i2c_smbus_write_byte_data(9)

💅 i2c_smbus_write_byte_data — bestie, it's in the Kernel API Manual ✨

Okay so picture this: you're deep in the kernel, you've got a tiny little sensor on an I2C bus, and you justтаки need to yeet one single byte at it. That's literally this function's whole personality. Welcome to the SMBus "write byte" protocol, no cap. 🎀

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✨ SYNOPSIS ✨

s32 i2c_smbus_write_byte_data (const struct i2c_client *client , u8
command , u8 value );

Yep, that's the whole signature — s32 going in, three args going out, and it's giving "small but mighty" energy. 🔥

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🌸 ARGUMENTS 🌸

• client — your handle to the slave device, like the contact in your phone you're about to text. It's a const struct i2c_client *, so hands off, don't go mutating it. 🫶
• command — a byte that the slave gets to interpret. You don't decide what it means, bestie — that's between the device and its datasheet. 💀
• value — the actual byte you're writing. The star of the show. The moment. 👑

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💖 DESCRIPTION 💖

This right here executes the SMBus "write byte" protocol. It returns a negative errno if things go sideways, or zero on success. That's it. That's the whole vibe check: < 0 means sad girl hours 😭, 0 means slay. ✨

Lowkey important: success is 0, not a count of bytes or anything cute like that. Negative errno = problem. Don't overthink it. 💅

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🦋 SEE ALSO 🦋

Kernel file ./drivers/i2c/i2c-core-smbus.c — that's where the actual implementation lives, go read it, it's iconic. And the whole friend group:

• i2c_smbus_pec(9)
• i2c_smbus_read_byte(9)
• i2c_smbus_write_byte(9)
• i2c_smbus_read_byte_data(9)
• i2c_smbus_read_word_data(9)
• i2c_smbus_write_word_data(9)
• i2c_smbus_read_block_data(9)
• i2c_smbus_write_block_data(9)
• i2c_smbus_xfer(9)
• i2c_smbus_read_i2c_block_data_or_emulated(9)
• i2c_new_smbus_alert_device(9)

Every single one of them, accounted for, not a single bestie left behind. 🌈

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And that's the whole page, babes! 🌸 This little gem lives under ./drivers/i2c in the Kernel API Manual, dated October 2026. Go forth and write your bytes. Mwah. 💜🧚⭐