
• ljca_register_event_cb(9)
• ljca_unregister_event_cb(9)
• ljca_transfer(9)
• ljca_transfer_noack(9)

like, read them all, they're all kind of a vibe 🌈

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and that's the page, bestie!! 🎀 big slay energy, short and sweet. this one lives in ./include/linux/usb and it's dated October 2026 — so yeah, it's from the future, she's that girl 💫 go forth and copy your payloads 💖✨