i2c_atr_add_adapter(9)

💅 i2c_atr_add_adapter (kernel API manual, bestie edition)

okay so you found i2c_atr_add_adapter in the kernel API manual and you're like "what is this diva doing" — don't worry, I gotchu. She's a little function with main character energy and she's about to spawn a whole new I2C bus for you. ✨

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🌸 NAME 🌸

i2c_atr_add_adapter — create a child ("downstream") I2C bus. literally birthing a bus, no cap 🦋

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✨ SYNOPSIS ✨

int i2c_atr_add_adapter (struct i2c_atr *atr , struct i2c_atr_adap_desc
*desc );

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🎀 ARGUMENTS 🎀

• atr — the I2C ATR. the parent, the origin story, the whole vibe. 👑
• desc — an ATR adapter descriptor. it's giving "here's the blueprint for your new baby bus". 🍼

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💖 DESCRIPTION 💖

so after you call this function, a brand new i2c bus just appears. pop! iconic. adding and removing devices on that downstream bus will result in calls to the i2c_atr_ops->attach_client and i2c_atr_ops->detach_client callbacks — that's how the driver gets to assign an alias to the device. teamwork, bestie. 🫶

the adapter's fwnode is set to bus_handle, OR — plot twist — if bus_handle is NULL, the function goes looking for a child node whose 'reg' property matches the chan_id under the i2c-atr device's 'i2c-atr' node. detective era. 🔍

and when you're done with your new bus? call i2c_atr_del_adapter to remove the adapter. clean up after yourself, we love a responsible queen. 💅

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⭐ RETURN ⭐

0 on success, a negative error code otherwise. that's it, that's the vibe check. 😌

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🌈 SEE ALSO 🌈

kernel file ./include/linux/i2c-atr.h, plus the whole squad:

• enum i2c_atr_flags(9)
• struct i2c_atr_ops(9)
• struct i2c_atr_adap_desc(9)
• i2c_atr_new(9)
• i2c_atr_delete(9)
• i2c_atr_del_adapter(9)
• i2c_atr_set_driver_data(9)
• i2c_atr_get_driver_data(9)

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💀 and that's the page, bestie — straight from ./include/linux, dated October 2026, i2c_atr_add_adapter(9). go forth and add those adapters fr fr. 🧚💜