pmbus_read_...c_block_data(9)

💅 pmbus_read_...c_block_data(9) 💅

okay so welcome to the Kernel API Manual, bestie — yes that's the actual manual name, we're in the big leagues now 🎀 this page is all about pmbus_read_smbus_i2c_block_data and honestly? she's a little baddie with a backup plan.

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✨ NAME ✨

pmbus_read_smbus_i2c_block_data — literally just here to Read SMBus/I2C block data 🦋

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🌸 SYNOPSIS 🌸

int pmbus_read_smbus_i2c_block_data (struct i2c_client *client , u8 reg
, char *data_buf );

like, that's the whole signature, no notes 💅

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🎀 ARGUMENTS 🎀

• client — the handle to the slave device. your main character connection fr 🫶
• reg — a byte that the slave gets to interpret. cryptic queen, we respect it 👑
• data_buf — the byte array where the data gets read into. she's the destination, she's holding the vibes 💖

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⭐ RETURN ⭐

either a negative errno (sad girl hours 😭) or the number of bytes read (slay 🌈).

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🔥 DESCRIPTION 🔥

So. This is a PMBus internal function whose whole job is reading a SMBus block from a PMBus chip, no cap.

Here's the tea: PMBus chips report all kinds of properties using SMBus block read operations. BUT — and this is the plot twist — not every I2C controller supports that operation. tragic, honestly 💀

So the function does this: execute SMBus block read if it's supported. If it's not supported, but SMBus I2C block read is supported, then use that instead. flexible icon behavior ✨

⚠️ but listen — note that at most 31 data bytes can be read from the device if i2c_smbus_read_i2c_block_data is used to read the data. This is a SMBUs protocol limit which can not be avoided. not us, not you, not anybody — it's just the rules 🙈

And if neither I2C_FUNC_SMBUS_READ_BLOCK_DATA nor I2C_FUNC_SMBUS_READ_I2C_BLOCK is supported, it returns -EOPNOTSUPP. both doors locked, she goes home 😔

🚨 important caveat bestie: callers must hold pmbus_lock or execute calls from the probe function. that is not optional, that's the vibe check and you must pass it 🧚

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🦋 SEE ALSO 🦋

• Kernel file ./drivers/hwmon/pmbus/pmbus_core.c — go read the source, iykyk 💜

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okay that's the page!! stay hydrated, hold your locks, and remember — ./drivers/hwmon/pmbus, October 2026, brought to you by the pmbus_read_...c_block_data(9) girlies 💖✨🎀