i2c_new_dummy_device(9)

💅 i2c_new_dummy_device(9) — the Kernel API Manual glow-up 🎀

okay so you're in the Kernel API Manual, section 9, and today's main character is i2c_new_dummy_device. she's not flashy, she's not doing the most, but bestie she is essential. let's get into it ✨

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✨ NAME ✨

i2c_new_dummy_device — returns you a brand new i2c device that's bound to a dummy driver. yeah, dummy. she's a stand-in and she KNOWS it 💅

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🌸 SYNOPSIS 🌸

struct i2c_client * i2c_new_dummy_device (struct i2c_adapter *adapter ,
       u16 address );

like... look at her. two args, one pointer out. clean. iconic. 🫶

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🦋 ARGUMENTS 🦋

• adapter — the adapter that's managing the device, i.e. the boss of this whole situation ✨
• address — the seven bit address you want to use (seven bits, not eight, don't come for me)

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💜 CONTEXT 💜

can sleep 😴 — yes bestie, this one's allowed to nap. schedule accordingly.

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🔥 DESCRIPTION 🔥

So what does she actually do? She returns you an I2C client that's bound to the "dummy" driver. and why would you want a dummy, you ask? because some devices out here are greedy and consume multiple addresses. examples of these chips include various EEPROMS — like the 24c04 and 24c08 models, iykyk 🍓

These dummy devices have two main uses, and honestly both of them ate:

1. most I2C and SMBus calls except i2c_transfer need a client handle — and the dummy is gonna be that handle, periodt 💅
2. it stops that specified address from getting bound to a different driver. she's holding the spot. no cap. 🚫

And what do you get back? either:

• the new i2c client — and you should save it for later so you can use it with i2c_unregister_device (don't lose her, she's yours now 😭), or
• an ERR_PTR describing the error 💀

fr fr: check that return value. ERR_PTR is out here and she is not subtle about it.

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🌈 SEE ALSO 🌈

Kernel file ./drivers/i2c/i2c-core-base.c + the whole friend group:

• 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)
• 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(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)

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and that's the whole page bestie, you ate that 🫶💖

source location: ./drivers/i2c  ·  date: October 2026  ·  manual: i2c_new_dummy_device(9) — mwah, see you in the next manpage 🎀🦋✨