__i2c_transfer(9)

💖 __i2c_transfer(9) — unlocked i2c_transfer, no cap 💖

okay so welcome to the Kernel API Manual, bestie 🌸 — this is the page for __i2c_transfer, aka the unlocked flavor of i2c_transfer. It’s giving “I do the transfer, but you already brought the lock” energy 🦋✨.

💅 NAME 💅

__i2c_transfer — unlocked flavor of i2c_transfer 💖

✨ SYNOPSIS ✨

int __i2c_transfer (struct i2c_adapter *adap , struct i2c_msg *msgs ,
       int num );

🎀 ARGUMENTS 🎀

• adap — handle to the I2C bus. Like, your little bus portal 🔌✨
• msgs — one or more messages to execute before STOP is issued to terminate the operation; each message begins with a START. So yes: plural messages, each one starts with START, and the whole thing gets terminated with STOP 💅
• num — number of messages to be executed. Count ’em, bestie 🔢🌸

🌈 DESCRIPTION 🌈

Returns a negative errno, else the number of messages executed. So it’s either “nope, here’s an error” or “yep, here’s how many messages went through” 😭✨

🔒 Lock check, bestie: the adapter lock must be held when calling this function. No cap — that’s the whole unlocked-but-not-really vibe. You hold the lock, then call this 🫶

No debug logging takes place. None. Zero. It’s not logging, it’s just doing the thing 💀

🔥 SEE ALSO 🔥

Kernel file ./drivers/i2c/i2c-core-base.c and all these iconic little functions:

• i2c_verify_client(9)
• i2c_adapter_lock_bus(9)
• i2c_adapter_trylock_bus(9)
• i2c_adapter_unlock_bus(9)
• i2c_new_client_device(9)
• i2c_unregister_device(9)
• i2c_find_device_by_fwnode(9)
• i2c_new_dummy_device(9)
• devm_i2c_new_dummy_device(9)
• i2c_new_ancillary_device(9)
• i2c_verify_adapter(9)
• i2c_handle_smbus_host_notify(9)
• i2c_add_adapter(9)
• i2c_add_numbered_adapter(9)
• i2c_del_adapter(9)
• devm_i2c_add_adapter(9)
• i2c_find_adapter_by_fwnode(9)
• i2c_get_adapter_by_fwnode(9)
• i2c_parse_fw_timings(9)
• i2c_del_driver(9)
• i2c_transfer(9)
• i2c_transfer_buffer_flags(9)
• i2c_get_device_id(9)
• i2c_client_get_device_id(9)
• i2c_get_dma_safe_msg_buf(9)
• i2c_put_dma_safe_msg_buf(9)

xoxo, your kernel bestie 💅✨ this lil page lives in ./drivers/i2c, dated October 2026, and it’s literally __i2c_transfer(9). mwah 💋🎀